JP7793458B2 - Battery cushioning material - Google Patents

Description

The present invention relates to a cushioning material for batteries, and more particularly to a cushioning material for batteries such as secondary batteries used in electric vehicles and the like.

Battery cushioning materials are conventionally known that are placed between two opposing flat rigid bodies to elastically alleviate the compressive force between the two rigid bodies. For example, in batteries (secondary batteries) used in electric vehicles, etc., a typical example is battery cushioning placed between the multiple battery cells that make up the battery, or between a stack of multiple battery cells and a housing (restraint) that holds them in place (see, for example, Patent Document 1). By placing such battery cushioning material between the rigid bodies, it is possible to alleviate excessive compressive force while ensuring the compressive force necessary to maintain the integrity of the entire battery, including the rigid bodies.

Japanese Patent Application Laid-Open No. 2020-4556

Generally, battery cushioning materials can absorb sufficient displacement while maintaining a high reaction force (surface pressure) when they are initially subjected to compressive force between rigid bodies after being placed between them. However, once the compressive force is released, so-called hysteresis loss makes it difficult for the material to exert sufficient reaction force. While it is possible to make the battery cushioning material denser in advance so that it can exert sufficient reaction force after the load is released, this reduces the amount of displacement that can be absorbed. For this reason, further ingenuity is required to maintain sufficient reaction force while fully absorbing displacement.

In consideration of the above circumstances, the present invention aims to create a cushioning material for batteries that is suitable for adequately absorbing displacement while maintaining sufficient reaction force.

To solve the above-mentioned problems, the present invention provides the following battery cushioning material.

[1] A cushioning material for a battery that is interposed between two flat rigid bodies facing each other and elastically relieves a compressive force between the two rigid bodies, the cushioning material comprising: a plurality of abutting portions each having an opposing surface that faces one of the two rigid bodies, the opposing surface having a U-shaped recessed shape in a cross section along the thickness direction of the cushioning material before receiving the compressive force, and abutting against one of the rigid bodies along the surface of the one of the rigid bodies when receiving the compressive force; and a plurality of support portions that connect the abutting portion of the plurality of abutting portions that abut against one of the two rigid bodies and the abutting portion of the plurality of abutting portions that abut against the other of the two rigid bodies, the support portions being deformed into an S-shaped curved shape in the cross section when receiving the compressive force,
The battery cushioning material has a configuration in the cross section consisting of a series of M-shapes, with the multiple abutment portions and the multiple support portions being alternately connected, and two adjacent support portions among the multiple support portions form a hollow space between the two support portions before being subjected to the compressive force, and when subjected to the compressive force, the two support portions deform in such a manner that the bent portions of the two support portions, which are curved in an S shape, are accommodated in the hollow space, thereby crushing the hollow space and reducing the thickness of the battery cushioning material.

[2] The battery cushioning material described in [1], wherein the two support pillars form a hollow space that is approximately V-shaped in cross section.

[3] The battery cushioning material described in [1] or [2], wherein the plurality of support pillars have flat surfaces represented by straight lines in the cross section before being subjected to compressive forces from the two rigid bodies.

[4] The battery cushioning material described in [1] or [2], wherein the plurality of support pillars have an uneven surface in the cross section represented by repeated concaves and convexes before being subjected to compressive forces from the two rigid bodies.

In this invention, the support section bends in an S-shape when subjected to compressive force from two rigid bodies, and the bent section is housed in the hollow space between two adjacent support sections, allowing for sufficient absorption of displacement. Furthermore, even after the compressive force is released, compressive stress tends to remain in the bent section, allowing for sufficient reaction force to be maintained. As a result, this invention achieves a battery cushioning material that is suitable for adequately absorbing displacement while maintaining sufficient reaction force.

1 is a cross-sectional view schematically illustrating a state in which a cushioning material for a battery according to one embodiment of the present invention is used. 1. FIG. 4 is a cross-sectional view schematically showing another state of use of the battery cushioning material of FIG. FIG. 3 is a perspective view of the battery cushioning material of FIGS. 1 and 2 . 4 is a cross-sectional view of the battery cushioning material of FIG. 3 before it receives a compressive force from two rigid bodies. FIG. 5 is a cross-sectional view of the battery cushioning material of FIG. 4 when it is subjected to a compressive force from two rigid bodies. 6 is a cross-sectional view of the battery cushioning material of FIG. 4 when it is subjected to a compressive force from two rigid bodies that is greater than that in the state of FIG. 5 . FIG. 7 is a diagram showing the distribution of compressive stress remaining in the battery cushioning materials of FIGS. 3 to 6 after the compressive load is released. FIG. 7 is a graph showing the change in reaction force with respect to the amount of compression for one specific example of the battery cushioning material of FIGS. 3 to 6. 10 is a cross-sectional view along the thickness direction of a portion of another embodiment of a cushioning material for a battery according to the present invention, in which a plurality of support posts have non-flat surfaces. FIG.

