JP7725607B2 - Elastic body for battery module - Google Patents

Description

The present invention relates to an elastic body for a battery module.

In secondary batteries, such as lithium-ion secondary batteries, the degree of expansion and contraction of battery cells during charging and discharging has increased in recent years due to improvements in charge and discharge capacity. Furthermore, secondary battery modules used in automobiles and other applications require higher energy density (smaller battery size) to improve fuel efficiency. In such secondary battery modules, multiple battery cells are densely stacked, and as the battery cells expand during charging, adjacent battery cells may press against each other, potentially damaging the battery cells. Therefore, elastic bodies (battery module elastic bodies) are provided as cushioning between the battery cells and between the battery cells and components that restrain the stacked battery cell structure. For example, Patent Document 1 describes a buffer sheet for battery modules that has a plate-shaped base and elastic convex portions with a predetermined inclination. The sheet elastically supports the battery cells when they expand in a curved, convex manner during charging, and applies a reaction force to the battery cells when they contract during discharging.

Japanese Patent Application Laid-Open No. 2020-004556

The reaction force of an elastic body is usually small when compressed lightly and large when compressed heavily. On the other hand, the above-mentioned elastic body for a battery module is required to exhibit a load-displacement characteristic such that the surface pressure (reaction force) at the portion that comes into contact with the battery cells, etc., is not too low when compressed lightly, and not too high when compressed heavily. This load-displacement characteristic allows the elastic body to sufficiently repel relatively low restraint loads, such as those applied during assembly in battery module manufacturing or during battery module discharge, contributing to the stable maintenance of the stacked structure of the battery module, while also being able to sufficiently absorb restraint loads during battery cell charging so as to avoid high restraint loads (battery cell allowable limit loads) that would cause battery cell damage.
To achieve the above load-displacement characteristics, it is possible to consider optimizing the materials, such as the elastomer material that constitutes the elastic body. However, the variety of elastomer materials available on the market is limited, and considering the cost, there are many restrictions on improving the load-displacement characteristics through material selection.
Therefore, an object of the present invention is to achieve the load-displacement characteristics required of the elastic body for a battery module by mainly controlling the shape of the elastic body.

In light of the above-mentioned problems, the inventors conducted extensive research and found that by configuring an elastic body with a base material and multiple protrusions protruding from both sides of the base material, and by arranging the protrusions on both sides of the base material in a specific, regular pattern, sufficient reaction force can be generated from the top surfaces of the protrusions when the elastic body is lightly compressed, while effectively suppressing the reaction force when the elastic body is heavily compressed. The present invention was completed after further research based on these findings.

That is, the above-mentioned problems of the present invention have been solved by the following means.
[1]
An elastic body for a battery module that is disposed between adjacent battery cells and/or between a battery cell and a restraining member of a battery module including a plurality of battery cells and a restraining member,
The elastic body for a battery module has a base portion and a plurality of convex portions protruding from the base portion, and when the elastic body is viewed in a plane, is composed of an inner region in which the plurality of convex portions have the following regular arrangement, and an outer region other than the inner region.
[Regular array]
When the elastic body is viewed in a plane:
a plurality of first protrusions arranged at equal intervals in the longitudinal direction of the elastic body;
a plurality of second protrusions arranged at equal intervals in the longitudinal direction of the elastic body and positioned at four corners of a rectangle having the first protrusion at its center;
A repeating array consisting of.
[2]
The elastic body for a battery module according to [1], wherein the heights of the plurality of first convex portions and the plurality of second convex portions protruding from the base portion are the same height from the surface of the base portion.
[3]
The height of the plurality of first convex portions and the second convex portions protruding from the base material portion increases from the center side toward the outer periphery side of the base material portion.
[4]
The elastic body for a battery module according to any one of [1] to [3], wherein the first convex portions and the second convex portions are cylindrical, and when the regular arrangement is viewed in a plan view, a shortest distance x (mm) from the center of the first convex portion to the center of the second convex portion and a diameter y (mm) of the first convex portion satisfy the following formulas (1) to (3):
y<7/8x+1/2 (1)
y>3/8x+3/8 (2)
x>6 (3)
[5]
The elastic body for a battery module according to [4], wherein the diameter y (mm) satisfies the following formula (4):
4≦y≦14 (4)
[6]
The elastic body for a battery module according to [1], wherein the outer region is formed so as to surround the entire periphery of the inner region when the elastic body is seen in a plan view.
[7]
The elastic body for a battery module according to [1] or [6], wherein the density of the convex portions in the outer region is lower than the density of the convex portions in the inner region.

