WO2024143192A1

WO2024143192A1 - Battery pack cushioning member and production method for same

Info

Publication number: WO2024143192A1
Application number: PCT/JP2023/046120
Authority: WO
Inventors: 嗣典島; 史典江草; 由紀乃遠藤
Original assignee: タイガースポリマー株式会社
Priority date: 2022-12-27
Filing date: 2023-12-22
Publication date: 2024-07-04

Abstract

Provided are a battery pack cushioning member that has excellent thermal insulation properties and fire resistance and a production member for the battery pack cushioning member. A battery pack (20) is formed by stacking plate-shaped secondary batteries (10), (10), and cushioning members (21), (21) are provided between adjacent secondary batteries (10), (10). The cushioning members (21) include: a flat cushioning body (200) that is made from a cross-linked rubber; and a non-woven fabric (1) that is integrally layered onto the cushioning body (200). The non-woven fabric (1) carries heat-expandable, fire-resistant functional particles (4, 4). The functional particles (4), (4) expand when heated to improve the thermal insulation properties of the non-woven fabric (1).

Description

Cushioning member for battery pack and method of manufacturing same

The present invention relates to a cushioning member for a battery pack used in a battery pack, and a method for manufacturing the same.

Secondary batteries, which can be charged and discharged, are used in a variety of applications, including electric vehicles, home appliances, and mobile phones. Secondary batteries typically consist of an electrode assembly in which a positive electrode and a negative electrode are stacked and wound with a separator between them, and the electrode assembly is sealed in a container together with an electrolyte. In applications such as automobiles, it is common to electrically connect multiple such secondary batteries and use them as an integrated battery pack.

When plate-shaped secondary batteries are stacked to form a battery pack, a buffer member may be disposed between adjacent secondary batteries.
For example, Patent Document 1 discloses a technology for an assembled battery in which an adjacent member (2) is sandwiched between adjacent energy storage elements (secondary batteries) and the adjacent member (2) includes a plate-shaped elastic portion (26). With this assembled battery, deformation of the holding member caused by expansion of the energy storage elements (secondary batteries) is suppressed.

JP 2023-1756 A

However, secondary batteries can sometimes overheat or catch fire, but even in such cases, it is necessary to prevent the chain reaction of abnormal overheating and the spread of fire to adjacent secondary batteries.

However, in the prior art, the adjacent member (2) and elastic portion (26) may lack heat resistance or fire resistance, and if the secondary battery abnormally overheats or catches fire, the members may be burned or damaged by the high temperature or flames, and there is a risk that the chain reaction of abnormal overheating to adjacent secondary batteries or the spread of fire may not be sufficiently suppressed.

The object of the present invention is to provide a cushioning material for a battery pack that has excellent heat insulation and fire resistance, and a method for manufacturing the same.

After extensive research, the inventor discovered that the above problems could be solved by combining a cushioning material made of cross-linked rubber with a specific nonwoven fabric, and thus completed the present invention.

The present invention is a buffer member for a battery assembly in which plate-shaped secondary batteries are stacked, and is disposed between adjacent secondary batteries. The buffer member includes a flat-plate buffer made of cross-linked rubber and a nonwoven fabric laminated and integrated with the buffer, and the nonwoven fabric carries fire-resistant functional particles with thermal expansion properties. When heated, the functional particles expand, improving the heat insulating properties of the nonwoven fabric (first invention).

In the first invention, preferably, the nonwoven fabric includes long fibers made of synthetic resin with the functional particles integrated therein, and the long fibers have a diameter that changes in the longitudinal direction of the fibers, as if a plurality of large diameter portions and small diameter portions were alternately arranged and strung together like beads, and the small diameter portions are monofilaments formed of the synthetic resin, and the large diameter portions contain the functional particles (invention 2). Furthermore, in the second invention, preferably, the fiber diameter of the small diameter portion of the long fiber is equal to or less than the diameter of the functional particles contained in the large diameter portion, and the functional particles are integrated into the large diameter portion by being wrapped by the synthetic resin in a membrane, net, or fiber bundle form, or by being bonded by the synthetic resin (invention 3). Also, in the first invention, preferably, the functional particles are particles of aluminum hydrogen phosphite (invention 4). Also, in any of the first to fourth inventions, preferably, the cushioning member further includes aluminum glass cloth, and the aluminum glass cloth is disposed between the nonwoven fabric and the cushioning body (invention 5).

The present invention also relates to a battery pack in which plate-shaped secondary batteries are stacked, and a cushioning member for a battery pack according to any one of the first to fourth inventions is disposed between adjacent secondary batteries so that the nonwoven fabric blocks the gap between the cushioning body and the secondary batteries (a sixth invention).
The present invention also relates to a method for producing a cushioning member for an assembled battery according to the second invention, which includes a first step of heating and melting the synthetic resin or dissolving it in a solvent to liquefy it, and dispersing the functional particles in the liquefied synthetic resin, and a second step of spinning the liquid synthetic resin having the functional particles dispersed therein by a melt-blowing method or an electrospinning method to form long fibers into a nonwoven fabric, in which the nonwoven fabric is formed directly on the surface of the cushioning body in the second step to be integrated with the cushioning body (seventh invention).

The battery assembly cushioning member of the present invention (first invention) and the manufacturing method for the battery assembly cushioning member of the present invention (seventh invention) provide a battery assembly cushioning member with excellent heat insulation and fire resistance. Furthermore, a battery assembly (sixth invention) in which such a battery assembly cushioning member is disposed between secondary batteries prevents the other secondary batteries from catching fire or becoming abnormally overheated, even if the secondary battery abnormally overheats or catches fire.

