JP7735110B2 - Battery cushioning material - Google Patents

Description

The present invention relates to a cushioning material for batteries. More specifically, it relates to a cushioning material for batteries such as secondary batteries used in electric vehicles.

Batteries (secondary batteries) have traditionally been widely used as energy sources for electric vehicles and other devices. These batteries include multiple battery cells and cushioning material (battery cushioning material). Known battery cell configurations include an electrode assembly made by stacking a positive electrode, a negative electrode, and a separator, with this electrode assembly housed in a storage case.

This battery is equipped with a restraining section that stacks multiple storage cases, each containing an electrode assembly, and restrains them in the stacking direction. This restraining section is positioned on the outside of the storage cases and restrains the storage cases from the outside.

And with multiple storage cases restrained by the restraint section, such batteries expand and contract due to heat generated during charging and discharging.

The electrodes are subjected to a load due to expansion caused by this charging and discharging, but cushioning materials (battery cushioning materials) are used to prevent the electrodes from being damaged by this load (see, for example, Patent Document 1). Cushioning materials are also effectively used to reduce shocks when the battery is vibrated, in addition to preventing the expansion caused by charging and discharging.

Japanese Patent Application Laid-Open No. 2020-4556

However, cushioning materials such as the buffer sheet of Patent Document 1 still have room for further improvement. Specifically, cushioning materials such as the buffer sheet of Patent Document 1 generate a large reaction force as the amount of compression due to an external force such as a load increases, and in particular, once a certain amount of compression is exceeded, a large reaction force tends to occur suddenly (see Figure 13). When a large reaction force (especially a sudden large reaction force) occurs, a large force tends to be applied to the object being cushioned (for example, the storage case in the case of a battery). Therefore, even if a large external force is applied and the amount of compression increases, conventional cushioning materials still have room for improvement in terms of suppressing the increase in reaction force and making it less likely for a large reaction force to occur.

The present invention was made in light of these conventional technologies, and its objective is to develop a cushioning material for batteries that suppresses an increase in reaction force within a specified range of compression.

According to the present invention, the following battery cushioning material is provided.

[1] A device having an upper side portion, a lower side portion, and a plurality of connecting portions connecting the upper side portion and the lower side portion,
the connecting portion is made of an elastic material,
the connecting portion has one surface at its base portion that is curved and the other surface that is flat, or one surface and the other surface at the base portion that are curved and have different radii of curvature;
When an external force of a predetermined magnitude or greater is applied so that the upper edge portion and the lower edge portion approach each other, the connecting portion buckles, thereby suppressing an increase in the reaction force.

[ 2 ] When one surface of the connecting portion at its base portion is a curved surface and the other surface is a flat surface, the flat surface is located on the outer side,
The cushioning material for a battery according to [ 1 ] above, wherein when the curved surfaces have different radii of curvature, the surface located on the outside has a smaller radius of curvature.

[ 3 ] The cushioning material for a battery according to [1] or [2] , wherein the connecting portion is formed from a pair of connecting bodies.

[ 4 ] The battery cushioning material according to any one of [1] to [ 3 ], wherein the connecting portion has a rib attached to the center.
[5] A device having an upper side portion, a lower side portion, and a plurality of connecting portions connecting the upper side portion and the lower side portion,
the connecting portion is made of an elastic material,
The connecting portion has a rib attached to the center thereof,
When an external force of a predetermined magnitude or greater is applied so that the upper edge portion and the lower edge portion approach each other, the connecting portion buckles, thereby suppressing an increase in the reaction force.

When an external force greater than a predetermined level is applied to the battery cushioning material of the present invention, causing the upper and lower edges to approach each other, the connecting parts made of elastic material buckle, thereby maintaining the reaction force within a predetermined range of compression and preventing an increase in the reaction force.

1 is a cross-sectional view schematically showing a state in which one embodiment of the cushioning material for a battery of the present invention is used. FIG. 3 is a cross-sectional view schematically showing another state of use of the embodiment of the cushioning material for a battery of the present invention. 1 is a perspective view schematically illustrating one embodiment of a cushioning material for a battery of the present invention. 1 is a partial plan view schematically illustrating a part of one embodiment of a cushioning material for a battery of the present invention. 5 is an explanatory diagram showing a state in which an external force is applied to the battery cushioning material shown in FIG. 4. FIG. FIG. 10 is a partial plan view schematically illustrating a part of another embodiment of the cushioning material for a battery of the present invention. FIG. 10 is a partial plan view schematically showing a part of still another embodiment of the cushioning material for a battery of the present invention. FIG. 10 is a partial plan view schematically showing a part of still another embodiment of the cushioning material for a battery of the present invention. FIG. 10 is a partial plan view schematically showing a part of still another embodiment of the cushioning material for a battery of the present invention. 10 is an explanatory diagram showing a state in which the battery cushioning material shown in FIG. 9 is subjected to an external force. FIG. 10 is a graph showing the relationship between compression amount and reaction force in analysis result 1. 10 is a graph showing the relationship between the compression amount and the reaction force in analysis result 2. 10 is a graph showing the relationship between the amount of compression and the reaction force in Reference Example 1. FIG. 1 is a perspective view schematically illustrating a conventional cushioning material for a battery.

