JP6948564B2 - Battery module - Google Patents

Description

The present invention relates to a battery module.

In recent years, secondary batteries such as lithium-ion secondary batteries have been used as portable power sources for personal computers, mobile terminals, etc., and vehicle drive power sources for electric vehicles (EV), hybrid vehicles (HV), plug-in hybrid vehicles (PHV), etc. It is preferably used in.

In a vehicle drive power supply application, a secondary battery is generally used in the form of a battery module in which a plurality of battery cells (cells) are connected in order to increase the output. In the battery module, a restraint load is applied in the direction perpendicular to the electrode surface in the battery cell in order to prevent the position shift of the battery cell due to vibration, impact, etc. when the vehicle is running, and to secure the battery characteristics, battery life, etc. There is a need to. Therefore, a general configuration of a battery module is a laminated body in which a plurality of battery cells are laminated, a pair of end plates arranged at both ends in the stacking direction of the laminated body, and a restraining load between the pair of end plates. It is provided with a restraint member to which the above is applied.

As the restraint member, a structure using a restraint band, a structure using a restraint load holding member, and a structure using a bolt or a nut are well known. Specifically, for example, Patent Document 1 discloses a configuration in which a laminated body of battery cells is sandwiched between end plates and a restraining load is applied by a tape-shaped band made of synthetic resin. In Patent Document 2, a laminated body of battery cells is sandwiched between end plates having through holes, restraining rods as restraining load holding members are arranged on both sides of the laminated body, and the end plates are tightened with nuts or bolts. Discloses a configuration in which a restraining load is applied.

Japanese Unexamined Patent Publication No. 06-036794 Japanese Patent No. 5481796

It is known that a secondary battery expands and contracts due to a change in the state of charge or the like. Therefore, when used as a battery module, when the battery cell expands and contracts depending on the usage environment, the dimensions of the battery cell and the reaction force of the restraint load change, and the dimensions and the restraint load of the restraint member of the battery module change accordingly. .. Therefore, the restraint member secures the minimum restraint load required when the battery cell contracts to the minimum, and the reaction force of the restraint load generated when the battery cell expands to the maximum does not exceed the allowable stress of the restraint member. Need to be designed for.
On the other hand, in recent years, all-solid-state batteries using solid electrolytes have been developed. An all-solid-state battery requires a higher restraining load than a conventional secondary battery using an electrolytic solution. Therefore, in a configuration in which a tape-shaped band made of synthetic resin as described in Patent Document 1 is used for the restraint member, it is necessary to increase the thickness of the restraint member or the like in order to withstand a high restraint load. As a result, the volume of the battery module is increased.
Further, in the configuration in which the restraint load holding member and the nut or bolt are used as the restraint member as described in Patent Document 2, the fracture stress (tensile stress) of high-tensile steel or the like is high in order to withstand the high restraint load. A metal material is used for the restraint member. However, in a metal material having a high fracture stress, the elastic modulus generally increases with the fracture stress. When the restraint member is made of metal having a high elastic modulus, when the battery cell expands, the restraint member cannot follow the expansion of the battery cell because the restraint member is inflexible. The stress increases. Therefore, when the battery cell is expanded, the maximum restraint load becomes very high. When designing a restraint member that can withstand this high restraint load, it is necessary to increase the dimensions of the restraint member, resulting in an increase in the volume of the battery module.

Therefore, an object of the present invention is to provide a battery module capable of applying a sufficient restraint load even if the volume of the restraint member is small.

In the battery module disclosed herein, a restraining load is applied between a laminated body in which a plurality of battery cells are laminated, a pair of end plates arranged at both ends in the stacking direction of the laminated body, and the pair of end plates. It is provided with a restraining member. The restraining member includes a resin material having an elastic modulus of 2 GPa or more and a strain amount of 3% or more in the elastic deformation region.