The elastic body for battery modules of the present invention achieves the above-mentioned load-displacement characteristics required of elastic bodies for battery modules from the perspective of shape control of the elastic body. The elastic body for battery modules of the present invention makes it possible to create elastic bodies that exhibit superior load-displacement characteristics in accordance with various specifications of battery modules, for example, by combining the selection of the constituent materials of the elastic body with shape control of the elastic body.

1 is a plan view showing an embodiment of an elastic body for a battery module of the present invention. 1 is a cross-sectional view showing one embodiment of an elastic body for a battery module of the present invention. FIG. 2 is an enlarged plan view showing a portion of the inner region. 4A and 4B are explanatory diagrams schematically illustrating an embodiment of a battery module to which the elastic body for a battery module of the present invention is applied, in which Fig. 4A shows the battery module in a state in which the battery cells are not expanded, and Fig. 4B shows the battery module in a state in which the battery cells are fully expanded when fully charged. 1 is a plan view showing an example of the configuration of an elastic body according to an embodiment of the present invention. 1 is a plan view showing an example of the configuration of an elastic body according to an embodiment of the present invention. 1 is a plan view showing an example of the configuration of an elastic body according to an embodiment of the present invention. 1 is a plan view showing an example of the configuration of an elastic body according to an embodiment of the present invention. FIG. 10 is a plan view showing an example of the configuration of an elastic body according to a comparative example of the present invention. 10 is a graph plotting the diameters and center distances of the convex portions of the elastic bodies according to the comparative example and the example. 1 is a graph showing load-displacement characteristics of elastic bodies according to examples of the present invention and comparative examples. 1 is a graph showing load-displacement characteristics of an elastic body according to an example of the present invention. 1 is a cross-sectional view showing an example of the configuration of an elastic body according to an embodiment of the present invention.

In the present invention and the specification, the term "to" indicating a range of values includes the values written on both sides. For example, when a is a value between b and c, the range of a includes values b and c, and expressed in mathematical notation, b≦a≦c.
In the present invention and the specification, unless otherwise specified, the terms "angle expressed by a specific numerical value,""parallel,""similar,""same," and the like include a generally acceptable error range in the relevant technical field.

The elastic body for a battery module of the present invention is used by being disposed between adjacent battery cells and/or between a battery cell and a restraining member in a battery module formed by holding a stack structure of multiple battery cells with a restraining member.
The following describes an embodiment of an elastic body for a battery module of the present invention, with reference to the accompanying drawings. However, the embodiment described below shows a preferred embodiment of the present invention, and the present invention is not limited to the following except as defined in the present invention.

[Elastic body for battery module]
A preferred embodiment of the elastic body for a battery module of the present invention (hereinafter also referred to as the "elastic body of the present invention") is shown in Figures 1 and 2. The elastic body 1 of the present invention shown in Figures 1 and 2 includes a substrate 2 and a plurality of protrusions 3 arranged on both surfaces (a first surface 2d and a second surface 2h) of the substrate 2.
2, the elastic body 1 of the present invention has a thick portion 2c provided on the outer periphery of the substrate portion 2, a surface 2e parallel to the first surface 2d of the substrate portion 2, including the upper surface 2b of the convex portion, and a space 2g. The first direction and the second direction shown in FIGS. 1 and 2 are two axial directions that are mutually perpendicular and are common to all drawings in this specification. The "dotted lines" in the drawings of this application are used to designate specific convex portions among multiple convex portions, and do not indicate the internal structure.

In the elastic body 1 of the present invention, the base portion and the protrusions may be integrally formed using the same material, or may be formed by bonding the two using different materials. Preferably, they are integrally formed using the same material. If the same material is used, the base portion and the protrusions are preferably formed from an elastomer. If different materials are used, the base portion can be made of a metal plate such as aluminum, iron, or stainless steel, and the protrusions can be made of an elastomer. Furthermore, the elastic body can be formed by two-color molding using different types of elastomers for the base portion and the protrusions. Specifically, the base portion and the protrusions can be made of different types of elastomers, such as polycarbonate (PC) and polyester-based thermoplastic elastomer (TPEE). It is preferable that the elastomer forms a crosslinked structure when the elastic body is constructed. This crosslinked structure can be formed using a crosslinking agent. Examples of crosslinking agents that can be used include organic peroxides and other agents commonly used in the vulcanization of elastomers.

