Cushioning member for battery pack and method of manufacturing the same

Abstract

To provide a cushioning member for a battery pack having excellent heat insulation and fire resistance, and a method for manufacturing the same.SOLUTION: In a battery pack 20 in which plate-like secondary batteries 10, 10 are stacked, cushioning members 21, 21 are disposed between adjacent secondary batteries 10, 10. The cushioning member 21 includes a flat cushioning body 200 made of cross-linked rubber, and a nonwoven fabric 1 laminated and integrated with the cushioning body 200. The nonwoven fabric 1 carries fire-resistant functional particles 4, 4 having thermal expansion properties, and the functional particles 4, 4 expand when heated, improving the heat insulating properties of the nonwoven fabric 1.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a buffer member for a battery pack used in a battery pack and a method for manufacturing the same.

Background Art

[0002] Rechargeable secondary batteries are used in a variety of applications such as electric vehicles, household appliances, and mobile phones. A secondary battery generally has an electrode body in which a positive electrode and a negative electrode are laminated and wound with a separator interposed therebetween, and is enclosed in a container together with an electrolyte. In applications such as automobiles, it is common to use a plurality of such secondary batteries as an integrated battery pack that is electrically connected.

[0003] When a battery pack is configured by stacking plate-shaped secondary batteries, a buffer member may be disposed between adjacent secondary batteries. For example, Patent Document 1 discloses a battery pack technology in which an adjacent member (2) is sandwiched between adjacent power storage elements (secondary batteries), and the adjacent member (2) includes a plate-shaped elastic portion (26). According to this battery pack, deformation of the holding member due to expansion of the power storage element (secondary battery) is suppressed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] By the way, a secondary battery may cause abnormal overheating or ignition. Even in such a case, it is required to suppress the chain of abnormal overheating and the spread of fire to adjacent secondary batteries.

[0006] However, the above-mentioned adjacent member (2) and elastic part (26) in the prior art may lack heat resistance and fire resistance. When abnormal overheating or ignition occurs in the secondary battery, the members may be burned out or damaged by high temperature or fire, and there is a risk that the suppression of the chain of abnormal overheating or the spread of fire to adjacent secondary batteries may be insufficient.

[0007] An object of the present invention is to provide a buffer member for a battery pack excellent in heat insulation and fire resistance and a method for manufacturing the same.

Means for Solving the Problems

[0008] As a result of intensive studies, the inventor has found that the above problems can be solved by combining a buffer body made of cross-linked rubber and a specific non-woven fabric, and has completed the present invention.

[0009] The present invention is a buffer member for a battery pack disposed between adjacent secondary batteries in a battery pack in which plate-shaped secondary batteries are stacked. The buffer member includes a flat buffer body made of cross-linked rubber and a non-woven fabric laminated and integrated with the buffer body. The non-woven fabric carries heat-expandable fire-resistant functional particles, and the functional particles expand by heating to improve the heat insulation of the non-woven fabric. It is a buffer member for a battery pack. (First Invention)

[0010] In the first invention, preferably, the non-woven fabric contains long fibers made of a synthetic resin integrated with the functional particles, and the long fibers have a diameter that changes in the longitudinal direction of the fiber as if a plurality of large-diameter portions and small-diameter portions are alternately arranged and connected in a chain-like manner. The small-diameter portion is a monofilament formed of the synthetic resin, and the large-diameter portion contains the functional particles (second invention). Further, 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 wrapped by the synthetic resin formed in a film shape, a net shape, or a bundle shape of fibers, or adhered by the synthetic resin and integrated into the large-diameter portion (third invention). Also, in the first invention, preferably, the functional particles are particles of aluminum hydrogen phosphite (fourth invention). Further, in any one of the first to fourth inventions, preferably, the buffer member further includes an alumina glass cloth, and an alumina glass cloth is disposed between the non-woven fabric and the buffer body (fifth invention).

[0011] The present invention also relates to a battery pack in which plate-shaped secondary batteries are stacked, and between adjacent secondary batteries, a buffer member for a battery pack according to any one of the first to fourth inventions is disposed such that the non-woven fabric blocks the space between the buffer body and the secondary battery (sixth invention). The present invention also relates to a method for manufacturing a buffer member for a battery pack according to the second invention, including 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, following the first step, of spinning the liquid synthetic resin in which the functional particles are dispersed into long fibers by a melt blowing method or an electrospinning method to form a non-woven fabric. In the second step, the non-woven fabric is directly formed on the surface of the buffer body and integrated with the buffer body, which is a method for manufacturing a buffer member for a battery pack (seventh invention).

Advantages of the Invention

[0012] According to the buffer member for assembled battery of the present invention (the first invention) and the manufacturing method of the buffer member for assembled battery of the present invention (the seventh invention), a buffer member for assembled battery excellent in heat insulation and fire resistance can be obtained. Further, an assembled battery (the sixth invention) in which such a buffer member for assembled battery is disposed between secondary batteries suppresses the spread of fire and abnormal overheating of other secondary batteries even if abnormal overheating or ignition of a secondary battery occurs.