Furthermore, in the case of the second aspect of the invention, a large amount of functional particles can be supported on the nonwoven fabric, which further improves the heat insulation and fire resistance. In addition, the functional particles are less likely to fall off the nonwoven fabric and contaminate the surroundings.
Furthermore, in the case of the third aspect of the invention, the thermal expansion of the functional particles occurs quickly, and the heat insulating property and fire resistance are further improved.
Furthermore, in the fourth and fifth aspects of the invention, the fire resistance of the nonwoven fabric is further improved.

FIG. 2 is a perspective view showing the appearance of a secondary battery. XX cross-sectional view showing the structure of a secondary battery. 1 is a schematic diagram showing a structure of a battery pack in which a cushioning member for a battery pack according to a first embodiment is incorporated; 2 is a cross-sectional view showing a structure of a cushioning member for a battery pack according to the first embodiment; FIG. 3 is a schematic diagram showing the structure of a nonwoven fabric used in the cushioning member for the battery pack of the first embodiment. FIG. FIG. 2 is a schematic diagram showing the structure of a large diameter portion and a small diameter portion of a long fiber. 1 is a micrograph showing the structure of an example of a nonwoven fabric. 1 is a micrograph showing the structure of nonwoven fabric Example 2. 1 is a micrograph showing the structure of nonwoven fabric Example 3. FIG. 6 is a cross-sectional view showing a structure of a cushioning member for a battery pack according to a second embodiment. FIG. 11 is a cross-sectional view showing a structure of a cushioning member for a battery pack according to a third embodiment.

The following describes embodiments of the invention with reference to the drawings, taking as examples an assembled battery used in an electric vehicle and a cushioning member for an assembled battery that is incorporated into the assembled battery. The invention is not limited to the individual embodiments shown below, and can be implemented by modifying the form.

Figures 1 and 2 show the appearance and structure of a secondary battery 10 that is incorporated into the battery pack. Figure 2 is a cross-sectional view taken along the line X-X in Figure 1. Figure 3 shows a schematic diagram of the structure of a battery pack 20 in which

secondary batteries

10, 10 are stacked. Figure 3 is drawn as viewed from the same direction as Figure 2.

As shown in FIG. 3, the battery pack 20 of this embodiment is configured by electrically connecting a plurality of

secondary batteries

10, 10 and integrating them with each other. The battery pack 20 is configured by stacking a plurality of flat

secondary batteries

10, 10. Typically, but not necessarily, the positive electrode member 13 and the negative electrode member 14 of each secondary battery are connected by a bus bar 23 to establish an electrical connection. In addition,

buffer members

21, 21 are arranged between the individual

secondary batteries

10, 10. The buffer member 21 may be provided with a cooling groove or the like. In addition, typically,

end plates

22, 22 are provided to sandwich the stacked structure of the

secondary batteries

10, 10 and the

buffer members

21, 21, and the stacked structure of the battery pack 20 is maintained by fastening the

end plates

22, 22 with fastening members such as bolts or bands. For the bus bar 23 and the end plates 22, known members can be used as appropriate.

The battery pack 20 can be housed in a battery case (not shown) and used in a vehicle such as a hybrid car. Typically, a battery case is used to send cooling air to cool the battery pack 20, thereby cooling each of the

secondary batteries

10, 10. The means for cooling the batteries is not limited to an air-cooled type that uses cooling air, but may be a liquid-cooled type that uses a cooling liquid. Although not shown in FIG. 3, a member for forming a passage for flowing the cooling liquid or cooling air along the batteries may be placed between the

secondary batteries

10, 10 so as to be stacked with the buffer member 21.

The cushioning member 21 will now be described. Fig. 4 shows a schematic diagram of the layered structure of the cushioning member 21. Fig. 4 is drawn as viewed from the same direction as Fig. 3.
The cushioning member 21 includes a cushioning body 200 and a nonwoven fabric 1 laminated and integrated with the cushioning body 200 .
The buffer 200 is made of cross-linked rubber. The rubber is preferably flame-retardant rubber. The buffer 200 is in the form of a flat plate. The shape of the plate of the buffer 200 is not particularly limited, but is typically rectangular, similar to the plate-shaped secondary battery 10.

The cushioning body 200 may be a solid rubber sheet or plate. In addition, grooves or protrusions may be provided on the surface of the cushioning body 200. In addition, holes or ducts may be provided inside the cushioning body 200, or the cushioning body 200 may be formed in a flat bag shape.

In the embodiment of FIG. 4, nonwoven fabric 1 is laminated and integrated on both sides of flat cushioning body 200 to form cushioning member 21. If necessary, nonwoven fabric 1 may be laminated and integrated on only one side of cushioning body 200. The means of integration is not particularly limited, and it is sufficient that cushioning body 200 and nonwoven fabric 1 are integrated to such an extent that they do not come apart when cushioning member 21 is incorporated into a battery pack. For example, integration may be achieved using an adhesive, pressure sensitive adhesive, double-sided tape, or the like, or by forming nonwoven fabric 1 directly on the surface of cushioning body 200. The cushioning body 200 may be placed in a bag-shaped nonwoven fabric to integrate the two.

The stacking form of the cushioning body 200 and the nonwoven fabric 1 may be such that the nonwoven fabric 1 is disposed in the portion where the secondary battery 10 and the cushioning body 200 face each other and press against each other. In other words, the nonwoven fabric 1 may be disposed so that it blocks the space between the cushioning body 200 and the secondary battery 10. To this extent, the cushioning body 200 may have a portion that is not covered by the nonwoven fabric 1, and the nonwoven fabric 1 may have a portion that protrudes from the cushioning body 200.