Suitable examples of the elastomer include ethylene propylene diene rubber (EPDM), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), chloroprene rubber (CR), butyl rubber (isobutylene-isoprene rubber) (IIR), etc. Among these, from the viewpoint of compression set (resistance to set), it is preferable that the elastomer be EPDM.
From the viewpoints of providing an appropriate reaction force, preventing cracks, and preventing cracks during the manufacturing process, the rubber hardness of the elastomer constituting the elastic body 1 of the present invention is preferably 54 degrees or more, more preferably 60 degrees or more, and even more preferably 65 degrees or more, in accordance with JIS K6253:2012. From the same viewpoint, the rubber hardness is preferably 82 degrees or less, more preferably 75 degrees or less, and even more preferably 70 degrees or less.
From the same viewpoint as above, the compression set of the elastomer constituting the elastic body 1 of the present invention is preferably 20% or less, more preferably 15% or less, and even more preferably 12% or less, as measured by a compression set test at 150°C for 280 hours in accordance with JIS K6262:2013.
Furthermore, from the same viewpoint as above, the breaking elongation of the elastomer constituting the elastic body 1 of the present invention is preferably 120% or more, more preferably 150% or more, and even more preferably 180% or more, in a tensile test at room temperature (25°C) in accordance with JIS K6251:2017. In this specification, "breaking elongation of 120%" means that the sample breaks when its length is 2.2 times that of the sample before the test.

As shown in FIG. 1, the elastic body 1 of the present invention is symmetrical about a center line L2 (a center line along the longitudinal direction (first direction) of the elastic body) and about a center line L1 (a center line along the lateral direction (second direction) of the elastic body 1). The size of the elastic body 1 of the present invention can be set appropriately taking into consideration the size of the battery module and battery cell to which it is applied. For example, in FIG. 1, the dimension in the first direction of the elastic body 1 of the present invention can be, for example, 100 to 500 mm, preferably 200 to 400 mm, or preferably 250 to 350 mm. The dimension in the second direction of the elastic body 1 of the present invention can be, for example, 50 to 200 mm, preferably 75 to 150 mm, or preferably 80 to 110 mm.

The elastic body 1 of the present invention is disposed between adjacent battery cells of a battery module, or between a battery cell and a restraining member. The elastic body 1 of the present invention can effectively absorb the expansion and deformation that accompanies charging of the battery cell by suppressing the reaction force, and can also provide sufficient reaction force when the battery cell contracts due to discharge, contributing to the stable maintenance of the stacked structure of the battery cells.

Next, each part constituting the elastic body 1 of the present invention will be described.
<Base material part>
As shown in Fig. 2, the substrate 2, which serves as the base of the elastic body 1, is plate-shaped and has a first surface 2d and a second surface 2h. In the embodiment shown in Fig. 1, the first surface 2d and the second surface 2h have an inner region IE in which a plurality of convex portions are arranged in a regular array (described below), and an outer region OE having convex portions surrounding the inner region IE. The inner region IE is the region in which the plurality of convex portions are arranged in a "regular array" (described below). Here, if the convex portions are, for example, truncated cones, the bottom surfaces of the truncated cones of the convex portions contact the surface of the substrate 2.
The ratio of the area of the inner region IE when the elastic body 1 is viewed in plan (the percentage of the area of the inner region IE in plan view relative to the area of the elastic body 1 in plan view) can be, for example, 20 to 98%, preferably 30 to 95%, and more preferably 40 to 90%. Note that although only the first surface 2d side is shown in Fig. 1, the second surface 2h side is usually configured in the same way as the first surface 2d side.
In the present invention, both the inner region and the outer region have convex portions. Furthermore, in the present invention, the outer region does not necessarily have to be disposed around the entire periphery of the inner region, and the outer region may be disposed around only a portion of the periphery of the inner region (e.g., FIGS. 7 and 8).
Incidentally, by making the number of protrusions in the outer region OE smaller than in the inner region IE (i.e., by making the protrusion density (number of protrusions per unit area) smaller), the effect of the inner region IE, which absorbs pressure changes due to expansion and contraction of the battery cell during charging and discharging, is not hindered. In other words, it is preferable that the protrusion density in the outer region OE is smaller than that of the inner region IE. Specifically, as shown in Table 1 below, the protrusion density in the inner region IE is 0.36 to 0.83/ ^cm2 , and the protrusion density in the outer region OE is 0.087 to 0.57/ ^cm2 .