[0013] Furthermore, in the case of the second invention, a large amount of functional particles can be supported on the nonwoven fabric, and the heat insulation and fire resistance are further enhanced. Also, the functional particles are less likely to fall off from the nonwoven fabric, and it is less likely to contaminate the surroundings. Furthermore, in the case of the third invention, the thermal expansion of the functional particles occurs promptly, and the heat insulation and fire resistance are further enhanced. Furthermore, in the case of the fourth and fifth inventions, the fire resistance of the nonwoven fabric is further enhanced.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Embodiments for Carrying Out the Invention

[0015] Hereinafter, with reference to the drawings, embodiments of the invention will be described by taking, as an example, an assembled battery used in an electric vehicle and a buffer member for the assembled battery incorporated in the assembled battery. The invention is not limited to the individual embodiments shown below, and the form can be changed and implemented.

[0016] FIGS. 1 and 2 show the appearance and structure of the secondary battery 10 incorporated in the assembled battery. FIG. 2 is a cross-sectional view taken along the X-X cross-section of FIG. 1. FIG. 3 schematically shows the structure of the assembled battery 20 having a structure in which the secondary batteries 10 and 10 are stacked. FIG. 3 is drawn from the same direction as FIG. 2.

[0017] As shown in FIG. 3, the assembled battery 20 of the present embodiment is configured by electrically connecting a plurality of secondary batteries 10 and 10 and integrating them with each other. The assembled battery 20 is configured by stacking a plurality of flat secondary batteries 10 and 10. Although not essential, typically, the positive electrode member 13 and the negative electrode member 14 of each secondary battery are connected by a bus bar 23 to make an electrical connection. Further, buffer members 21 and 21 are arranged between the individual secondary batteries 10 and 10. The buffer member 21 may be provided with cooling grooves or the like. Further, typically, end plates 22 and 22 are provided so as to sandwich the stacked structure of these secondary batteries 10 and 10 and buffer members 21 and 21, and the stacked structure of the assembled battery 20 is maintained by tightening the end plates 22 and 22 with fastening members such as bolts and bands. Known members can be appropriately used for the bus bar 23 and the end plate 22.

[0018] The battery pack 20 can be housed in a battery case (not shown) or the like and used by being mounted on a vehicle such as a hybrid vehicle. At this time, typically, cooling air for cooling the battery pack 20 is sent using the battery case or the like, and the individual secondary batteries 10, 10 are cooled. Note that the means for cooling the battery is not limited to the air-cooling method using cooling air, and a liquid-cooling method using a coolant may also be used. Further, although not shown in FIG. 3, a member for forming a passage through which the coolant or cooling air flows along the battery may be disposed between the secondary batteries 10, 10 so as to be laminated with the buffer member 21.

[0019] The buffer member 21 will be described. FIG. 4 schematically shows the laminated structure of the buffer member 21. FIG. 4 is drawn from the same direction as FIG. 3. The buffer member 21 includes a buffer body 200 and a nonwoven fabric 1 laminated and integrated with the buffer body 200. The buffer body 200 is made of crosslinked rubber. The rubber is preferably a flame-retardant rubber. Further, the buffer body 200 is in a flat plate shape. The shape of the plate of the buffer body 200 is not particularly limited, but is typically a rectangular shape similar to that of the plate-shaped secondary battery 10.

[0020] The buffer body 200 may be a solid rubber sheet or rubber plate. Further, grooves or protrusions may be provided on the surface of the buffer body 200. Further, holes or pipelines may be provided inside the buffer body 200, or the buffer body 200 may be formed in a flat bag shape.

[0021] In the embodiment of FIG. 4, the nonwoven fabric 1 is laminated and integrated on both surfaces of the flat buffer body 200 to form the buffer member 21. If necessary, the nonwoven fabric 1 may be laminated and integrated on only one side of the buffer body 200. Further, the means of integration is not particularly limited, and it is sufficient that the buffer body 200 and the nonwoven fabric 1 are integrated to the extent that they do not separate when the buffer member 21 is incorporated into the battery pack. For example, the integration may be integration using an adhesive, an adhesive agent, a double-sided tape, etc., or integration by directly forming the nonwoven fabric 1 on the surface of the buffer body 200. The buffer body 200 may be put into a nonwoven fabric formed in a bag shape and the two may be integrated.

[0022] In the form of the laminate of the buffer body 200 and the non-woven fabric 1, it is sufficient that the non-woven fabric 1 is disposed at a portion where the secondary battery 10 and the buffer body 200 face each other and press against each other. That is, it is sufficient that the non-woven fabric 1 is disposed so as to block the space between the buffer body 200 and the secondary battery 10. As long as this is the case, there may be a portion of the buffer body 200 that is not covered with the non-woven fabric 1, or there may be a portion where the non-woven fabric 1 protrudes from the buffer body 200.

[0023] In the embodiment of FIG. 10, the buffer member 28 is configured by integrating the non-woven fabric 1 on one side of the buffer body 200. Further, in this embodiment, an aluminum glass cloth 203 is disposed between the non-woven fabric 1 and the buffer body 200. The aluminum glass cloth is a material obtained by laminating and integrating a woven cloth made of glass fibers and an aluminum foil. The aluminum foil may be formed by vapor deposition or the like.