Embodiments of the present invention will be described below with reference to the drawings. It should be understood that the present invention is not limited to the following embodiments, and that appropriate design changes and improvements may be made based on the common knowledge of those skilled in the art without departing from the spirit of the present invention.

(1) Battery cushioning material:
One embodiment of the battery cushioning material of the present invention is a battery cushioning material 100 shown in Figures 3 and 4. The battery cushioning material 100 has an upper edge portion 11, a lower edge portion 13, and a plurality of connecting portions 10 connecting the upper edge portion 11 and the lower edge portion 13, and the connecting portions 10 are made of an elastic material. When an external force of a predetermined magnitude or greater is applied to the battery cushioning material 100 so as to bring the upper edge portion 11 and the lower edge portion 13 closer to each other, the connecting portions 10 buckle, thereby suppressing an increase in the reaction force.

When this type of battery cushioning material 100 receives an external force that brings the upper edge 11 and lower edge 13 closer together, it elastically deforms to absorb the external force. When an external force greater than a predetermined level is applied, the connecting portion 10, made of an elastic material, buckles (see Figure 5), thereby maintaining the reaction force within a predetermined range of compression and suppressing an increase in the reaction force. In other words, the connecting portion 10 deliberately buckles when a predetermined compression amount is reached, suppressing an increase in the reaction force.

The battery cushioning material 100 can be used as a cushioning material placed between adjacent battery cells 210 among a plurality of battery cells 210, for example, as shown in Figure 1.

As shown in Figure 13, rubber, the main material used in cushioning materials, tends to be easily deformed when compressed in areas where distortion is small (when the amount of compression is small), and therefore tends not to generate sufficient reaction force. On the other hand, in areas where distortion is large (when the amount of compression is large), the more the rubber distorts, the more the volume is compressed, and the reaction force tends to increase sharply (see Figure 13). As such, conventional cushioning rubber products that use rubber as their main ingredient have been unable to generate the desired sufficient reaction force while maintaining that reaction force constant over a wide compression range (in other words, suppressing the increase in reaction force).

The battery cushioning material of the present invention generates a desired, sufficient reaction force while maintaining that reaction force constant over a wide compression range (in other words, suppressing an increase in reaction force). That is, as shown in Figure 12, for example, when a predetermined amount of compression is reached, i.e., when a predetermined load is applied, the connecting portion 10 buckles, suppressing an increase in the load. Even after buckling, the connecting portion 10 continues to function as a spring, reducing the sudden drop in reaction force that occurs after buckling (see Figure 12, for example).

There are no particular restrictions on the shape of the battery cushioning material 100, but it is preferable that it be flat, and its thickness can be set appropriately taking into account the space in which the battery cushioning material 100 will be placed, etc.

The size of the battery cushioning material 100 is not particularly limited and can be set as appropriate. When it is adjacent to the battery cell 210, it can be the same size as the battery cell 210 or slightly smaller than the battery cell 210.

(1-1) Connecting part:
The connecting portions 10 are made of an elastic material and connect the upper edge portion 11 and the lower edge portion 13. A plurality of connecting portions 10 are formed. When an external force of a predetermined magnitude or greater is applied to the connecting portions 10 so as to bring the upper edge portion 11 and the lower edge portion 13 closer together, the connecting portions 10 buckle, suppressing an increase in the reaction force (see, for example, FIG. 11 ). In other words, when the battery cushioning material 100 is subjected to an external force (an external force in a direction that brings the upper edge portion 11 and the lower edge portion 13 closer together), the connecting portions 10 deform so as to be crushed, and a reaction force against the external force is generated primarily by the connecting portions 10. When the external force further increases and exceeds a certain level, the connecting portions 10 buckle. This buckling prevents an increase in the reaction force, i.e., maintains the reaction force at a predetermined level (i.e., the degree of increase in the reaction force is gradual even when the compression amount increases, and the plateau (flat) region of the reaction force becomes wider). The external force equal to or greater than a predetermined value refers to an external force equal to or greater than a predetermined value that is set in advance, and the range of load that will be applied to the buffer material due to the thermal expansion of the battery 200 can be estimated in advance, and the timing at which the connecting part 10 should buckle can be set in advance. Furthermore, external impact forces on the battery 200 can also be estimated and set in advance.