[Convex part]
As shown in FIG. 2, the elastic body 1 of the present invention has a plurality of protrusions 3 formed to protrude from both surfaces (first surface 2d and second surface 2h) of the substrate in the thickness direction of the substrate.
In the present invention, the pressure-receiving area (size) and number of convex portions can be set so that the convex portions can absorb the increase in pressure caused by the expansion of the battery cells during charging, and can also apply a reaction force to the battery cells when the battery cells contract during discharging.
It is not necessary for the protrusions to be present on both sides of the elastic body 1, and it goes without saying that they may be provided on only one side of the elastic body 1 as long as they can absorb the pressure changes that accompany the expansion and contraction of the battery cells.

The shape of the convex portion of the elastic body 1 of the present invention is not particularly limited and may be appropriately designed as long as the effects of the present invention are not impaired. For example, the shape of the convex portion may be a cylindrical shape, a truncated cone shape, a truncated square pyramid shape, or other polygonal truncated pyramid shape. The various truncated cone shapes are shapes in which the cross-sectional area continuously increases from the upper surface of the convex portion toward the substrate portion. Of these, the shape of the convex portion is preferably a cylindrical shape or a truncated cone shape, and more preferably a cylindrical shape. All of the elastic bodies shown in the drawings have cylindrical convex portions.
The maximum diameter of the convex portions can also be set appropriately depending on the desired pressure-receiving area and the number of arranged convex portions. In this specification, the "maximum diameter of the convex portions" means the diameter of the convex portions if they are circular when viewed from above, or the length of the diagonal line if they are rectangular.
When the shape of the convex portion of the elastic body 1 of the present invention is cylindrical, the maximum diameter (φ) of the convex portion can be, for example, 4 to 14 mm, preferably 5 to 12 mm, and also preferably 6 to 10 mm.

In the elastic body 1 of the present invention, the multiple convex portions 3 in the inner region IE are arranged in a "regular arrangement" as described below. It is preferable that the multiple convex portions 3 in the inner region IE are arranged independently in the first direction and also independently in the second direction.

In the present invention, "regular arrangement" means that the multiple convex portions 3 within the inner region IE consist of multiple first convex portions 3a and multiple second convex portions 3b, and that the multiple first convex portions 3a and multiple second convex portions 3b are arranged according to certain rules described below.

(regular arrangement)
In the present invention, the term "regular arrangement" means
When the elastic body is viewed in a plane:
a plurality of first protrusions arranged at equal intervals in the longitudinal direction of the elastic body;
a plurality of second protrusions arranged at equal intervals in the longitudinal direction of the elastic body and positioned at the four corners of a rectangle or square having the first protrusion at its center;
It is a repetition of an array consisting of
The regular arrangement of the convex portions 3 in the inner region IE will be specifically described with reference to FIGS.
As shown in Fig. 1, the multiple first convex portions 3a are arranged at equal intervals in the first direction of the elastic body 1. That is, the multiple first convex portions 3a are arranged in a first convex portion region 3A that is linear along the first direction. The multiple second convex portions 3b are arranged so as to be located at the four corners of a rectangular region E1 that surrounds the first convex portions 3a. That is, the multiple second convex portions 3b are arranged in a second convex portion region 3B that is linear along the first direction.
Here, the distance x (see FIG. 3) between the center of each of the four second protrusions 3b surrounding the first protrusion 3a and the center of the first protrusion 3a is all equal. In this arrangement, as shown in FIGS. 1 and 3, the second protrusions 3b located at the four corners of the rectangular region E1 also serve as the second protrusions 3b of the adjacent region E1 or region E2. Note that the "center of a protrusion" is synonymous with the center of gravity of the top surface of the protrusion in a plan view.
Moreover, "rectangle" means a square, a rectangle, a parallelogram, etc.
1 , region E2 is interposed between two regions E1 aligned in the second direction, but the present invention is not limited to this. That is, multiple regions E1 may be connected in the second direction while sharing two second protrusions 3b aligned in the first direction (see FIGS. 6 and 8 ). In this case, the two second protrusions 3b located at the two vertices of region E1 in the first direction and not in contact with the periphery of the inner region IE in the first direction also serve as two second protrusions 3b in the first direction in another region E1 adjacent to region E1 in the second direction.
In the present invention, the regular arrangement of the inner area IE is achieved by applying the first convex portion and the second convex portion in accordance with the above rule so that the number of areas E1 in the inner area IE is maximized.