In the embodiment of FIG. 10, the cushioning member 28 is configured by integrating a nonwoven fabric 1 onto one side of the cushioning body 200. In this embodiment, an aluminum glass cloth 203 is disposed between the nonwoven fabric 1 and the cushioning body 200. The aluminum glass cloth is a material in which a woven fabric made of glass fiber and aluminum foil are laminated together. The aluminum foil may be formed by vapor deposition or the like.

In the embodiment of FIG. 11, the buffer 201 is housed in a bag-shaped nonwoven fabric 1 and fixed with an adhesive or the like as necessary to form a buffer member 29 in which the nonwoven fabric 1 is integrated with both sides of the buffer 201. If the nonwoven fabric 1 is bag-shaped, it is preferable because it is easier to integrate and it is easier to control the direction of propagation of gas or flame when flame or gas is emitted from the battery housed in the bag. In the embodiment of FIG. 11, the buffer 201 is hollow and bag-shaped, and liquid or gas can be introduced or removed from the inside of the buffer 201 via the joint 202, which can be used for pressurization or cooling.

The nonwoven fabric 1 contained in the

buffer members

21, 28, and 29 will be described in detail below.
The nonwoven fabric 1 carries fire-resistant

functional particles

4, 4 having thermal expansion. The fire-resistant

functional particles

4, 4 having thermal expansion expand when heated, improving the heat insulating property of the nonwoven fabric 1. The

functional particles

4, 4 are fire-resistant and will not burn for a predetermined period of time even when exposed to high temperatures such as flames. The expansion start temperature at which the

functional particles

4, 4 start to expand is set to be higher than the temperature during normal operation of the secondary battery 10, and the

functional particles

4, 4 do not expand when the secondary battery is operating normally, but are set to expand when the nonwoven fabric 1 is exposed to high temperatures due to abnormal overheating of the secondary battery or the occurrence of a fire. For example, the preferred range of the expansion start temperature of the fire-resistant

functional particles

4, 4 having thermal expansion can be set to 250°C to 400°C.

Furthermore, it is preferable that the nonwoven fabric 1 is permeable to gas or liquid. For example, when the nonwoven fabric 1 is placed facing a location through which cooling air passes, it is preferable that the nonwoven fabric 1 is configured to allow air to pass through.

Examples of

functional particles

4,4 that have thermal expansion properties include thermally expandable graphite and aluminum phosphite. The

functional particles

4,4 are inorganic particles that do not melt even when exposed to high temperatures and maintain their function as a fire-resistant insulating layer for a specified period of time (e.g., 10 to 30 minutes).

The form in which the nonwoven fabric 1 used in the cushioning member 21 carries the thermally expandable

functional particles

4, 4 is not particularly limited, and the functional particles may be carried by the fibers constituting the nonwoven fabric with a binder or the like.
Preferably, the thermally expandable

functional particles

4, 4 are supported so as to be integrated with the long fibers made of synthetic resin, as in the nonwoven fabric 1 of the embodiment shown in Fig. 5. When integrated in this manner, the functional particles are less likely to fall off, and air and liquids can easily pass through the nonwoven fabric even if a large amount of functional particles are supported.
The structure of the nonwoven fabric 1 according to the embodiment shown in FIG. 5 will now be described in detail.

The nonwoven fabric 1 of the embodiment shown in FIG. 5 is a nonwoven fabric containing long fibers made of synthetic resin with thermally expandable

functional particles

4, 4 integrated therein. Here, long fibers are long fibers in contrast to the short fibers in the fibers that make up the nonwoven fabric. Long fibers are also called filament yarns. Short fibers are called staple fibers, etc., and their length is generally several mm to several tens of cm, while long fibers are short fibers that have not been cut. Long fibers are typically spun by the meltblowing method, electrospinning method, or spunbonding method, and are stacked as they are to form a nonwoven fabric. Note that the nonwoven fabric 1 does not have to be composed only of long fibers, and may contain short fibers, or may be mixed so that the long fibers and short fibers are entangled.

Although not essential, it is preferable that the amount of

functional particles

4, 4 mixed with the nonwoven fabric 1 is approximately 10 to 500 g/m2.

The nonwoven fabric may be a single layer, or may be a laminated nonwoven fabric in which multiple nonwoven fabric layers, films, sheets, woven fabrics, etc. are laminated. The nonwoven fabric may be a composite nonwoven fabric in which a layer of nonwoven long fibers is laminated on a woven fabric or mesh material. The synthetic resin long fibers integrated with the

functional particles

4, 4 may be contained only in one of the nonwoven fabric layers. Preferably, as in the embodiment of FIG. 10, a nonwoven fabric or composite nonwoven fabric containing an aluminum glass cloth 203 and a layer of nonwoven long fibers may be laminated. The laminate of the aluminum glass cloth and the nonwoven fabric 1 has excellent fire resistance and heat insulation, and the nonwoven fabric becomes stronger and easier to handle.

In addition, all of the long fibers contained in nonwoven fabric 1 may be long fibers made of synthetic resin with functional particles integrated therein, but nonwoven fabric 1 may also contain other long fibers, for example, long fibers that do not have functional particles integrated therein.
Although not essential, the nonwoven fabric 1 of the present embodiment is a single-layer nonwoven fabric obtained by electrospinning long fibers made of synthetic resin with functional particles integrated therein.