[0024] Further, in the embodiment of FIG. 11, the buffer body 201 is housed in the bag-shaped non-woven fabric 1 and fixed with an adhesive or the like as necessary to constitute a buffer member 29 in which the non-woven fabric 1 is integrated on both sides of the buffer body 201. When the non-woven fabric 1 is bag-shaped, it is easy to integrate, and it is preferable because it is easy to control the direction in which gas or flame propagates when gas or flame jets out from the battery housed in the bag. Further, in the embodiment of FIG. 11, the buffer body 201 is a hollow bag shape, and liquid or gas can be put in and out of the buffer body 201 through the joint 202 and can be used for pressurization or cooling.

[0025] The non-woven fabric 1 included in the buffer members 21, 28, and 29 will be described in detail below. The non-woven fabric 1 carries refractory functional particles 4, 4 having thermal expansibility. The functional particles 4, 4 having thermal expansibility expand when heated, improving the heat insulation property of the non-woven fabric 1. Further, the functional particles 4, 4 are refractory and do not burn out within a predetermined time even when exposed to a high temperature such as a flame. The expansion start temperature at which the functional particles 4, 4 start to expand is set higher than the temperature during normal operation of the secondary battery 10. When the secondary battery is operating normally, the functional particles 4, 4 do not expand, and are set to expand when the non-woven fabric 1 is exposed to a high temperature due to abnormal overheating of the secondary battery or occurrence of a fire. For example, the preferable range of the expansion start temperature of the refractory functional particles 4, 4 having thermal expansibility can be set to 250°C to 400°C.

[0026] Further, it is preferable that the non-woven fabric 1 is permeable to gas or liquid. For example, when the non-woven fabric 1 is disposed facing a location through which cooling air passes, the non-woven fabric 1 is preferably configured to be permeable to air.

[0027] Examples of the functional particles 4, 4 having thermal expansibility include thermally expandable graphite and aluminum phosphite. The functional particles 4, 4 are inorganic particles that do not melt even when exposed to a high temperature and maintain their function as a refractory heat insulation layer over a predetermined time (for example, 10 minutes to 30 minutes).

[0028] The form in which the non-woven fabric 1 used for the buffer member 21 carries the thermally expandable functional particles 4, 4 is not particularly limited, and the functional particles may be carried on the fibers constituting the non-woven fabric by a binder or the like. Preferably, as in the non-woven fabric 1 of the embodiment shown in FIG. 5, the thermally expandable functional particles 4, 4 are carried so as to be integrated with the long fibers made of synthetic resin. When integrated in such a form, it becomes difficult for the functional particles to fall off, and even when a large amount of functional particles are carried, air and liquid easily pass through the non-woven fabric. Hereinafter, the structure of the non-woven fabric 1 of the embodiment shown in FIG. 5 will be described in detail.

[0029] The nonwoven fabric 1 of the embodiment shown in FIG. 5 is a nonwoven fabric containing long fibers made of a synthetic resin in which functional particles 4, 4 having thermal expansibility are integrated. Here, the long fibers are long fibers contrasted with short fibers among the fibers constituting 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, whereas long fibers are fibers that are not cut short. Long fibers are typically spun by the meltblowing method, the electrospinning method, or the spunbond method and are stacked as they are to form a nonwoven fabric. Note that the nonwoven fabric 1 does not necessarily have to be composed only of long fibers, and may contain short fibers, or may be blended so that long fibers and short fibers are intertwined.

[0030] Although not essential, preferably, the blending amount of the functional particles 4, 4 with respect to the nonwoven fabric 1 is about 10 to 500 g per square meter.

[0031] Also, the nonwoven fabric may be a single layer, or may be a laminated nonwoven fabric in which a plurality of nonwoven fabric layers, films, sheets, woven fabrics, etc. are laminated. Further, the nonwoven fabric may be a composite nonwoven fabric in which a layer in which long fibers are formed into a nonwoven fabric is laminated on a woven fabric or a mesh material. The long fibers made of a synthetic resin in which the functional particles 4, 4 are integrated may be contained only in any one of the nonwoven fabric layers. Preferably, as in the embodiment of FIG. 10, an aluminum glass cloth 203 and a nonwoven fabric or a composite nonwoven fabric including the layer in which the above long fibers are formed into a nonwoven fabric may be laminated. The laminate of the aluminum glass cloth and the nonwoven fabric 1 is excellent in fire resistance and heat insulation, and the nonwoven fabric becomes stronger and easier to handle.

[0032] Also, all of the long fibers contained in the nonwoven fabric 1 may be long fibers made of a synthetic resin in which functional particles are integrated, but the nonwoven fabric 1 may contain other long fibers, for example, long fibers in which functional particles are not integrated. Although not essential, the nonwoven fabric 1 of this embodiment is a single-layer nonwoven fabric in which long fibers made of a synthetic resin in which functional particles are integrated are formed into a nonwoven fabric by the electrospinning method.

[0033] FIG. 5 schematically shows the structure of the nonwoven fabric 1 that can be used for the buffer member 21 of the assembled battery of the first embodiment. FIG. 7 is a micrograph 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 such that a plurality of large-diameter portions 2, 2 and small-diameter portions 3, 3 are arranged alternately. So to speak, the long fibers are configured such that the large-diameter portions 2, 2 and the small-diameter portions 3, 3 are strung together like beads. That is, the long fibers have diameters that change in the longitudinal direction of the fibers.