3 is an enlarged plan view of a portion of the inner region IE. In the plurality of independent protrusions 3 constituting region E1, the distance _S1 between two adjacent second protrusions 3b in the first direction, the center distance x (mm) which is the shortest distance between the center of the first protrusion 3a and the center of the second protrusion 3b, the distance S2 (mm) between the center of the second protrusion 3b and the center of the first protrusion 3a along the first direction, the distance _t2 (mm) between the center of the second protrusion 3b and the center of the first protrusion 3a along the _second direction, and the distance _t1 (mm) between two adjacent second protrusions 3b in the second direction can be appropriately set taking into account the diameter y (mm) which is the maximum diameter of the first protrusions 3a and the second protrusions 3b and the occupancy rate ρ (protrusion density) of the protrusions relative to the area of the base 2. For example, the distance _S1 can be 6 to 63 mm, preferably 8 to 39 mm, or preferably 12 to 24 mm. The occupancy rate ρ of the convex portions can be calculated, for example, by the following formula (A).
ρ=[number of convex portions)/[area of region E1]
= [1+(1/4)×4]/[S ₁ ×t ₁ ]
= 2/{(2 × S ₂ ) × (2 × t ₂ )}
= 2/{4 × x sinθ × x cosθ}
=1/{2×x ² ×sinθcosθ} (A)
The occupancy rate ρ can be set to 0.08 to 3.21 pieces/cm ² , and is also preferably set to 0.20 to 1.11 pieces/cm ² .

Furthermore, from the viewpoint of ensuring an appropriate reaction force and avoiding contact between the protrusions, it is preferable that the center distance x, the distance _S1 , and the distance _t1 satisfy the following formulas (B) and (C).
x<S ₁ (B)
x<t ₁ (C)
Furthermore, the angle θ formed by the line segment connecting the centers of the second protrusions 3b along the second direction and the line segment connecting the centers of the second protrusions 3b and the first protrusions 3a is preferably 30 to 60°. By setting this angle, the center distance x becomes smaller than the distances _S1 and _t1 , and contact between the protrusions can be more reliably prevented even when the battery cell expands.

The center distance x is appropriately set from the viewpoint of preventing contact between the convex portions and realizing appropriate load characteristics of the elastic body. The diameter y and center distance x of the first convex portion 3a preferably satisfy the following formulas (1) to (3). When the diameter y and center distance x satisfy the following formula (1), contact between the convex portions can be more effectively suppressed when the elastic body is compressed, and excessive reaction force can be more reliably prevented. Furthermore, when the diameter y and center distance x satisfy the following formula (2), the restraining load can be more reliably withstood. Furthermore, when the diameter y satisfies the following formula (3), contact between the convex portions can be more effectively suppressed when the elastic body is compressed, and excessive reaction force can be more reliably prevented.
y<7/8x+1/2 (1)
y>3/8x+3/8 (2)
x>6 (3)

It is also preferable that the elastic body 1 of the present invention satisfies the following formula (1a).
y<2/8x+8 (1a)
It is also preferable that the elastic body 1 of the present invention satisfies the following formula (2a).
y>4/8x (2a)
It is also preferable that 7<x<26 is satisfied, and it is also preferable that 7<x<24 is satisfied.

The diameter y of the first protrusion 3 a is determined appropriately depending on the battery cell thickness and the expansion rate, and is preferably 1.45 times or more the thickness of the elastic body. Specifically, it is preferable that the following formula (4) is satisfied, and it is more preferable that the following formula (5) is satisfied.
4≦y≦14 (4)
6≦y≦12 (5)
By setting the diameter y to 4 mm or more, it is possible to more effectively prevent the elastic body from buckling when compressed, thereby reducing the reaction force, while by setting the diameter y to 14 mm or less, it is possible to more reliably prevent the elastic body from adhering to the surface of the battery cell.