There are no particular restrictions on the shape of the connecting part 10, but it can be column-shaped, wall-shaped, etc.

The connecting portion 10 may be a continuous wall extending from one end of the battery cushioning material 100 to the other, or it may be discontinuous (a series of pillar- or wall-shaped portions spaced apart).

"Buckling" means deformation in a bending manner.

There is no particular limit to the number of connecting portions 10, as long as multiple connecting portions 10 are formed. The number can be set appropriately taking into account factors such as the magnitude of the reaction force maintained after buckling.

The connecting portion 10 is preferably formed integrally with the upper edge portion 11 and the lower edge portion 13, but may also be provided as a separate body and joined to the upper edge portion 11 and the lower edge portion 13.

The thickness of the connecting portion 10 can be, for example, approximately 0.5 to 10 mm.

The thickness of the connecting portion 10 may or may not be constant, as long as the connecting portion 10 buckles and suppresses an increase in the reaction force when an external force of a predetermined magnitude or greater is applied so that the upper edge portion 11 and the lower edge portion 13 approach each other. If the thickness is not constant, the thickness may protrude so that the center is thicker than the other portions, as shown in Figure 4 (i.e., a rib 15 may be attached to the center).

The rib 15 may be attached to one surface of the connecting portion 10, or to both surfaces.

Figure 1 shows a battery cushioning material 100 having a connecting portion 10 with a non-uniform thickness, with a rib 15 attached to the center. In other words, this shows an example in which a protrusion is formed so that the center of the connecting portion 10 is thicker than the other portions. By attaching a rib 15 to the center in this way, a strong spring effect is exerted after buckling, further suppressing the decrease in surface pressure, and further flattening the fluctuations in reaction force, resulting in a wider plateau (flat) region (see Figure 11).

Figure 6 shows a battery cushioning material 101 having a connecting portion 10 with a constant thickness. A constant thickness in the connecting portion 10 reduces the amount of strain and stress generated, improving resistance to cracking and other damage. The battery cushioning material 102 shown in Figure 6 has a base portion 20 in which one surface 20a is flat and the other surface 20b is curved.

It is preferable that the thickness of the base of the connecting portion be non-uniform. Specifically, it is preferable that one surface of the base of the connecting portion is curved and the other surface is flat, or that one and the other surfaces of the base be curved and have different radii of curvature. If one surface of the base of the connecting portion is curved and the other surface is flat, it is preferable that this flat surface (with a radius of curvature of 0) be located on the outer side. Furthermore, if the curved surfaces have different radii of curvature, it is preferable that the surface located on the outer side has a smaller radius of curvature. There are no particular restrictions on the size of the radius of curvature of the curved surfaces and they can be set as appropriate.

In this way, when an external force of a predetermined magnitude or greater is applied so that the upper edge portion 11 and the lower edge portion 13 are brought closer together, the connecting portion 10 buckles more reliably. Furthermore, the direction in which the connecting portion 10 buckles can be controlled, preventing adjacent connecting portions 10 from coming into contact with each other. The reason the buckling direction of the connecting portion can be controlled is that by making the internal stress uneven on the left and right sides (one side and the other side) (i.e., the side with the larger radius of curvature has higher internal stress), buckling in the direction of smaller stress becomes more likely.

More specifically, as shown in Figure 6, the connecting portion 10 can have a curved surface 20b at its base 20, which is located toward the center of the battery cushioning material (i.e., toward the center in the direction perpendicular to the thickness direction of the battery cushioning material), and a flat surface 20a (with a radius of curvature of 0) opposite surface 20b. In this case, the connecting portion 10 buckles toward surface 20a (the flat surface), which is the direction in which stress is smaller.

Also, as shown in Figure 7, the battery cushioning material 103 can have both surfaces 20a, 20b of the base portion 20 as curved surfaces A and B, respectively, with the radii of curvature of these curved surfaces A and B being different, with the outer surface 20a (curved surface B) having a smaller radius of curvature. In this case, the connecting portion 10 buckles toward surface 20a (curved surface B), which is the direction of the smaller stress.