According to such a configuration, by using a resin material restraining member having an elastic modulus of 2 GPa or more and a strain amount of 3% or more in the elastic deformation region, a sufficient restraining load is obtained even when the battery cell is contracted. Can be applied, and the restraint load (maximum restraint load) in the expanded state of the battery cell can be reduced. Therefore, it is possible to avoid the problem of the required increase in volume due to the increase in the maximum restraint load. Therefore, according to such a configuration, it is possible to provide a battery module capable of applying a sufficient restraint load even if the volume of the restraint member is small.

It is a schematic diagram (top view) which shows the structure of the battery module which concerns on one Embodiment of this invention. It is a perspective view which shows an example of the end plate and the restraint member of the battery module which concerns on one Embodiment of this invention. The relationship between the distance between end plates and the restraint load is shown for a battery cell in a low charge state, a battery cell in a high charge state, an example of a battery module according to an embodiment of the present invention examined, and an example of a battery module of the prior art. It is a graph. It is a schematic diagram (top view) which shows the structure of the battery module of the example of the prior art examined. (A) to (D) are diagrams (top view) schematically showing an example of a procedure for manufacturing a battery module according to an embodiment of the present invention.

Hereinafter, embodiments according to the present invention will be described with reference to the drawings. It should be noted that matters other than those specifically mentioned in the present specification and necessary for carrying out the present invention (for example, general configurations and manufacturing processes of battery cells and battery modules that do not characterize the present invention) are included. , Can be grasped as a design matter of a person skilled in the art based on the prior art in the field. The present invention can be carried out based on the contents disclosed in the present specification and common general technical knowledge in the art. Further, in the following drawings, members / parts having the same action 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.

FIG. 1 is a schematic view showing the structure of the battery module 100 according to the present embodiment, and is a top view (top view) of the battery module 100. FIG. 2 is a perspective view showing an example of the end plate 30 and the restraint member 40 of the battery module 100 according to the present embodiment. In FIG. 2, the description of the laminated body 20 is omitted.

As shown in FIG. 1, the battery module 100 according to the present embodiment includes a laminated body 20 in which a plurality of battery cells 10 are laminated, and a pair of end plates 30 arranged at both ends of the laminated body 20 in the stacking direction. A restraint member 40 for applying a restraint load between the pair of end plates 30 is provided.

The laminated body 20 is configured by laminating a plurality of battery cells 10 with the direction of the arrow L in FIG. 1 as the laminating direction. The plurality of battery cells 10 are electrically connected in series or in parallel. A member other than the battery cell 10 (for example, a cooling plate or the like) may be interposed between the plurality of battery cells 10.
The battery cell 10 used in the laminate 20 is preferably an all-solid-state battery, and more preferably an all-solid-state lithium secondary battery. All-solid-state batteries typically include a positive electrode, a negative electrode, and a solid electrolyte. When the battery cell 10 is an all-solid-state battery, the stacking directions of the positive electrode, the negative electrode, and the solid electrolyte are the same as the stacking direction L of the battery cell 10. The battery cell may be a non-aqueous electrolyte secondary battery. The non-aqueous electrolyte secondary battery includes a positive electrode, a negative electrode, a separator, and a non-aqueous electrolyte. When the battery cell 10 is a non-aqueous electrolyte secondary battery, the stacking directions of the positive electrode, the negative electrode, and the separator are the same as the stacking direction L of the battery cell 10. Therefore, a restraining load is applied in the direction perpendicular to the electrode surface in the battery cell 10.
In the present specification, the "secondary battery" generally refers to a power storage device capable of being repeatedly charged and discharged, and is a term including a so-called storage battery and a power storage element such as an electric double layer capacitor.

The end plate 30 receives the restraining load of the restraining member 40 and the reaction pressure of the restraining load of the laminated body 20. Therefore, the end plate 30 is made of a material and a shape that can withstand these stresses. The end plate 30 may be made of metal or resin, for example, carbon steel. In the illustrated example, the end plate 30 has a plate shape.
As shown in FIG. 2, the end plate 30 has holes on the long side surface when the laminated body 20 is the main surface (that is, the surface perpendicular to the surface facing the laminated body 20 and including the long side). 32 may have. This hole 32 is used when manufacturing the battery module 100, as will be described later.