Fig. 5 shows a schematic structure of a nonwoven fabric 1 that can be used in the cushioning member 21 for a battery pack of the first embodiment. Fig. 7 shows a microscope photograph of an example of the nonwoven fabric of the embodiment of Fig. 5. In Fig. 5, the

small diameter portions

3, 3 are represented by a single solid line.
The long fibers contained in the nonwoven fabric 1 have diameters that change in the longitudinal direction of the fibers so that a plurality of

large diameter portions

2, 2 and

small diameter portions

3, 3 are arranged alternately. In other words, the long fibers are fibers that are structured like a string of

large diameter portions

2, 2 and

small diameter portions

3, 3. That is, the diameters of the long fibers change in the longitudinal direction of the fibers.

The

small diameter portions

3, 3 of the long fibers are monofilaments formed from the synthetic resin. There are no particular limitations on the synthetic resin as long as it can be made into fibers, but it is preferable that the synthetic resin is suitable for manufacturing long fibers by the melt-blowing method or the electrospinning method. In addition, it is preferable that the synthetic resin is a resin that adheres to the functional particles described below. For example, polyurethane resin or polyvinyl chloride resin can be used as the synthetic resin that is the raw material for the long fibers.

The monofilament that forms the

small diameter portion

3, 3 may be composed only of the synthetic resin described above, but may also contain other compounding materials, such as reinforcing materials or bulking materials, particles with a diameter smaller than the diameter of the small diameter portion, or chemicals that improve the properties of the synthetic resin.

Although not essential, the fiber diameter of the

small diameter portions

3, 3 is preferably 100 nanometers or more and 10 micrometers or less. The fiber diameter of the

small diameter portions

3, 3 is particularly preferably 500 nanometers or more and 3 micrometers or less. Here, the fiber diameter refers to the diameter of the fiber measured in a direction perpendicular to the extension direction of the fiber, and is determined by taking a microphotograph of the nonwoven fabric 1 and measuring the fiber diameter of the small diameter portion on the photograph. Preferably, the fiber diameter is measured at 10 to 20 small diameter portions, and the average of these measurements is treated as the fiber diameter of the small diameter portion.

The

large diameter portion

2, 2 contains thermally expandable

functional particles

4, 4. Although not essential, at least a portion of the

large diameter portion

2, 2 is formed by a plurality of

functional particles

4, 4 being solidified into a string-like or dumpling-like shape by the synthetic resin. Here, the term "string-like" means that, with respect to the shape of the large diameter portion, the length in the direction of extension of the fiber is greater than the length in the direction perpendicular to the direction of extension of the fiber, preferably three times or more. Also, the term "dumpling-like" means that, with respect to the shape of the large diameter portion, the length in the direction of extension of the fiber is approximately the same as the length in the direction perpendicular to the direction of extension of the fiber, preferably 1/2 or more and 2 times or less. Note that the long fiber may have a large diameter portion that does not contain functional particles or that contains only one functional particle.

The diameter of the

large diameter portion

2, 2 is larger than the fiber diameter of the

small diameter portion

3, 3. The diameter of the large diameter portion is the diameter measured in a direction perpendicular to the extension direction of the fiber. Preferably, the diameter is measured at 10 to 20 large diameter portions, and the average of the diameters is treated as the diameter of the large diameter portion. Although not essential, the diameter of the

large diameter portion

2, 2 is preferably 150 nanometers or more and 300 micrometers or less. Particularly preferably, the diameter of the

large diameter portion

2, 2 is 1 micrometer or more and 50 micrometers or less. Also, preferably, the diameter of the

large diameter portion

2, 2 is 3 to 20 times, and particularly preferably 4 to 10 times, the fiber diameter of the

small diameter portion

3, 3.

Figure 6 shows a schematic structure of the

large diameter portion

2, 2 and the

small diameter portion

3, 3 in the long fiber. The large diameter portion 2 contains a plurality of thermally expandable

functional particles

4, 4. In the illustrated form, these

functional particles

4, 4 are wrapped or bonded with the same synthetic resin as that constituting the small diameter portion, and are solidified into a string-like or ball-like shape. In the

large diameter portion

2, 2, the

functional particles

4, 4 may be bonded to each other by the synthetic resin, or the

functional particles

4, 4 may be wrapped in a film-like or net-like synthetic resin. In the

large diameter portion

2, 2, only one functional particle may be present in the radial direction of the fiber, or multiple functional particles may be present in the radial direction of the fiber. At the end of the

large diameter portion

2, 2, the large diameter portion 2 and the small diameter portion 3 are continuous so that the synthetic resin contained in the large diameter portion becomes the monofilament of the

small diameter portion

3, 3 as it is.

The

functional particles

4, 4 contained in the

large diameter portion

2, 2 have thermal expansion and fire resistance. That is, in the nonwoven fabric 1 of this embodiment, particles having thermal expansion are used as functional particles. Examples of particles having thermal expansion include thermally expandable microcapsules, thermally expandable graphite, and aluminum phosphite. Examples of aluminum phosphite particles having thermal expansion include "APA-100" from Taihei Chemical Industry Co., Ltd. Among aluminum phosphite particles, aluminum hydrogen phosphite particles (such as "NSF" from Taihei Chemical Industry Co., Ltd.) can be preferably used. These particles have the property of expanding when heated to a predetermined temperature. If the

large diameter portion

2, 2 contains particles having thermal expansion, when the nonwoven fabric is heated, the

large diameter portion

2, 2 expands and changes to make the voids in the nonwoven fabric smaller and narrower, resulting in a change in the breathability of the nonwoven fabric. In addition, as the

functional particles

4, 4 expand, the particles themselves become foamed and hollow, making them less likely to transmit heat, improving the insulating properties of the nonwoven fabric 1.