[0034] The small-diameter portions 3, 3 of the long fibers are monofilaments formed of the synthetic resin. The synthetic resin is not particularly limited as long as it can be fiberized, but it is preferably a synthetic resin suitable for the production of long fibers by the meltblowing method or the electrospinning method. Further, the synthetic resin is preferably a resin that adheres to the functional particles described later. Preferably, as the synthetic resin that serves as the raw material of the long fibers, for example, a polyurethane resin, a vinyl chloride resin, or the like can be used.

[0035] The monofilaments that become the small-diameter portions 3, 3 may be composed only of the above-described synthetic resin, but may contain other compounding materials, for example, particles having a diameter smaller than the diameter of the small-diameter portion such as a reinforcing material or a bulking agent, or a chemical agent that improves the properties of the synthetic resin.

[0036] 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 extending direction of the fiber, and a micrograph of the nonwoven fabric 1 is taken, and the fiber diameter of the small-diameter portion is measured on the photograph to obtain it. Preferably, the fiber diameter is measured at 10 to 20 small-diameter portions, and the average thereof is treated as the fiber diameter of the small-diameter portion.

[0037] The large-diameter portions 2, 2 contain thermally expandable functional particles 4, 4. Although not essential, at least a part of the large-diameter portions 2, 2 is formed by a plurality of the functional particles 4, 4 being solidified in a string-like or dumpling-like shape by the synthetic resin. Here, the string-like shape means, with respect to the shape of the large-diameter portion, that the length in the extending direction of the fiber is larger than the length in the direction orthogonal to the extending direction of the fiber, preferably 3 times or more. Also, the dumpling-like shape means, with respect to the shape of the large-diameter portion, that the length in the extending direction of the fiber is about the same as the length in the direction orthogonal to the extending direction of the fiber, preferably 1 / 2 or more and 2 times or less. Note that there may be large-diameter portions that do not contain functional particles or large-diameter portions that contain only one functional particle in the long fibers.

[0038] The diameter of the large-diameter portions 2, 2 is larger than the fiber diameter of the small-diameter portions 3, 3. The diameter of the large-diameter portion is the diameter measured in the direction orthogonal to the extending direction of the fiber. Preferably, the diameter is measured at 10 to 20 large-diameter portions and the average of them is treated as the diameter of the large-diameter portion. Although not essential, preferably, the diameter of the large-diameter portions 2, 2 is 150 nanometers or more and 300 micrometers or less. Particularly preferably, the diameter of the large-diameter portions 2, 2 is 1 micrometer or more and 50 micrometers or less. Also, preferably, the diameter of the large-diameter portions 2, 2 is 3 to 20 times the fiber diameter of the small-diameter portions 3, 3, and particularly preferably, 4 to 10 times.

[0039] Fig. 6 schematically shows the structures of the large-diameter portions 2, 2 and the small-diameter portions 3, 3 in the long fibers. The large-diameter portions 2 contain a plurality of thermally expandable functional particles 4, 4. In the illustrated form, these functional particles 4, 4 are wrapped or adhered by the same synthetic resin that constitutes the small-diameter portion, and are solidified in a string shape or a dumpling shape. In the large-diameter portions 2, 2, the functional particles 4, 4 may be adhered to each other by the synthetic resin, or the functional particles 4, 4 may be wrapped by the synthetic resin in a film shape or a net shape. In the large-diameter portions 2, 2, only one functional particle may exist in the radial direction of the fiber, or a plurality of functional particles may exist in the radial direction of the fiber. At the ends of the large-diameter portions 2, 2, the large-diameter portions 2 and the small-diameter portions 3 are continuous so that the synthetic resin contained in the large-diameter portion directly becomes the monofilament of the small-diameter portion 3, 3.

[0040] The functional particles 4, 4 contained in the large-diameter portions 2, 2 have thermal expansibility and fire resistance. That is, in the nonwoven fabric 1 of the present embodiment, particles having thermal expansibility are used as functional particles. Examples of the particles having thermal expansibility include thermally expandable microcapsules, thermally expandable graphite, and aluminum phosphite. Examples of the particles of aluminum phosphite having thermal expansibility include "APA-100" of Taihei Chemical Industry Co., Ltd. Among the aluminum phosphite particles, in particular, aluminum hydrogen phosphite particles (such as "NSF" of Taihei Chemical Industry Co., Ltd.) can be preferably used. These particles have the property of expanding when heated to a predetermined temperature. When the large-diameter portions 2, 2 contain particles having thermal expansibility, when the nonwoven fabric is heated, the large-diameter portions 2, 2 expand and change to reduce and narrow the void portions of the nonwoven fabric, resulting in a change in which the air permeability of the nonwoven fabric decreases. Further, when the functional particles 4, 4 expand, the particles themselves become a hollow structure with foaming, making it difficult for heat to pass through, and improving the heat insulation property of the nonwoven fabric 1.

[0041] Preferably, the fiber diameter Ds of the small-diameter portions 3, 3 is equal to or less than the diameter Dp of the functional particles 4, 4 included in the large-diameter portions 2, 2. The fiber diameter Ds of the small-diameter portions 3, 3 and the diameter Dp of the functional particles 4, 4 may be substantially the same. Note that the diameter Dp of the functional particles 4, 4 in the present invention refers to the volume average diameter. The diameter Dp of the functional particles 4, 4 included in the large-diameter portion is typically 300 nanometers or more and 200 micrometers or less. Also, although not essential, preferably, the fiber diameter Ds of the small-diameter portions 3, 3 is 1 / 100 or more of the diameter Dp of the functional particles 4, 4.