As shown, the restraint member 40 has a band shape so that a restraint load can be applied between the pair of end plates 30. More specifically, the restraint member 40 has a rectangular ring shape. However, the shape of the restraint member 40 is not limited to this, and may be appropriately determined according to the required restraint load and the dimensions of the battery module 100.
In the illustrated example, three restraint members 40 are used. However, the number of the restraint members 40 is not limited to this, and may be appropriately determined according to the required restraint load and the dimensions of the battery module 100.

The restraint member 40 includes a resin material having an elastic modulus of 2 GPa or more and a strain amount of 3% or more in the elastic deformation region.
The elastic modulus and the amount of strain in the elastic deformation region can be measured using, for example, a tensile tester.
The type of resin material is not particularly limited as long as the elastic modulus is 2 GPa or more and the strain amount in the elastic deformation region is 3% or more.
The resin material is preferably a resin material containing a fiber component and a resin component, and more preferably a fiber reinforced resin (fiber reinforced plastic). Epoxy resin is preferable as the resin component constituting the resin material. As the fiber component constituting the resin material, glass fiber and carbon fiber are preferable. The orientation angle of the fiber component is preferably 25 ° or more and 65 ° or less, more preferably 30 ° or more and 60 ° or less, and more preferably 35 ° or more and 55 ° or less. Here, the orientation angle is an angle formed by the longitudinal direction of the fiber and one side of the resin material.

FIG. 3 shows the results of actual examination of the battery module 100 according to the present embodiment and the conventional battery module. FIG. 3 shows the relationship between the distance between end plates and the restraint load for a battery cell in a low charge state, a battery cell in a high charge state, an example of a battery module according to the present embodiment examined, and an example of a conventional battery module. It is a graph which shows.

The two downward-sloping straight lines (inclination is negative) in FIG. 3 show the relationship between the end plate distance (battery stack length) and the restraint load for the battery cells in the low charge state and the high charge state. When comparing the low charge state and the high charge state, the battery cell in the high charge state is inflated, so a higher restraint load is required even if the distance between the end plates is the same as shown by the two straight lines. It becomes.

The two straight lines rising to the right (inclination is positive) in FIG. 3 are those of the battery module of the example of the present embodiment and the battery module of the example of the prior art.
The battery module of the example of this embodiment has the above-described configuration shown in FIG. As the end plate 30, an end plate (t = 34 mm) made of S45C was used. Further, as the restraint member 40, a restraint member (t = 9 mm) in which a carbon fiber reinforced resin was formed into a rectangular annular shape was used. The elastic modulus of this carbon fiber reinforced resin was 2 GPa or more, and the amount of strain in the elastically deformed region was 3% or more.
The battery module of the prior art example has the configuration shown in FIG. FIG. 4 is a schematic view (top view) showing the structure of the battery module 700 of the example of the prior art. The battery module 700 of the conventional example includes a stack of a plurality of battery cells 620 and a pair of end plates 630 that sandwich the stack 620. The battery module 700 includes a pair of restraint load holding members 640 between the pair of end plates 630 and on both sides of the laminated body 620. The battery module 700 further includes a bolt 660, and has a configuration in which the end plate 630 and the restraint load holding member 640 are fastened with the bolt 660 to restrain the battery module 700. As the end plate 630, an end plate (t = 20 mm) made of A6061-t6 was used. As the restraint load holding member 640, a restraint load holding member (t = 9 mm) made of A6061-t6 was used.

The battery module of the example of the present embodiment and the battery module of the example of the prior art are designed so that the restraint load in the low charge state is 200 kN at a predetermined distance between the end plates. Therefore, the straight line of the example of the present embodiment and the straight line of the example of the prior art intersect at the same point as the straight line of the battery cell in the low charge state, and the restraint load at this point is 200 kN.