Preferably, the fiber diameter Ds of the

small diameter portion

3, 3 is equal to or smaller than the diameter Dp of the

functional particles

4, 4 contained in the

large diameter portion

2, 2. The fiber diameter Ds of the

small diameter portion

3, 3 and the diameter Dp of the

functional particles

4, 4 may be substantially the same. In the present invention, the diameter Dp of the

functional particles

4, 4 refers to the volume average diameter. The diameter Dp of the

functional particles

4, 4 contained in the large diameter portion is typically 300 nanometers or more and 200 micrometers or less. In addition, although not essential, the fiber diameter Ds of the

small diameter portion

3, 3 is preferably 1/100 or more of the diameter Dp of the

functional particles

4, 4.

An example of a method for manufacturing the nonwoven fabric 1 of the above embodiment will be described. The nonwoven fabric 1 can be manufactured by applying the meltblowing method or the electrospinning method.

First, in the first step, liquefied synthetic resin is mixed with thermally expandable functional particles. The synthetic resin is liquefied by heating to melt it or by dissolving it in a solvent. The

functional particles

4, 4 are mixed and dispersed in the liquefied synthetic resin. The functional particles may be kneaded into the synthetic resin in advance, which is then heated and melted to obtain a liquid synthetic resin with the functional particles dispersed therein, or the synthetic resin may be dissolved in a solvent or the like to liquefy it, and then the functional particles are mixed and dispersed therein.

In this embodiment, polyurethane resin is dissolved in a solvent to make it liquid, and aluminum hydrogen phosphite powder (manufactured by Taihei Chemical Industry Co., Ltd., NSF, volume average diameter 5 micrometers) is mixed into it as

functional particles

4,4, and stirred to disperse.

Next, in the second step, following the first step, the liquid synthetic resin in which the

functional particles

4, 4 are dispersed is spun into long fibers by melt-blowing or electrospinning, and then deposited to form a nonwoven fabric.

The liquid synthetic resin discharged from the spinning nozzle is stretched by centrifugal force, gravity, electrostatic force, etc. to become thin fibers. These thin fibers become the

small diameter parts

3, 3 of the long fibers. At this time, when the

functional particles

4, 4 are discharged from the nozzle together with the liquid synthetic resin, the part where the

functional particles

4, 4 are gathered solidifies into a string-like or ball-like shape to become the

large diameter parts

2, 2, while the excess synthetic resin is stretched to form the

small diameter parts

3, 3, and the

large diameter parts

2, 2 and the

small diameter parts

3, 3 are strung together to form a continuous long fiber. The long fibers that have been formed are solidified as the solvent evaporates and the temperature drops, and are deposited on the base of the spinning device, producing the nonwoven fabric 1.

Although not essential, the second step may be performed using a rubber sheet or rubber plate that will become the cushioning body 200 as a substrate, and the nonwoven fabric 1 may be formed directly on the surface of the cushioning body 200 to be integrated with the cushioning body 200. In this way, the step of integrating the cushioning body 200 and the nonwoven fabric 1 can be omitted, making the nonwoven fabric 1 easier to handle. When forming the nonwoven fabric 1 by spinning the rubber material that will become the cushioning body 200 using an electrospinning method, it is preferable to adjust the conductivity of the rubber material itself or adjust the electrostatic charge by a spray treatment or the like.

(Nonwoven Fabric Examples)
In the embodiment, aluminum hydrogen phosphite "NSF" (average particle diameter 5 micrometers) was used as the functional particle, and a nonwoven fabric 1 was obtained in which the diameter of the

large diameter parts

2,2 was about 2 to 10 micrometers (average diameter 6 micrometers) and the diameter of the

small diameter parts

3,3 was about 0.5 to 1.5 micrometers (average diameter 0.9 micrometers). The amount of

functional particles

4,4 blended into the obtained nonwoven fabric 1 was about 100 g/m2. If a large number of long fibers are laminated, the amount of

functional particles

4,4 blended per unit area in the nonwoven fabric 1 can be increased. FIG. 7 shows a micrograph of the nonwoven fabric of the embodiment. In FIG. 7, only a small portion of the layers in the thickness direction of the nonwoven fabric is photographed so that the form of the fibers can be clearly seen. The same is true for FIGS. 8 and 9.

By adjusting the amount of functional particles, the viscosity and discharge speed of the liquid synthetic resin, the nozzle diameter, the applied voltage of static electricity, the distance from the nozzle to the base, the ambient temperature, etc., it is possible to adjust the size, length, diameter, and ratio of the

large diameter portion

2, 2 and the

small diameter portion

3, 3.

When the nonwoven fabric 1 is manufactured using the melt-blowing method or the electrospinning method, the synthetic resin is drawn out from the portion that will become the large diameter portion to the portion that will become the small diameter portion during spinning, so that less synthetic resin remains in the large diameter portion. This causes the synthetic resin coating that covers the functional resin in the large diameter portion to become thinner or reticulated. By making the synthetic resin coating thinner or reticulated, the thermal expansion properties of the functional particles can be exerted more quickly and effectively, which is preferable.

The secondary battery 10 will now be described.
As shown in Figs. 1 and 2, the secondary battery 10 is configured by sealing an electrode body 11 together with an electrolyte (not shown) in a container 12. The electrode body 11 is one power generation unit. As in this embodiment, one electrode body 11 may be housed in the container 12, or a plurality of

electrode bodies

11, 11 may be housed in the container 12. The secondary battery 10 is sometimes called a single cell or a battery element in contrast to the assembled battery 20. The shape of the secondary battery 10 is not particularly limited, and may be cylindrical, but is preferably flat as in this embodiment. A flat secondary battery is sometimes called a rectangular battery.