[0042] An example of the 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.

[0043] First, as a first step, a liquefied synthetic resin and thermally expandable functional particles are mixed. The synthetic resin is liquefied by heating and melting 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 in advance into the synthetic resin, heated and melted to obtain a liquid synthetic resin in which the functional particles are dispersed, or the synthetic resin may be dissolved in a solvent or the like to be liquefied and then the functional particles are mixed and dispersed.

[0044] In the present embodiment, a polyurethane resin was dissolved in a solvent to be liquefied, and aluminum hydrogen phosphite powder (manufactured by Taihei Chemical Industry Co., Ltd., NSF, volume average diameter 5 micrometers) as the functional particles 4, 4 was mixed therein and stirred to be dispersed.

[0045] Next, as a 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 the meltblowing method or the electrospinning method and deposited to form a nonwoven fabric.

[0046] The liquid synthetic resin sent out from the spinning nozzle is stretched by centrifugal force, gravity, electrostatic force, etc. to become thin fibrous. This thin fiber becomes the small-diameter part 3, 3 of the long fiber. At this time, when the functional particles 4, 4 are sent out from the nozzle together with the liquid synthetic resin, the part where the functional particles 4, 4 gather solidifies into a string shape or a dumpling shape to become the large-diameter part 2, 2, while the surplus synthetic resin is stretched to form the small-diameter part 3, 3, and long fibers in which the large-diameter part 2, 2 and the small-diameter part 3, 3 are alternately connected in a string are continuously formed. The formed long fibers are deposited on the base of the spinning device while solidifying as the solvent volatilizes or the temperature drops, and the non-woven fabric 1 is manufactured.

[0047] Although not essential, the second step may be performed using a rubber sheet or a rubber plate that becomes the buffer body 200 as a base material, and the non-woven fabric 1 may be directly formed on the surface of the buffer body 200 and integrated with the buffer body 200. In this way, the process of integrating the buffer body 200 and the non-woven fabric 1 can be omitted, and the non-woven fabric 1 is easy to handle. When forming the non-woven fabric 1 by electrospinning on the rubber material that becomes the buffer body 200, it is preferable to adjust the conductivity of the rubber material itself or adjust the chargeability by spray treatment or the like.

[0048] (Examples of non-woven fabrics) In the example, "NSF" (average particle diameter 5 micrometers) which is aluminum hydrogen phosphite was used as the functional particle, and the non-woven fabric 1 was obtained in which the diameter of the large-diameter part 2, 2 was approximately 2 to 10 micrometers (average diameter 6 micrometers), and the diameter of the small-diameter part 3, 3 was approximately 0.5 to 1.5 micrometers (average diameter 0.9 micrometers). The compounding amount of the functional particles 4, 4 with respect to the obtained non-woven fabric 1 was approximately 100 g / square meter. If a large number of long fibers are laminated, the compounding amount of the functional particles 4, 4 per unit area in the non-woven fabric 1 can also be increased. In addition, Fig. 7 shows a microscopic photograph of the non-woven fabric of the example. In Fig. 7, only a very small part of the layer in the thickness direction of the non-woven fabric is photographed so that the fiber form can be clearly seen. The same applies to Figs. 8 and 9.

[0049] By adjusting the blending amount of the functional particles, the viscosity and feeding rate of the liquid synthetic resin, the nozzle diameter, the applied voltage of the static electricity, the distance from the nozzle to the base, the ambient temperature, etc., the sizes, lengths, diameters, and the ratio between the large-diameter portions 2, 2 and the small-diameter portions 3, 3 can be adjusted.

[0050] When manufacturing the nonwoven fabric 1 using the melt blowing method or the electrospinning method, when spinning, since the synthetic resin is sucked out from the portion that becomes the large-diameter portion to the portion that becomes the small-diameter portion, the synthetic resin remaining in the large-diameter portion decreases. As a result, the coating film of the synthetic resin covering the functional resin in the large-diameter portion becomes thinner or net-like. By the coating film of the synthetic resin becoming thinner or net-like, the thermal expansibility of the functional particles is more quickly and effectively exhibited, which is preferable.

[0051] The secondary battery 10 will be described. As shown in FIGS. 1 and 2, the secondary battery 10 is configured such that the electrode body 11 is enclosed in a container 12 together with an electrolyte (not shown). The electrode body 11 serves as one power generation unit. As in this embodiment, one electrode body 11 may be accommodated in the container 12, or a plurality of electrode bodies 11, 11 may be accommodated in the container 12. The secondary battery 10 may also be called a single battery or a battery element in comparison with the assembled battery 20. The shape of the secondary battery 10 is not particularly limited, and it may be cylindrical, but preferably, it is flat plate-shaped as in this embodiment. The flat plate-shaped secondary battery may also be called a square battery.

[0052] As the electrode body 11, electrolyte, container 12, positive electrode member 13, and negative electrode member 14 in the secondary battery 10, known materials can be appropriately used. These members can be assembled into the secondary battery 10 by known methods.