When the elastic body 1 of the present invention is assembled into a battery module, the multiple protrusions 3 and the base material 2 create a gap (space) 2g between the surface of the battery cell or the restraining member and the elastic body 1 of the present invention (see Figure 2). The presence of this space absorbs deformation due to expansion and contraction of the battery cell and provides appropriate elastic support. The thickness t of the elastic body can be, for example, 1.05 to 7.70 mm, and is preferably 3.00 to 7.00 mm. In this specification, the "thickness of the elastic body" refers to the sum of the heights of the two protrusions arranged on the first and second surfaces of the base material, plus the thickness of the base material on which the two protrusions are erected. In other words, the "thickness of the elastic body" refers to the total thickness of the elastic body in the thickness direction.

In the elastic body 1 of the present invention, the thickness of each of the plurality of protrusions may be the same. That is, the height of the plurality of protrusions protruding from both surfaces of the base material may be the same on each surface.
Furthermore, the thickness of the multiple protrusions may increase from the center toward the outer periphery of the base material. That is, the height of the multiple protrusions protruding from both sides of the base material may increase from the center toward the outer periphery of the base material on each side. In this case, there may be protrusions whose thickness is constant from the center toward the outer periphery of the base material. For example, the thickness may change in one step or in several steps from the center toward the outer periphery of the base material, and preferably, the thickness changes continuously. This is because the expansion of a battery cell due to charging is not a local expansion of the surface of the battery cell, but rather, due to the spiral-shaped electrodes as described below, the surface of the battery cell expands in a curved shape with a constant curvature.

[Manufacturing elastic bodies for battery modules]

Below, a preferred example of a method for manufacturing the elastic body 1 of the present invention is described, but the method for manufacturing the elastic body 1 of the present invention is not limited to the method described below as long as the elastic body 1 of the present invention is obtained.

<Molding process>
In the molding step, the elastic body 1 of the present invention can be obtained, for example, by molding an elastomer material using a mold press and then vulcanizing the molded product.
The die press molding may be any method that is commonly used for producing elastic bodies. In the present invention, die press molding broadly encompasses molding methods using a die, such as compression molding, transfer molding, and injection molding.

[Battery module configuration]
A battery module to which the elastic body 1 of the present invention is applied will be described with reference to Figures 4(a) and (b). Figure 4(a) is an explanatory diagram schematically showing a battery module having battery cells in an initial state, and Figure 4(b) is an explanatory diagram schematically showing a battery module having battery cells that have expanded due to charging, with the arrangement of the internal battery cells 15 and elastic body 1 visible. This explanatory diagram also shows the state of the internal electrode body 15b for one of the five battery cells.
The electrode body 15b is an electrode body in which a positive electrode and a negative electrode are wound in a spiral shape with a separator sandwiched therebetween.

The battery module comprises a plurality of battery cells 15, restraining members 31, and elastic bodies 1 of the present invention arranged between the battery cells or between the battery cells and the restraining members. In the battery module, the battery cells 15 and elastic bodies 1 are arranged alternately and held in place by restraining members 31 (31a, 31b, 31c). The battery cells 15 comprise a housing 15a and an electrode body 15b inside the housing 15a. The battery cells 15 are rechargeable secondary batteries, and for example, lithium-ion secondary batteries can be suitably used.

When a battery cell 15 is charged, the internal electrode (negative electrode) absorbs ions and expands, causing the battery cell as a whole to expand primarily in one direction (horizontal in Figure 4(a)) (Figure 4(b)). The amount of expansion is greatest when the battery cell is fully charged. A charged battery cell contracts when discharged, ideally returning to the initial state shown in Figure 4(a). When this expansion and contraction of the electrode body is repeated, the distance between the electrodes inside the battery cell gradually increases, and battery performance deteriorates over time.

The restraining member 31 restrains the entire battery module. Metal is preferably used for the restraining member 31 (31a) to exert sufficient restraining force, but hard resin can also be used.

The present invention will now be described in detail based on the examples shown in Table 1 below, but the present invention is not limited to these.