The electrode body 11, electrolyte, container 12, positive electrode member 13, and negative electrode member 14 in the secondary battery 10 can be appropriately made from known materials. These members can be assembled into the secondary battery 10 by known methods.

The electrode body 11 includes a positive electrode, a separator, and a negative electrode. The positive electrode, separator, and negative electrode are in sheet form. The positive electrode and negative electrode are stacked with the separator sandwiched between them, and the stacked electrodes are wound up to form the electrode body 11. In this embodiment, the electrode body is flat (plate-shaped).

The positive electrode, negative electrode, and separator may be made of known materials as appropriate.
The positive electrode is conductive and includes a positive electrode active material (e.g., a lithium transition metal complex oxide), the negative electrode is conductive and includes a negative electrode active material (e.g., graphite), and the separator may be a porous resin film.

The electrolyte can also be appropriately selected from known electrolytes. The electrolyte may be a non-aqueous electrolyte solution containing a non-aqueous solvent (e.g., ethylene carbonate) and an electrolyte salt (e.g., an inorganic lithium salt).

There are no particular limitations on the container 12 as long as it can enclose the electrode body 11 and the electrolyte. The container 12 may be made of resin or metal.

The positive electrode of the electrode body 11 is connected to the positive electrode member 13, and the positive electrode member 13 is exposed to the outside of the container 12. The negative electrode of the electrode body 11 is connected to the negative electrode member 14, and the negative electrode member 14 is exposed to the outside of the container 12. The positive electrode member 13 and the negative electrode member 14 become external terminals of the secondary battery 10 and are electrically connected to the bus bar 23, etc.

When assembling the

secondary batteries

10, 10 and the

buffer members

21, 21 to manufacture the battery pack 20, they are alternately stacked to obtain the battery pack 20 with a stacked structure as shown in FIG. 3. At that time, the

buffer members

21, 21 are arranged between adjacent

secondary batteries

10, 10 so that the nonwoven fabric 1 blocks the gap between the buffer body 200 and the secondary batteries 10. Furthermore, if the buffer member 21 includes aluminum glass cloth 203, the aluminum glass cloth 203 is arranged between the nonwoven fabric 1 and the buffer body 200.

The function and effect of the cushioning member 21 provided with the nonwoven fabric 1 will now be described.
The nonwoven fabric 1 used in the cushioning member 21 of the above embodiment is a fire-resistant nonwoven fabric that carries heat-expandable fire-resistant functional particles, and the functional particles expand when heated, improving the heat insulating property of the nonwoven fabric. That is, the heat insulating property of the nonwoven fabric 1 is improved when the battery abnormally overheats or catches fire, compared to when the battery is in normal operation. Therefore, in the secondary battery 10 of the above embodiment, when abnormal overheating such as ignition occurs, the functional particles expand when heated, improving and increasing the heat insulating property of the nonwoven fabric, and the nonwoven fabric itself becomes fire-resistant and maintains its shape, so that a cushioning member for a battery pack with excellent heat insulating property and fire resistance is obtained.
Furthermore, in a battery pack in which such a battery pack cushioning member is disposed between the secondary batteries, even if abnormal overheating or ignition occurs in one of the secondary batteries, the other secondary batteries are prevented from burning or overheating.

In particular, since such nonwoven fabric 1 is laminated with a cross-linked rubber buffer, it has particularly excellent heat insulation and fire resistance. The cross-linked rubber buffer 200 does not melt and disappear when heated, so even if it is exposed to abnormal overheating or flames, it is unlikely to immediately lose its shape and function as a plate-shaped buffer. Therefore, even if the nonwoven fabric is exposed to flames or gas ejections, the buffer 200 supports/backs up the nonwoven fabric 1, and the fire-resistant and heat-insulating nonwoven fabric 1 is reliably present between adjacent batteries, effectively suppressing chain reactions of abnormal overheating and spreading of fire in the batteries.

Furthermore, when the nonwoven fabric 1 used in the cushioning member 21 contains long fibers made of synthetic resin with

functional particles

4, 4 integrated therein, the diameter of the long fibers changes in the longitudinal direction of the fibers as if multiple

large diameter sections

2, 2 and

small diameter sections

3, 3 were arranged alternately and strung together like beads, the

small diameter sections

3, 3 are monofilaments formed from the synthetic resin, and the

large diameter sections

2, 2 contain

functional particles

4, 4, a large amount of functional particles can be supported on the nonwoven fabric, and the fire resistance is further improved. In addition, the functional particles are less likely to fall off the nonwoven fabric, making it less likely for the functional particles to contaminate the surroundings.

Furthermore, when the fiber diameter of the

small diameter portion

3, 3 of the long fiber is equal to or smaller than the diameter of the

functional particles

4, 4 contained in the

large diameter portion

2, 2, and the

functional particles

4, 4 are wrapped in a film-like, mesh-like, or fiber-bundle-like synthetic resin, or are bonded with the synthetic resin and integrated into the

large diameter portion

2, 2, the synthetic resin covering the functional particles becomes very thin, so that the thermal expansion and heat insulation of the functional particles are improved quickly, and the fire resistance and fire resistance are further improved.