[0053] 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 separator is sandwiched between the positive electrode and the negative electrode and is stacked and wound in a stacked state to form the electrode body 11. In this embodiment, it is a flat (flat plate-shaped) electrode body.

[0054] Known materials can be appropriately used for the positive electrode, negative electrode, and separator. The positive electrode is conductive and contains a positive electrode active material (e.g., a lithium transition metal composite oxide). The negative electrode is conductive and contains a negative electrode active material (e.g., graphite). The separator may be a porous resin film.

[0055] 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).

[0056] The container 12 is not particularly limited as long as it can enclose the electrode body 11 and the electrolyte. The container 12 may be made of resin or metal.

[0057] The positive electrode of the electrode body 11 is connected to the positive electrode member 13, and the positive electrode member 13 is exposed outside 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 outside the container 12. The positive electrode member 13 and the negative electrode member 14 serve as external terminals of the secondary battery 10 and are electrically connected to a bus bar 23 or the like.

[0058] When manufacturing the assembled battery 20 by assembling the secondary batteries 10, 10 and the buffer members 21, 21, the two are alternately laminated to obtain an assembled battery 20 having a laminated structure as shown in FIG. 3. At this time, the buffer members 21, 21 are disposed between adjacent secondary batteries 10, 10 so that the non-woven fabric 1 blocks the space between the buffer body 200 and the secondary battery 10. Further, when the buffer member 21 contains the aluminum glass cloth 203, the aluminum glass cloth 203 is disposed between the non-woven fabric 1 and the buffer body 200.

[0059] The action and effect of the buffer member 21 provided with the non-woven fabric 1 will be described. The nonwoven fabric 1 used for the buffer member 21 of the above embodiment carries heat-expandable refractory functional particles, and is a refractory nonwoven fabric in which the functional particles expand upon heating to improve the heat insulation property of the nonwoven fabric. That is, the heat insulation property of the nonwoven fabric 1 is improved when abnormal overheating or ignition occurs in the battery as compared with the normal operation of the battery. Therefore, when abnormal overheating such as ignition occurs in the secondary battery 10 of the above embodiment, the functional particles expand by heating to improve the heat insulation property of the nonwoven fabric and increase, and the nonwoven fabric itself becomes refractory and maintains its form, so that a buffer member for a laminated battery excellent in heat insulation property and fire resistance can be obtained. In addition, in a laminated battery in which such a buffer member for a laminated battery is disposed between secondary batteries, even if abnormal overheating or ignition occurs in a part of the secondary batteries, the spread or abnormal overheating of other secondary batteries is suppressed.

[0060] In particular, since such a nonwoven fabric 1 is laminated with a rubber buffer body that is crosslinked, it becomes particularly excellent in heat insulation property and fire resistance. The crosslinked rubber buffer body 200 does not melt and disappear even when heated, so it is difficult to immediately lose its shape and function as a plate-shaped buffer body even when exposed to abnormal overheating or flames. Therefore, even when the nonwoven fabric is exposed to flames or gas jets, the buffer body 200 supports / backs up the nonwoven fabric 1, and the nonwoven fabric 1 having fire resistance and heat insulation property surely exists between adjacent batteries, effectively suppressing the chain and spread of abnormal overheating of the batteries.

[0061] Furthermore, when the nonwoven fabric 1 used for the buffer member 21 contains synthetic resin long fibers in which the functional particles 4, 4 are integrated, and the long fibers have a diameter that changes in the longitudinal direction of the fiber as if a plurality of large-diameter portions 2, 2 and small-diameter portions 3, 3 are arranged alternately in a string-of-beads manner, and the small-diameter portions 3, 3 are monofilaments formed of the synthetic resin, and the large-diameter portions 2, 2 contain the functional particles 4, 4, a large amount of functional particles can be carried on the nonwoven fabric, and the fire resistance is further enhanced. Also, the functional particles are less likely to fall off from the nonwoven fabric, and the functional particles are less likely to contaminate the surroundings.

[0062] Furthermore, the fiber diameter of the small-diameter portions 3, 3 of the long fibers is equal to or less than the diameter of the functional particles 4, 4 included in the large-diameter portions 2, 2, and when the functional particles 4, 4 are wrapped by a synthetic resin in the form of a film, net, or fiber bundle, or adhered by a synthetic resin and integrated into the large-diameter portions 2, 2, the synthetic resin covering the functional particles is extremely thin, so that the thermal expansion and heat insulation properties of the functional particles are rapidly improved, and the fire resistance and anti-burning properties are further enhanced.

[0063] Furthermore, when the functional particles are particles of aluminum hydrogen phosphite, when heated, the non-woven fabric 1 changes into a heat-insulating layer with fire resistance and insulation properties due to the expanded functional particles, and the anti-burning property is further enhanced. If the functional particles are insulating, there is no risk of short-circuiting between the positive and negative electrodes of the battery with the expanded functional particles, which is preferable. Also, if the functional particles are particles of aluminum hydrogen phosphite, even when exposed to the high temperature during a battery fire, the particles with fire resistance can surely maintain the expanded form, and the fire resistance and anti-burning properties are more surely improved.