The connecting portion 10 may have a thickness that decreases from the center toward the ends (i.e., toward the upper edge 11 and the lower edge 13) of the battery cushioning material 100 in the thickness direction, and the thickness may be asymmetric. This allows for easier buckling at the thinner end (i.e., the end where the thickness is reduced more), thereby controlling the buckling direction of the connecting portion 10. This is because internal stress is uneven between the left and right sides (one side and the other side). Note that "asymmetric thickness" means that the difference between the lengths D1 and D2 of the following perpendicular lines is not zero. That is, when the battery cushioning material is viewed from the side (see, for example, Figure 8), a center line L is drawn that passes through the center O of the connecting portion 10 and is parallel to the thickness direction of the battery cushioning material. Imagine perpendicular lines extending from each of the one surface 20a and the other surface 20b to the center line L, and define the lengths of these perpendicular lines as "lengths D1 and D2 of the perpendicular lines." Furthermore, if the difference between the lengths D1 and D2 of the perpendicular lines extending from the foot of the same perpendicular line to both surfaces 20a and 20b is not zero, it is said that the thickness is asymmetric. In other words, if the difference between the lengths D1 and D2 of the perpendicular lines is zero, it can be said that the connecting portion 10 is uniformly (i.e., symmetrically) thin.

The connecting portion 10 can be formed from a pair of connecting bodies 30, 30, as in the battery cushioning material 102 shown in Figure 9. Each of the pair of connecting bodies 30, 30 is provided with a rib 15. Note that Figure 9 shows the battery cushioning material 102 in a state where no external force is being applied.

Figure 10 shows a state in which the connecting portion 10 of a battery cushioning material 102, which has a connecting portion 10 formed from a pair of connecting bodies 30, 30, is buckled. In Figure 10, an external force of a predetermined magnitude or greater is being applied so that the upper edge portion 11 and the lower edge portion 13 are brought closer together. The pair of connecting bodies 30, 30 are buckled in different directions (buckled away from each other) so as not to collide with each other.

The pair of connecting bodies 30, 30 may be in contact with each other or may be spaced apart.

The position where the connecting portion 10 is formed is not particularly limited and can be set as appropriate.

The material for the connecting portion 10 can be selected from conventionally known rubber materials, but specific examples include ethylene propylene diene rubber (EPDM) and acrylic rubber (ACM).

There are no particular restrictions on the hardness of the connecting portion 10, but the value measured using JIS K 6253 Durometer Type A can be between 10 and 90 degrees, and preferably between 40 and 90. By keeping the hardness within this range, when an external force greater than a predetermined level is applied so that the upper edge portion 11 and the lower edge portion 13 are brought closer together, the connecting portion 10 buckles, effectively suppressing an increase in the reaction force.

(1-2) Top part:
The upper edge portion 11 is a plate-shaped portion that comes into contact with one of the members that applies an external force to the battery cushioning material 100. For example, as shown in FIG. 1 , when the battery cushioning material 100 is placed between two battery cells 210, the upper edge portion 11 comes into contact with one of the battery cells 210.

This upper edge portion 11 may be flat, curved, or wavy. There are no particular restrictions on the thickness of the upper edge portion 11 and it can be set as appropriate, for example, approximately 0.3 to 5 mm.

The material for the upper edge portion 11 is not particularly limited, but examples include rubber and resin. It is preferable to use the same rubber material as the connecting portion 10, and it can be formed integrally with the connecting portion 10.

(1-3) Bottom part:
The lower edge portion 13 is a plate-shaped portion that comes into contact with another member that applies an external force to the battery cushioning material 100. For example, as shown in Fig. 1 , when the battery cushioning material 100 is placed between two battery cells 210, the lower edge portion 13 comes into contact with the other battery cell 210 (the side opposite to the upper edge portion 11).

This bottom edge portion 13 may be flat, curved, or wavy. There are no particular restrictions on the thickness of the bottom edge portion 13 and it can be set as appropriate, for example, approximately 0.3 to 5 mm.

The material of the lower edge portion 13 is not particularly limited, but examples include rubber and resin. It is preferable to use the same rubber material as the connecting portion 10, and it can be formed integrally with the connecting portion 10.

(2) Use of the battery cushioning material of the present invention:
The battery cushioning material 100 can be disposed between adjacent battery cells 210 as in the battery 200 shown in FIG. 1 , or between a stack of multiple battery cells 210 and a restraining portion 230 as in the battery 201 shown in FIG. 2 . It should be noted that the battery cushioning material 100 is not limited to one, and multiple materials can also be used. In this case, multiple battery cushioning materials 100 may be stacked or may be arranged on a plane, or these may be combined. The battery is not limited to an all-solid-state battery, and may also be a liquid electrolyte battery.