Furthermore, when the functional particles are aluminum hydrogen phosphite particles, the expanded functional particles change the nonwoven fabric 1 into a fire-resistant and insulating heat insulating layer when heated, further improving the fire resistance. If the functional particles are insulating, there is no risk of the expanded functional particles causing a short circuit between the positive and negative electrodes of the battery, which is preferable. Furthermore, if the functional particles are aluminum hydrogen phosphite particles, the fire-resistant particles can reliably maintain their expanded form even when exposed to high temperatures during a battery fire, further improving the fire resistance and fire resistance.

Furthermore, when the buffer material includes an aluminum glass cloth 203 and the aluminum glass cloth 203 is disposed between the nonwoven fabric 1 and the buffer body 200, the fire resistance and the resistance to spreading of fire are more reliably improved.
Although the aluminum glass cloth itself is easily burned when exposed to flames, etc., when the nonwoven fabric 1 is provided on the flame side, the amount of heat reaching the aluminum glass cloth is reduced, making the aluminum glass cloth less susceptible to burn damage, due to the fire resistance and heat insulation properties exhibited by the nonwoven fabric 1. In addition, the aluminum glass cloth serves as a back-up material for the nonwoven fabric 1, and even if the nonwoven fabric 1 is exposed to flames or gas ejection, the nonwoven fabric 1 is less likely to collapse/scatter, and the fire resistance and heat insulation properties of the cushioning material are maintained at a high level.

Even if the nonwoven fabric 1 is thin and easily torn, by forming the above-mentioned nonwoven fabric 1 by electrospinning using the aluminum glass cloth 203 as a base material and laminating the two together, the nonwoven fabric 1 will be less likely to tear, and will be easier to handle when assembling the buffer member or the battery pack. From the viewpoint of fire resistance and heat insulation, when laminating the aluminum glass cloth 203 and the nonwoven fabric 1, it is preferable to laminate them in the order of nonwoven fabric 1, aluminum foil, and glass cloth from the side facing the battery.

Furthermore, if the buffer member 21 is arranged between adjacent

secondary batteries

10, 10 so that the nonwoven fabric 1 blocks the gap between the buffer 200 and the secondary battery 10, and a battery pack is constructed in which plate-shaped secondary batteries are stacked, in the event of abnormal overheating or ignition of the secondary battery, the nonwoven fabric 1 will exhibit fire resistance and heat insulation properties to prevent the buffer from burning, and the spread of fire and abnormal overheating of the other

secondary batteries

10, 10 will be prevented.

In addition, if the nonwoven fabric 1 is formed directly on the surface of the cushioning body 200 by meltblowing or electrospinning and integrated with the cushioning body, the cushioning member 21 with excellent fire resistance and heat insulation properties can be efficiently manufactured. In addition, if the nonwoven fabric 1 is formed integrally with the cushioning body 200, the nonwoven fabric 1 is less likely to tear during assembly of the battery, improving handling.

The invention is not limited to the above-described embodiment, and can be implemented with various modifications. Other embodiments of the invention are described below, but in the following description, the differences from the above-described embodiment will be mainly described, and detailed descriptions of similar parts will be omitted. Furthermore, these embodiments can be implemented by combining parts with each other, or by substituting parts.

Examples of the manner in which the nonwoven fabric 1 is attached to the cushioning body 200 include attaching it to one or both sides of the plate-shaped cushioning body, and forming it into a bag-like shape, but the manner in which it is attached is not limited to these. For example, the nonwoven fabric 1 may be attached to the cushioning body 200 in a form in which it is folded into a U-shape so as to cover two sides corresponding to the two sides of the flat plate. Alternatively, the nonwoven fabric 1 may be attached by wrapping it around the cushioning body 200.

There is no particular limitation on the technical field in which the secondary battery 10 is used, and the secondary battery 10 can be applied to technical fields other than those exemplified in the above embodiment.
For example, the secondary battery 10 can be used in electric vehicles and hybrid vehicles, but the use of the battery or battery pack is not limited to automobiles. For example, the secondary battery can also be used in electric bicycles. The secondary battery or battery pack may be used as a power source for trains, ships, and aircraft. The secondary battery or battery pack may also be used as a backup power source for computers, an auxiliary storage battery for wind power generation equipment or solar power generation equipment, an auxiliary power source or backup power source for industrial equipment, and the like.
The secondary battery may be, for example, a lithium ion battery, but may also be an all-solid-state battery.

In addition, for example, in the above embodiment, the long fibers contained in the nonwoven fabric 1 are simply in contact with each other at the intertwined portions, but the long fibers may be bonded to each other at the intertwined portions. For example, the

large diameter portions

2, 2 may be stuck together at the intertwined portions, or three or more (preferably four or more)

small diameter portions

3, 3 may be connected to one large diameter portion in appearance. With such a structure, the

small diameter portions

3, 3 are connected in a network shape between the

large diameter portions

2, 2, making it easier to maintain the three-dimensional structure of the nonwoven fabric 1 and providing good breathability.

Other examples of the nonwoven fabric 1 produced under different production conditions will be described below.
(Nonwoven Fabric Example 2)
8 is a micrograph showing the structure of the nonwoven fabric of Example 2, which was manufactured under different manufacturing conditions. The manufacturing conditions were adjusted so that the long fibers were thicker overall than in the above-mentioned Examples. The synthetic resin is thermoplastic polyurethane resin (TPU), the functional particles are "NSF" (average particle size 5 micrometers), and the fabrication is performed by electrospinning, which are the same as in the above-mentioned Examples.