[Example 1]
The elastic body shown in FIG. 1 was produced by the following method.
Ethylene propylene diene rubber (EPDM) was used as the elastomer material, and carbon black (model number: Asahi #60HN, manufactured by Asahi Carbon Co., Ltd.) was used as the filler. The EPDM and carbon black were mixed, and then an organic peroxide-based curing agent (product name: Perhexa 25B, manufactured by NOF Corporation) was added as a crosslinking agent (vulcanizing agent). The mixture was preformed into a rectangular shape using a mixing roll machine (manufactured by Yasuda Seiki Mfg. Co., Ltd.) and a super cutter (manufactured by Ogino Seiki Mfg. Co., Ltd.). This preform was placed in a mold, and the mold was clamped and pressed at a temperature of 190°C for 4 minutes, thereby allowing a crosslinking reaction (curing reaction) to occur while molding.
The details of the structure of the obtained elastic body are shown in the table below: In the elastic body of Example 1, the convex portions in the inner region and the convex portions outside thereof all have a thickness of 4.2 mm.

[Example 2]
The elastic body shown in FIG. 1 was produced in the same manner as in Example 1.
In this example, as shown in FIG. 13 , an elastic body was obtained in the same manner as in Example ₁ , except that the thickness t1 of the convex portion I in the inner region that contacts the outer periphery of the inner region and the thickness _t1 of the convex portion located outside the inner region were made thicker than the thickness _t2 of the convex portion located inside the convex portion I.
In detail, the thickness _t1 of the convex portion I and the thickness _t1 of the convex portions located outside the inner region were all set to 4.4 mm, and the thickness _t2 of the convex portions located inside the convex portion I were all set to 3.8 mm.

[Example 3]
The elastic body shown in FIG. 5 was produced in the same manner as in Example 1.
5, in this example, an elastic body was obtained in the same manner as in Example 1, except that the center distance x of the convex portions was made larger than that of the elastic body in Example 1 and the total number of convex portions was reduced. Note that the diameter y of the convex portions of the elastic body in Example 3 was the same as that of the elastic body in Example 1.

[Example 4]
The elastic body shown in FIG. 6 was produced in the same manner as in Example 1.
6, in this example, an elastic body was obtained in the same manner as in Example 1, except that the center distance x of the convex portions was made smaller than that of the elastic body in Example 1 and the total number of convex portions was increased. Note that the diameter y of the convex portions of the elastic body in Example 4 was the same as that of the elastic body in Example 1.

[Example 5]
The elastic body shown in FIG. 7 was produced in the same manner as in Example 1.
In this example, as shown in FIG. 7, an elastic body was obtained in the same manner as in Example 1, except that the diameter y of the convex portion and the center distance x were made larger than those of the elastic body in Example 1, and the total number of convex portions was reduced.

[Example 6]
The elastic body shown in FIG. 8 was produced in the same manner as in Example 1.
In this example, as shown in FIG. 8, an elastic body was obtained in the same manner as in Example 1, except that the diameter y of the convex portion and the center distance x were made larger than those of the elastic body in Example 5, and the total number of convex portions was reduced.

[Comparative Example]
The elastic body shown in FIG. 9 was produced in the same manner as in Example 1.
In the comparative example, an elastic body was obtained in the same manner as in example 1, except that the arrangement of the convex portions in the inner region was an arrangement different from the above-mentioned "regular arrangement." The diameter y and center distance x of the convex portions of the elastic bodies according to the comparative example and examples 1 to 6 are shown in Figure 10. Figure 10 is a graph plotting the diameter y and center distance x of the convex portions of the elastic bodies according to the comparative example and examples.

[Evaluation of load-displacement characteristics of elastic bodies]
The surface pressure of the elastic bodies obtained in Examples 1 to 6 and Comparative Example was measured under the following conditions, and the load-displacement characteristics of each elastic body were evaluated.
Compression testing machine: Universal material testing machine, model number: 588H (Instron)
Compression conditions: 0.5 to 60%
Test speed: 1 mm/min. Pre-compression was performed twice, and the measurement result of the third time was used.
In this evaluation, the surface pressure was measured at a low compression rate of 14% and a high compression rate of 45%. It is preferable that the surface pressure at a compression rate of 14% is not too low, and that the surface pressure at a compression rate of 45% is not too high. This load-displacement characteristic allows the elastic body to sufficiently repel relatively low restraint loads, such as those encountered during assembly in battery module manufacturing or battery module discharge, contributing to the stable maintenance of the stacked structure of the battery module. It also allows the elastic body to sufficiently absorb restraint loads during battery cell charging, avoiding high restraint loads (battery cell allowable limit loads) that could cause battery cell damage. The surface pressure was calculated based on the total contact area of the multiple protrusions that make up the elastic body.
The evaluation results are shown in Table 1. Graphs showing the load-displacement characteristics of the elastic bodies according to Example 1 and the comparative example are shown in Fig. 11, and graphs showing the load-displacement characteristics of the elastic bodies according to Examples 1 and 2 are shown in Fig. 12.