[0064] Furthermore, when the buffer member includes the alumina glass cloth 203 and the alumina glass cloth 203 is disposed between the non-woven fabric 1 and the buffer body 200, the fire resistance and anti-burning properties are more surely improved. The alumina glass cloth itself is easily burned out when exposed to a flame or the like. However, when the non-woven fabric 1 is provided on the side of the flame, the amount of heat reaching the alumina glass cloth is reduced due to the fire resistance and heat insulation properties exhibited by the non-woven fabric 1, making it difficult for the alumina glass cloth to burn out. Also, the alumina glass cloth serves as a backup material for the non-woven fabric 1, and even when the non-woven fabric 1 is exposed to the ejection of a flame or gas, the non-woven fabric 1 is less likely to collapse / disperse, and the fire resistance and heat insulation properties of the buffer member are maintained at a high level.

[0065] Also, even when the nonwoven fabric 1 is thin and easily torn, if the nonwoven fabric 1 described above is formed by the electrospinning method using the aluminum glass cloth 203 as a base material and the two are laminated and integrated, the nonwoven fabric 1 will be less likely to tear, making it easier to handle during the assembly of the buffer member or the assembled battery. From the viewpoints 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 the nonwoven fabric 1, aluminum foil, and glass cloth from the side facing the battery.

[0066] Further, if an assembled battery in which plate-shaped secondary batteries are laminated is configured such that the buffer member 21 is disposed between adjacent secondary batteries 10, 10 so that the nonwoven fabric 1 blocks the space between the buffer body 200 and the secondary battery 10, when the secondary battery experiences abnormal overheating or ignition, the nonwoven fabric 1 can exhibit fire resistance and heat insulation to suppress the ablation of the buffer body, and the thermal runaway and abnormal overheating of other secondary batteries 10, 10 can be suppressed.

[0067] Also, if the nonwoven fabric 1 is directly formed on the surface of the buffer body 200 by the melt blowing method or the electrospinning method to be integrated with the buffer body, a buffer member 21 with excellent fire resistance and heat insulation can be efficiently manufactured. Further, when the nonwoven fabric 1 is integrated with the buffer body 200, the nonwoven fabric 1 is less likely to tear during battery assembly, improving the handleability.

[0068] The invention is not limited to the above-described embodiments and can be implemented with various modifications. Other embodiments of the invention will be described below. In the following description, the focus will be on the parts that are different from the above-described embodiments, and the detailed description of the same parts will be omitted. Also, these embodiments can be implemented by combining a part of them with each other or by replacing a part of them.

[0069] As forms in which the nonwoven fabric 1 is attached to the buffer body 200, forms of attaching to one side or both sides of a plate-shaped buffer body and forms of making it into a bag shape are exemplified, but the forms are not limited to these. For example, with respect to the flat plate-shaped buffer body 200, the nonwoven fabric 1 may be attached to the buffer body 200 in a form of being bent into a U shape so as to cover two surfaces corresponding to both surfaces of the flat plate. Alternatively, the nonwoven fabric 1 may be attached so as to be wound around the buffer body 200.

[0070] The technical field in which the secondary battery 10 is used is not particularly limited. It can also be applied to other technical fields other than those exemplified in the above embodiments. For example, the secondary battery 10 can be used in electric vehicles and hybrid vehicles, but the uses of the battery and the battery pack are not limited to automotive use. For example, the secondary battery can also be used in electric bicycles. The secondary battery or the battery pack may be used as the power source for trains, ships, and aircraft. Also, the secondary battery or the battery pack may be used for the backup power source of a computer, the auxiliary storage battery of a wind power generation device or a solar power generation device, the auxiliary power source or backup power source of an industrial device, etc. Also, the secondary battery may be, for example, a lithium-ion battery, or may be an all-solid-state battery.

[0071] Also, for example, in the description of the above embodiment, it was described that the long fibers in the nonwoven fabric 1 are simply in contact with each other at the entangled portion, but the long fibers may be bonded to each other at the entangled portion. For example, at the site where the long fibers are entangled, the large-diameter portions 2, 2 may be in a state of being stuck together, or apparently, three or more (preferably four or more) small-diameter portions 3, 3 may be connected to one large-diameter portion. With such a structure, the small-diameter portions 3, 3 connect the large-diameter portions 2, 2 in a network shape, and it becomes easier to maintain the three-dimensional structure of the nonwoven fabric 1, and the air permeability is also good.

[0072] Other examples of the nonwoven fabric 1 manufactured by changing the manufacturing conditions, etc. are shown below. (Example 2 of nonwoven fabric) Figure 8 is a micrograph showing the structure of the nonwoven fabric of Example 2 manufactured by changing the manufacturing conditions and the like. Compared with the above-described examples, the manufacturing conditions were adjusted so that the long fibers became thicker as a whole. The point that the synthetic resin is a thermoplastic polyurethane resin (TPU), the point that the functional particles are "NSF" (average particle diameter: 5 micrometers), and the point that it is manufactured by the electrospinning method are the same as those of the above-described examples.

[0073] In the nonwoven fabric of Example 2, the diameter of the large-diameter portion 2,2 was approximately 2 to 15 micrometers (average diameter: 8 micrometers), and the diameter of the small-diameter portion 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 was also a portion where three or more small-diameter portions branched out from the large-diameter portion.