By arranging it in this way, it can absorb the expansion force that occurs when the battery cell (battery) expands and function as a buffer when the battery is subjected to an external impact. Furthermore, it can absorb and correct pressure imbalances caused by variations (placement errors) when stacking components such as the battery cells 210.

Specifically, when the battery 200 thermally expands, the battery cushioning material 100 deforms so that the upper edge 11 and lower edge 13 move closer to each other, absorbing the external force. At this time, a reaction force is generated from the battery cushioning material 100, maintaining a balance with the external force. Thereafter, when the external force exceeds a predetermined level, that is, when the amount of compression reaches a predetermined value, the connecting portion 10 buckles. The buckled connecting portion 10 then generates a reaction force like a spring, and the reaction force is suppressed from increasing even if the amount of compression increases until the predetermined amount of compression is reached.

(Analysis result 1)
Assuming a flat battery cushioning material as shown in Figure 3, a simulation was conducted to analyze the compression amount (mm) and reaction force (N). The material analyzed was EPDM rubber (hardness A90), and the top and bottom surfaces were compressed under rigid wall bonding conditions to generate a reaction force. The analysis results are shown in Figure 11.

As shown in Figure 11, in the case of flat battery cushioning materials such as those shown in Figure 3, the reaction force increases as the amount of compression increases, but once a certain amount of compression is reached, the increase in reaction force is suppressed. In other words, it can be seen that the increase in reaction force is suppressed within a certain range of the amount of compression.

(Analysis result 2)
Assuming a flat battery cushioning material as shown in Figure 6, a simulation analysis was performed on the compression amount (mm) and reaction force (N). The analysis materials and analysis conditions were the same as those in Analysis Result 1. The analysis results are shown in Figure 12.

As shown in Figure 12, a temporary fluctuation in reaction force was observed when the flat battery cushioning material shown in Figure 6 buckled at the connection point. However, other than this, as in Analysis Result 1, it can be seen that the increase in reaction force is suppressed within a specified range of compression.

(Reference example 1)
Fig. 13 shows the relationship between the amount of compression (mm) and the reaction force (N) in a conventional battery cushioning material such as the battery cushioning material 300 shown in Fig. 14. As shown in Fig. 13, as the amount of compression of the battery cushioning material increases, the increase in reaction force becomes much larger compared to the increase in the amount of compression.

As can be seen from the above-mentioned Analysis Results 1 and 2 and Reference Example 1, the battery cushioning material of the present invention suppresses an increase in reaction force even when subjected to a large external force, as long as the compression amount is within a specified range. Therefore, even if the battery thermally expands or an external impact is applied, causing the cushioning material to be significantly compressed, as long as the compression amount is within a specified range, the increase in the reaction force generated is suppressed, making it difficult for a large reaction force to occur. As a result, it is possible to avoid damage to the battery caused by the reaction force generated by the battery cushioning material.

The battery cushioning material of the present invention can be used as a cushioning material for batteries such as lithium batteries used in electric vehicles, etc.

10: Connecting portion 11: Upper side portion 13: Lower side portion 15: Rib 20: Base portion 20a, 20b: Surface 30: Connecting body 100, 101, 102, 103, 104, 300: Battery cushioning material 200, 201: Battery 210: Battery cell 230: Restraining portion D1, D2: Length of perpendicular line L: Center line O: Center

Claims (5)

The device has an upper side portion, a lower side portion, and a plurality of connecting portions connecting the upper side portion and the lower side portion,
the connecting portion is made of an elastic material,
the connecting portion has one surface at its base portion that is curved and the other surface that is flat, or one surface and the other surface at the base portion that are curved and have different radii of curvature;
When an external force of a predetermined magnitude or greater is applied so that the upper edge portion and the lower edge portion approach each other, the connecting portion buckles, thereby suppressing an increase in the reaction force. When one surface of the connecting portion at its base portion is curved and the other surface is flat, the flat surface is located on the outer side,
The cushioning material for a battery according to claim 1 , wherein when the curved surfaces have different radii of curvature, the surface located on the outer side has a smaller radius of curvature. The cushioning material for a battery according to claim 1 or 2 , wherein the connecting portion is formed by a pair of connecting bodies. The cushioning material for a battery according to any one of claims 1 to 3 , wherein the connecting portion has a rib attached to the center thereof. The device has an upper side portion, a lower side portion, and a plurality of connecting portions connecting the upper side portion and the lower side portion,
the connecting portion is made of an elastic material,
The connecting portion has a rib attached to the center thereof,
When an external force of a predetermined magnitude or greater is applied so that the upper edge portion and the lower edge portion approach each other, the connecting portion buckles, thereby suppressing an increase in the reaction force.