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.

The battery cushioning material of this embodiment is a battery cushioning material that is interposed between two opposing flat rigid bodies to elastically relieve the compressive force between the rigid bodies, and is made of an elastic material (typically rubber or elastomer).

Figure 1 is a cross-sectional view showing a battery cushioning material 1 according to one embodiment of the present invention in use, and Figure 2 is a cross-sectional view showing another use state of the battery cushioning material 1 shown in Figure 1.

The battery cushioning material 1 of this embodiment can be placed between adjacent battery cells 210, as in the battery 200 shown in FIG. 1, or between a stack 220 consisting of multiple battery cells 210 and a restraining portion 230, as in the battery 201 shown in FIG. 2. It should be noted that multiple battery cushioning materials 1 can be used, not just one. In this case, multiple battery cushioning materials 1 can be stacked and used, or multiple materials can be arranged on a flat surface, or these can be combined. The battery is not limited to an all-solid-state battery, and can also be a liquid electrolyte battery.

Figure 3 is a perspective view of the battery cushioning material 1 of Figures 1 and 2, Figure 4 is a cross-sectional view of the battery cushioning material 1 of Figure 3 before it receives a compressive force from two rigid bodies, Figure 5 is a cross-sectional view of the battery cushioning material 1 of Figure 4 when it receives a compressive force from two rigid bodies 10, 20, and Figure 6 is a cross-sectional view of the battery cushioning material 1 of Figure 4 when it receives a compressive force from two rigid bodies 10, 20 that is greater than that in the state of Figure 5.

Battery cushioning material 1 extends continuously in the horizontal direction (left-right direction) in each of Figures 3 to 6, and only a portion of it is shown in Figures 3 to 6. Here, the phrase "a state before being subjected to a compressive force from two rigid bodies" in this application refers to a state in which battery cushioning material 1 has never been interposed between two rigid bodies 10, 20 and the shape of the single battery cushioning material 1 at the time of manufacture is maintained as is, i.e., the state before it is used as a battery cushioning material. Furthermore, rigid bodies 10, 20 can be, for example, battery cells that make up a battery (secondary battery) used in electric vehicles, or a housing (more precisely, the housing wall) that holds such a stack of battery cells by sandwiching them. In this case, battery cushioning material 1 functions as a battery cushioning material placed between battery cells or between the stack of battery cells and the housing.

As shown in Figure 4, the battery cushioning material 1 has, as its constituent parts, multiple contact portions 2 and multiple support portions 3.

Each of the multiple abutment portions 2 has an opposing surface 2a that faces the upper rigid body 10 or the lower rigid body 20 in Figure 4. As shown in Figure 4, the opposing surface 2a has a U-shaped recessed shape in a cross section along the thickness direction of the battery cushioning material 1 before it receives a compressive force from the rigid bodies 10, 20. Because of this U-shaped recessed shape, when it receives a compressive force from the rigid bodies 10, 20, the opposing surface 2a comes into tight contact with and adheres to the rigid bodies 10, 20 along their surfaces, as shown in Figures 5 and 6. As a result, the compressed state of the battery cushioning material 1 is stabilized.

As shown in Figure 4, the multiple support columns 3 are sections that connect the contact section 2 that contacts the upper rigid body 10 in Figure 4 with the contact section 2 that contacts the lower rigid body 20 in Figure 4. As shown in Figures 5 and 6, the multiple support columns 3 are deformed into an S-shaped curve when subjected to compressive forces from the rigid bodies 10 and 20. The degree of curvature here depends on the compressive forces from the rigid bodies 10 and 20, and the greater the compressive force, the greater the degree of curvature. For example, in Figure 5, the degree of S-shaped curvature is slight, but in Figure 6, the degree of S-shaped curvature is extremely large.

As shown in Figure 4, these multiple abutment portions 2 and multiple support portions 3 are alternately connected in the left-right direction of Figure 4, resulting in the battery cushioning material 1 having a continuous M-shaped configuration.