On the other hand, the straight line of the battery module in the example of the prior art has a large inclination, and intersects the straight line of the battery cell in the highly charged state at a point where the restraint load is about 600 kN. Since the battery cell in the highly charged state is inflated, the restraint load is maximized. Therefore, this indicates that the maximum constraining load of the battery module of the prior art example is about 600 kN.
On the other hand, the straight line of the battery module of the example of the present embodiment has a small inclination and intersects the straight line of the battery cell in the highly charged state at a point where the restraint load is about 300 kN. This indicates that the maximum restraint load of the battery module of the example of this embodiment is about 300 kN.
From the above, it can be seen that the maximum restraint load of the battery module of the example of the present embodiment is much smaller than the maximum restraint load of the battery module of the example of the prior art.

Therefore, in the present embodiment, the battery cell 10 shrinks to the minimum by forming the restraint member 40 using a resin material having an elastic modulus of 2 GPa or more and a strain amount of 3% or more in the elastic deformation region. It is possible to secure the minimum restraint load required when the load is applied. In addition, the maximum load when the battery cell 10 expands to the maximum can be reduced, thereby avoiding the problem of the required increase in volume due to the increase in the maximum restraint load.
That is, according to the battery module 100 according to the present embodiment, a sufficient restraint load can be applied even if the volume of the restraint member is small.

Next, an example of a method for manufacturing the battery module 100 according to the present embodiment will be described. FIG. 5 schematically shows an example of a manufacturing procedure of the battery module 100 according to the present embodiment. FIG. 5 is a top view as in FIG. 1.

First, as shown in FIG. 5A, a pair of end plates 30 are set inside the rectangular annular restraint member 40.
Next, as shown in FIG. 5 (B), the metal rod-shaped jig 50 is inserted into the hole 32 (see FIG. 2) of the end plate 30. Then, the rod-shaped jig 50 is pulled in the direction of the arrow to apply a tensile load. Due to this tensile load, the restraint member 40 extends and the ring expands.
Next, as shown in FIG. 5C, the laminated body 20 in which a plurality of battery cells 10 (see FIG. 1) are laminated is set inside the restraint member 40 and the pair of end plates 30. At this time, each battery cell 10 is kept in a low charge state.
Next, as shown in FIG. 5D, the rod-shaped jig 50 is removed from the hole of the end plate 30 to release the tensile load. The restraint member 40 is elastically deformed to eliminate the expansion of the ring, and a restraint load is generated. As a result, the laminated body 20 sandwiched between the pair of end plates 30 is restrained, and the battery module 100 according to the present embodiment is obtained.
The method for manufacturing the battery module 100 according to the present embodiment is not limited to the above example, and may be manufactured by other methods.

The battery module 100 configured as described above can be used for various purposes. Suitable applications include vehicle drive power sources for electric vehicles (EVs), hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs) and the like. The battery module 100 can also be used as a portable power source for personal computers, mobile terminals, and the like.

Although specific examples of the present invention have been described in detail above, these are merely examples and do not limit the scope of claims. The techniques described in the claims include various modifications and modifications of the specific examples illustrated above.

10 Battery cell 20 Laminated body 30 End plate 32 Hole 40 Restraint member 50 Rod-shaped jig 100 Battery module

Claims (2)

A laminated body in which multiple battery cells are laminated, and
A pair of end plates arranged at both ends in the stacking direction of the laminated body,
A restraining member that applies a restraining load between the pair of end plates,
It is a battery module equipped with
The restraining member is a rectangular annular member formed by molding a resin material having an elastic modulus of 2 GPa or more and a strain amount of 3% or more in an elastic deformation region.
The resin material is a fiber-reinforced resin containing a fiber component and a resin component.
The orientation angle of the fiber component is 25 ° or more and 65 ° or less.
A restraining load of at least 200 kN is applied,
Battery module. The fiber component of the resin material is glass fiber or carbon fiber.
The resin component of the resin material is an epoxy resin.
The battery module according to claim 1.

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