[0074] (Example 3 of nonwoven fabric) Figure 9 is a micrograph showing the structure of the nonwoven fabric of Example 3 manufactured by changing the manufacturing conditions and the like. Compared with the above-described examples, the manufacturing conditions were adjusted after reducing the blending amount of the functional particles. The point that the synthetic resin is a thermoplastic polyurethane resin (TPU), the point that the functional particles are "NSF" (average particle diameter: 5 micrometers), and the point that it is manufactured by the electrospinning method are the same as those of the above-described examples.

[0075] In the nonwoven fabric of Example 3, the diameter of the large-diameter portion 2,2 was approximately 3 to 8 micrometers (average diameter: 5 micrometers), and the diameter of the small-diameter portion 3,3 was approximately 0.3 to 1.0 micrometer (average diameter: 0.6 micrometer). In addition, in the nonwoven fabric of Example 3, there was also a portion where three or more small-diameter portions branched out from the large-diameter portion.

[0076] The nonwoven fabrics of the examples, Example 2, and Example 3 all had appropriate air permeability, and when exposed to hot air (about 800°C), the functional particles expanded to form a fire-resistant heat-insulating layer with almost no air permeability, improving the heat insulation performance.

[0077] In the description of the above embodiment, a single-layer nonwoven fabric containing thermally expandable functional particles was exemplified. However, the nonwoven fabric may be a multi-layer nonwoven fabric having a layer that does not contain functional particles. For example, a mesh material made of aramid fibers may be laminated on the above nonwoven fabric as a support layer to form a two-layer nonwoven fabric.

[0078] The support layer is effective for enhancing the mechanical properties of the nonwoven fabric layer containing the thermally expandable particles. In particular, if the support layer is composed of fibers made of a material with higher heat resistance than the synthetic resin, which is a material for long fibers of the nonwoven fabric, such as aramid fibers or metal fibers, when the functional particles expand due to exposure to high temperatures, it is possible to suppress the easy release of the restraint of the functional particles by the long fibers. When providing the support layer, it is particularly preferable to provide the support layer on the side of the nonwoven fabric 1 opposite to the secondary battery.

[0079] In the description of the above embodiment, it was explained that the functional particles have thermal expandability and fire resistance. However, the functions of the functional particles are not limited to thermal expandability. For example, in addition to thermal expandability, the functional particles may be particles having water retention and water absorption properties. In this case, it is also possible to increase the water absorption of the nonwoven fabric or to produce a cooling effect by vaporizing the absorbed water.

Industrial Applicability

[0080] The buffer member for the assembled battery in the above embodiment is incorporated into an assembled battery used for the power source of an electric vehicle, etc., and can suppress the thermal runaway of the battery, and has high industrial utility value.

Explanation of Symbols

[0081] 1 Nonwoven fabric 2 Large-diameter part 3 Small-diameter part 4 Functional particles 10 Secondary battery 11 Electrode body 12 Container 13 Positive electrode member 14 Negative electrode member 20 Assembled battery 21 Buffer member 200 buffer 203 aluminum glass cloth 22 end plate

Claims

1. In a battery pack in which plate-shaped secondary batteries are stacked, a buffer member for the battery pack disposed between adjacent secondary batteries, The buffer member includes a crosslinked rubber flat buffer body and a nonwoven fabric laminated and integrated with the buffer body, The nonwoven fabric carries heat-expandable refractory functional particles, and the functional particles expand upon heating to improve the heat insulation of the nonwoven fabric. Buffer member for battery pack.

2. The nonwoven fabric, Includes synthetic resin long fibers integrated with the functional particles, The long fibers have a varying diameter in the longitudinal direction of the fiber, arranged such that a plurality of large-diameter portions and small-diameter portions alternate and are connected like a string of beads, The small-diameter portion is a monofilament formed of the synthetic resin, The large-diameter portion contains the functional particles. The buffer member for battery pack according to claim 1.

3. 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, The functional particles are wrapped by the synthetic resin formed in a film shape, net shape, or bundle of fibers, or adhered by the synthetic resin and integrated with the large-diameter portion. The buffer member for battery pack according to claim 2.

4. The functional particles are particles of aluminum hydrogen phosphite The buffer member for battery pack according to claim 1

5. Furthermore, the buffer member includes an alumina glass cloth, An alumina glass cloth is disposed between the nonwoven fabric and the buffer body. The buffer member for battery pack according to any one of claims 1 to 4.

6. A battery pack in which plate-shaped secondary batteries are stacked, Between adjacent secondary batteries, the buffer member for battery pack according to any one of claims 1 to 4 is disposed such that the nonwoven fabric blocks the space between the buffer body and the secondary battery. Battery pack.

7. A method for manufacturing the buffer member for battery pack according to claim 2, A first step of heating the synthetic resin to melt or dissolve it with a solvent to liquefy it, and dispersing the functional particles in the liquefied synthetic resin, Subsequent to the first step, a second step of spinning the liquid synthetic resin in which the functional particles are dispersed by the melt blowing method or the electrospinning method to form a long fiber and at the same time form a nonwoven fabric, In the second step, the nonwoven fabric is directly formed on the surface of the buffer body and integrated with the buffer body. Method for manufacturing a buffer member for battery pack.

Images