In the nonwoven fabric of Example 2, the diameter of the

large diameter portions

2, 2 was approximately 2 to 15 micrometers (average diameter 8 micrometers), and the diameter of the

small diameter portions

3, 3 was approximately 0.5 to 1.8 micrometers (average diameter 1.0 micrometer). In addition, in the nonwoven fabric of Example 2, there were also portions where three or more small diameter portions extended so as to branch out from the large diameter portion.

(Nonwoven Fabric Example 3)
9 is a micrograph showing the structure of the nonwoven fabric of Example 3, which was manufactured under different manufacturing conditions. Compared to the above-mentioned examples, the amount of functional particles was reduced, and the manufacturing conditions were adjusted. The synthetic resin is thermoplastic polyurethane resin (TPU), the functional particles are "NSF" (average particle size 5 micrometers), and the fabrication is performed by electrospinning, which are the same as the above-mentioned examples.

In the nonwoven fabric of Example 3, the diameter of the

large diameter portions

2, 2 was approximately 3 to 8 micrometers (average diameter 5 micrometers), and the diameter of the

small diameter portions

3, 3 was approximately 0.3 to 1.0 micrometers (average diameter 0.6 micrometers). Also, in the nonwoven fabric of Example 3, there were portions where three or more small diameter portions extended so as to branch out from the large diameter portion.

The nonwoven fabrics of Examples 1, 2, and 3 all had moderate breathability, and when exposed to hot air (approximately 800°C), the functional particles expanded to form a fire-resistant insulating layer with almost no breathability, improving the insulation.

In addition, in the above embodiment, a single-layer nonwoven fabric containing thermally expandable functional particles is exemplified, but the nonwoven fabric may be a multi-layer nonwoven fabric having a layer that does not contain functional particles. For example, a two-layer nonwoven fabric may be formed by laminating an aramid fiber mesh material as a support layer on the above-mentioned nonwoven fabric.

The support layer is effective in improving the mechanical properties of the nonwoven fabric layer containing the thermally expandable particles. In particular, if the support layer is made of fibers made of a material that is more heat resistant than the synthetic resin that is the material of the long fibers of the nonwoven fabric, such as aramid fibers or metal fibers, it is possible to prevent the functional particles from being easily released from the constraint of the long fibers when the functional particles expand due to exposure to high temperatures. When providing a support layer, it is particularly preferable to provide the support layer on the opposite side of the nonwoven fabric 1 from the secondary battery.

In the above embodiment, the functional particles have been described as having thermal expansion and fire resistance, but the functions of the functional particles are not limited to thermal expansion. For example, the functional particles may be particles that have water retention and water absorption properties in addition to thermal expansion. In this case, it is possible to increase the water absorption properties of the nonwoven fabric and to produce a cooling effect by evaporating the absorbed moisture.

The battery pack cushioning member of the above embodiment is incorporated into battery packs used as power sources for electric vehicles, etc., and can prevent the battery from catching fire, making it highly useful in industry.

Reference Signs List 1 Nonwoven fabric 2 Large diameter portion 3 Small diameter portion 4 Functional particle 10 Secondary battery 11 Electrode body 12 Container 13 Positive electrode member 14 Negative electrode member 20 Battery pack 21 Buffer member 200 Buffer body 203 Aluminum glass cloth 22 End plate

Claims

A battery pack cushioning member disposed between adjacent secondary batteries in a battery pack in which plate-shaped secondary batteries are stacked, comprising:
The cushioning member includes a flat cushioning body made of crosslinked rubber and a nonwoven fabric laminated and integrated with the cushioning body,
The nonwoven fabric supports heat-expandable, fire-resistant functional particles, and the functional particles expand when heated, improving the heat insulating properties of the nonwoven fabric.
Cushioning material for battery packs.
The nonwoven fabric is
The functional particles are integrated into long fibers made of a synthetic resin,
The long fibers have diameters that vary in the longitudinal direction of the fibers, as if a plurality of large diameter portions and small diameter portions were alternately arranged and strung together,
the small diameter portion is a monofilament formed from the synthetic resin,
The large diameter portion contains the functional particles.
The cushioning member for a battery pack according to claim 1 .
a fiber diameter of the small diameter portion of the long fiber is equal to or smaller than a diameter of the functional particle included in the large diameter portion,
the functional particles are wrapped in the synthetic resin in a film-like, net-like, or fiber-bundle-like form, or are bonded by the synthetic resin, and are integrated with the large diameter portion;
The cushioning member for a battery pack according to claim 2 .
2. The cushioning member for a battery pack according to claim 1, wherein the functional particles are aluminum hydrogen phosphite particles.
Furthermore, the buffer member includes an aluminum glass cloth,
5. The cushioning member for a battery pack according to claim 1, wherein an aluminum glass cloth is disposed between the nonwoven fabric and the cushioning body.
A battery pack in which plate-shaped secondary batteries are stacked,
The cushioning member for a battery pack according to any one of claims 1 to 4 is disposed between adjacent secondary batteries so that the nonwoven fabric shields the cushioning body from the secondary batteries.
Battery pack.
A method for producing the cushioning member for a battery pack according to claim 2, comprising the steps of:
a first step of heating the synthetic resin to melt it or dissolving it in a solvent to liquefy it, and dispersing the functional particles in the liquefied synthetic resin;
A second step, which follows the first step, is to spin the liquid synthetic resin having the functional particles dispersed therein into long fibers by a melt-blowing method or an electrospinning method, thereby forming a nonwoven fabric;
In the second step, the nonwoven fabric is directly formed on the surface of the cushioning body to be integrated with the cushioning body.
A method for manufacturing a cushioning member for a battery pack.