Here, two adjacent support columns 3 among the multiple support columns form a hollow space S between them, as shown in Figure 4, before they are subjected to compressive force from the rigid bodies 10, 20. Then, as shown in Figures 5 and 6 (particularly Figure 6), upon receiving compressive force from the rigid bodies 10, 20, the two support columns 3 are deformed such that the bent portions 3a of the two S-shaped support columns 3 are housed in the hollow space S. This deformation collapses the hollow space S, reducing the thickness of the battery cushioning material 1.

In battery cushioning material 1, the support section 3 bends in an S-shape when subjected to compressive force from the two rigid bodies 10, 20, and the bent section is accommodated in the hollow space S between two adjacent support sections 3, allowing for sufficient absorption of displacement. Furthermore, even after the compressive force is released, compressive stress tends to remain in the bent section, allowing sufficient reaction force to be maintained. As a result, battery cushioning material 1 is suitable for adequately absorbing displacement while maintaining sufficient reaction force.

Figure 7 shows the distribution of compressive stress remaining in the battery cushioning material 1 of Figures 3 to 6 after the compressive load is released.

As shown in Figure 7, compressive stress tends to remain in the S-shaped curved bent portion of the support column 3, particularly near the bent inner surface 3b. By providing the battery cushioning material 1 shown in Figure 4 with a shape that creates such an inner surface 3b, sufficient reaction force can be maintained even after the compressive load is released.

Figure 8 is a graph showing the change in reaction force versus compression amount for one specific example of the battery cushioning material 1 shown in Figures 3 to 6. For reference, Figure 8 also includes a graph showing the change in reaction force versus compression amount for a conventional battery cushioning material made of flat foam.

Figure 8 shows graph A1 of the change in reaction force versus the amount of compression when a compressive force is applied for the first time for one specific example of battery cushioning material 1, and graph A2 of the change in reaction force versus the amount of compression when a second compressive force is applied after the first load is released. Also shown are graphs B1 and B2 of the change in reaction force versus the amount of compression when a conventional battery cushioning material is applied for the first time for one specific example of battery cushioning material 1, and graph B2 of the change in reaction force versus the amount of compression when a second compressive force is applied after the first load is released.

When conventional battery cushioning materials are subjected to an initial compressive load, they are able to absorb a sufficient amount of compression (displacement) while maintaining a relatively high reaction force (surface pressure), as shown in graph B1 of Figure 8. However, when the first compressive load is released and a second compressive load is applied, they are unable to exert sufficient reaction force unless they are significantly compressed, as shown in graph B2 of Figure 8 (this is known as hysteresis loss).

On the other hand, in one specific example of battery cushioning material 1, when a compressive force is applied for the first time, it is able to absorb a sufficient amount of compression (displacement) while maintaining a relatively high reaction force (surface pressure) compared to conventional battery cushioning materials, as shown in graph A1 of Figure 8. Furthermore, when a second compressive force is applied after the first compressive force is released, it is able to exert a sufficient reaction force without being compressed as much as conventional battery cushioning materials, as shown in graph A2 of Figure 8.

In this way, one specific example of this battery cushioning material 1 is a battery cushioning material that is suitable for adequately absorbing displacement while maintaining sufficient reaction force, compared to conventional battery cushioning materials made of flat foam.

Graph A2 in Figure 8 shows a plateau region P where the reaction force remains nearly constant even as the amount of compression increases. This corresponds to the state in which the bent portions 3a of the two S-shaped support posts 3 begin to occupy the hollow space S, as shown in Figure 6. In this state, a high reaction force is maintained even as the amount of compression increases, and the reaction force does not change significantly until the hollow space S completely disappears. The presence of this plateau region P prevents a sudden increase in the reaction force in response to volumetric compression (thickness reduction) of the battery cushioning material 1. The reaction force in the plateau region P can be adjusted to the desired magnitude by adjusting the thickness and shape of the battery cushioning material 1 in its initial state before compression (for example, the angle between the support posts 3 and the abutting portions 2), the Young's modulus of the material, etc.

Let's return to Figures 3 to 6 to continue the explanation.

In the present invention, as shown in Figure 4, a configuration in which two support pillars 3 form a hollow space S in an approximately V shape is preferred. Here, "approximately V-shaped" refers to a shape that is close to a V, and includes not only a V-shape itself, but also a shape in which the width narrows as it approaches the bottom, such as a shape with a rounded bottom that is close to a U-shape.