(Table notes)
The "total number of convex portions" is the total number of convex portions formed on one side of the base material, that is, the total number of convex portions on one side of the elastic body.
The "area ratio" is the ratio (percentage) of the area of the inner region to the area of one side of the base material portion.

As shown in Figure 11, in the comparative example elastic body, in which the convex portions in the inner region were not regularly arranged, the surface pressure rose to 5.0 MPa or more when compressed 45% in the stacking direction (high compression). In contrast, in the elastic bodies of Examples 1 to 6, in which the convex portions in the inner region were regularly arranged, the surface pressure was kept below 3.0 MPa even when compressed 45% in the stacking direction (high compression), demonstrating that the high restraining force was effectively absorbed. Furthermore, the elastic bodies of Examples 1 to 6 were able to exert a reaction force of 0.2 MPa or more even when compressed only 14% in the stacking direction (low compression).

From the above, it can be seen that by arranging the convex portions in the inner region of the elastic body in a specific, regular pattern, it is possible to ensure the reaction force during low compression while sufficiently absorbing the pressure during high compression, effectively suppressing the reaction force. Therefore, for example, by combining the selection of the elastomer material that makes up the elastic body with the elastic body shape of the present invention, it is possible to achieve load-displacement characteristics that are suitable for elastic bodies for battery modules, depending on the specifications of various battery modules.

1 Elastic body 2 Base material portion 2d First surface 2h Second surface IE Inner region OE Outer region 3 Convex portion 3a First convex portion 3b Second convex portion 15 Battery cell 15a Housing 15b Electrode body 2g Gap (space)
100 Battery module 31 Restraint member 31a First restraint member 31b Second restraint member 31c Connecting member

Claims (5)

An elastic body for a battery module that is disposed between adjacent battery cells and/or between a battery cell and a restraining member of a battery module including a plurality of battery cells and a restraining member,
The elastic body has a base portion and a plurality of convex portions protruding from both sides of the base portion, and when the elastic body is viewed in a plane, the elastic body is composed of an inner region in which the plurality of convex portions have the following regular arrangement, and an outer region other than the inner region,
the base material and the plurality of protrusions are integrally formed from the same elastomer,

[Regular array]
When the elastic body is viewed in a plane:
a plurality of first protrusions arranged at equal intervals in the longitudinal direction of the elastic body;
a plurality of second protrusions arranged at equal intervals in the longitudinal direction of the elastic body and positioned at four corners of a rectangle having the first protrusion at its center;
A repeat of a sequence consisting of :

heights of the first protrusions and the second protrusions protruding from the base portion increase from the center side to the outer periphery side of the base portion,
An elastic body for a battery module, wherein the thickness of the elastic body of the convex portion within the inner region that contacts the outer periphery of the inner region is the same as the thickness of the elastic body of the convex portion located outside the inner region, and the thickness is thicker than the thickness of the elastic body of the convex portion located inside the convex portion that contacts the outer periphery of the inner region . 2. The elastic body for a battery module according to claim 1, wherein the first convex portions and the second convex portions are cylindrical, and when the regular arrangement is viewed in a plan view, a shortest distance x (mm) from a center of the first convex portion to a center of the second convex portion and a diameter y (mm) of the first convex portion satisfy the following formulas ( 1 ) to (3):
y<7/8x+1/2 (1)
y>3/8x+3/8 (2)
x>6 (3) The elastic body for a battery module according to claim 2 , wherein the diameter y (mm) satisfies the following formula (4):
4≦y≦14 (4) The elastic body for a battery module according to claim 1, wherein the outer region is formed to surround the entire periphery of the inner region when the elastic body is viewed in a plan view. The elastic body for a battery module according to claim 1 , wherein the density of the convex portions in the outer region is lower than the density of the convex portions in the inner region.