By forming a roughly V-shaped hollow space S with the two support sections 3 in this way, the bent portions 3a of the two S-shaped support sections 3 can be smoothly accommodated in the hollow space S, preventing abrupt changes in the reaction force in response to changes in the amount of compression.

Furthermore, in the present invention, as shown in Figure 4, before the battery cushioning material 1 is subjected to compressive forces from the two rigid bodies 10, 20, it is preferable that the multiple support pillars 3 have flat surfaces represented by straight lines in the cross-sectional view.

In this configuration, the shape of the multiple support pillars 3 is simple, making it easy to manufacture the battery cushioning material 1.

However, in the present invention, before the battery cushioning material is subjected to a compressive force, the multiple support posts may have an uneven surface, as represented by repeated projections and depressions in a cross-sectional view. Below, we will explain an embodiment of this type of battery cushioning material, which is different from the battery cushioning material 1 shown in Figures 3 to 6.

Figure 9 is a cross-sectional view along the thickness direction of a portion of a battery cushioning material 1' in another embodiment of the present invention, in which multiple support posts 3' have non-flat surfaces.

In Figure 9, the same components as those in the battery cushioning material 1 in Figures 3 to 6 are designated by the same reference numerals, and redundant explanations will be omitted. The battery cushioning material 1' in Figure 9 differs from the battery cushioning material 1 in Figures 3 to 6 in that, before being subjected to a compressive force, it has multiple support posts 3' with uneven surfaces, as represented by repeated projections and depressions in the cross-sectional view of Figure 9; apart from this, it is the same as the battery cushioning material 1 in Figures 3 to 6.

Compared to the battery cushioning material 1 shown in Figures 3 to 6, this type of battery cushioning material 1' is at a disadvantage in terms of ease of manufacturing the battery cushioning material 1 due to the complex shape of the multiple support pillars 3. However, compared to the support pillars 3 of the battery cushioning material 1 shown in Figures 3 to 6, the support pillars 3' of the battery cushioning material 1' are more prone to bending and deformation, making internal strain less likely to occur in the battery cushioning material 1'. This makes it advantageous in terms of preventing internal strain.

The above is a description of an embodiment of the present invention.

The above explanation has been about one sheet of battery cushioning material sandwiched between two rigid bodies, but the present invention may also be applied to a stack of multiple pairs of two rigid bodies and one sheet of battery cushioning material.

The present invention is useful for creating a cushioning material for batteries that is suitable for adequately absorbing displacement while maintaining sufficient reaction force.

1, 1': cushioning material for batteries,
2: Contact part,
2a: Opposing surface,
3, 3': Support part,
3a: bent part,
3b: inner surface,
10, 20: Rigid body,
200, 201: Battery,
210: battery cell,
220: laminate,
230: Restraint part,
A1, A2, B1, B2: graph,
P: plateau region,
S: Hollow space.

Claims (4)

A battery cushioning material that is interposed between two opposing flat rigid bodies to elastically relieve the compressive force between the two rigid bodies,
a plurality of contact portions each having an opposing surface that faces one of the two rigid bodies, the opposing surface having a U-shaped recess in a cross section along a thickness direction of the battery cushioning material before receiving the compressive force, and that abuts against the one of the rigid bodies along a surface of the one of the rigid bodies when receiving the compressive force;
a plurality of support columns that connect a contact portion of the plurality of contact portions that contacts one of the two rigid bodies with a contact portion of the plurality of contact portions that contacts the other of the two rigid bodies, and that deform into an S-shaped curved shape in the cross section when subjected to the compressive force;
the battery cushioning material has a configuration in which the plurality of contact portions and the plurality of support portions are alternately connected to form a continuous M-shape in the cross section,
Before being subjected to the compressive force, two adjacent support pillars among the plurality of support pillars form a hollow space between the two support pillars, and when subjected to the compressive force, the two support pillars deform in such a manner that the bent portions of the two support pillars, which are curved in an S-shape, are accommodated in the hollow space, thereby crushing the hollow space and reducing the thickness of the battery cushioning material. The battery cushioning material according to claim 1, wherein the two support pillars form a hollow space that is approximately V-shaped in cross section. The battery cushioning material described in claim 1 or 2, wherein the plurality of support pillars have flat surfaces represented by straight lines in the cross section before being subjected to compressive forces from the two rigid bodies. The battery cushioning material described in claim 1 or 2, wherein the multiple support pillars have an uneven surface represented by repeated concaves and convexes in the cross section before being subjected to compressive forces from the two rigid bodies.