Fire spread prevention material, battery pack, and automobile

Abstract

To provide a fire spread prevention material capable of sufficient fire spread prevention, a battery pack utilizing the fire spread prevention material, and an automobile comprising the battery pack.SOLUTION: One aspect of the present invention provides a fire spread prevention material. The fire spread prevention material comprises an inorganic fiber base material which contains inorganic fibers, and sodium silicate which is supported on the inorganic fiber base material. The sodium silicate has a water content from 15 mass% to 35 mass% inclusive at 100°C.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fire prevention material, a battery pack, and an automobile. [Background technology]

[0002] As the electrification of automobiles becomes more widespread, the development of automotive battery packs and the battery cells used in them is progressing. Among automotive battery packs, those using lithium-ion battery (LiB) cells, which have high energy density, are particularly at risk of abnormalities such as thermal runaway. For this reason, technology to improve the safety of battery cells is being developed. For example, Patent Document 1 proposes a heat absorbing sheet that is used for the purpose of avoiding a sudden temperature rise and a thermal runaway state (heat escape) caused by an internal short circuit in a lithium ion battery, etc. However, such a heat absorbing sheet does not necessarily have sufficient fire spread prevention properties. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2010-53196 A Summary of the Invention [Problem to be solved by the invention]

[0004] In view of the above circumstances, the present invention provides a fire prevention material having sufficient fire spread prevention properties, a battery pack using this fire prevention material, and a vehicle equipped with this battery pack. [Means for solving the problem]

[0005] According to one aspect of the present invention, there is provided a fire spread prevention material. The fire spread prevention material includes an inorganic fiber substrate containing inorganic fibers and sodium silicate supported on the inorganic fiber substrate. The sodium silicate has a moisture content of 15% by mass or more and 35% by mass or less at 100°C.

[0006] According to this embodiment, sufficient fire spread prevention properties can be exhibited. [Brief description of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing the state of water molecules present in sodium silicate. [Diagram 2] FIG. 2 is a cross-sectional view showing a schematic diagram of an embodiment of the fire prevention material. [Diagram 3] FIG. 3 is a cross-sectional view showing a schematic diagram of an embodiment of the fire prevention material. [Figure 4] Fig. 4(a) is a plan view showing an embodiment of a fire prevention material having an exterior body, and Fig. 4(b) is a side view showing an embodiment of a fire prevention material having an exterior body and an enlarged view showing a cross section of an end portion. [Diagram 5] FIG. 5 is a graph showing the change in moisture content (rate of decrease) of sodium silicate with temperature change. [Figure 6] FIG. 6 is a schematic diagram showing the configuration of a battery cell assembly for a simulated combustion test. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Various features shown in the following embodiments can be combined with each other. In this specification, the content of Y in X means the proportion (mass%) of Y based on the total mass of X, and the water content of sodium silicate means the proportion (mass%) of water based on the total mass of sodium silicate. Fig. 1 is a schematic diagram showing the state of water molecules present in sodium silicate, Fig. 2 and Fig. 3 are cross-sectional views each showing a typical embodiment of a fire prevention material. The fire spread prevention material of the present invention is used by being disposed between two adjacent battery cells of a battery pack having two or more battery cells. Here, the fire prevention material is required to have heat insulating properties (fire prevention properties) that suppress heat transfer to adjacent battery cells in the event of an abnormality.

[0009] The fire spread prevention material of the present invention includes an inorganic fiber substrate containing inorganic fibers and sodium silicate supported on the inorganic fiber substrate. The sodium silicate has a moisture content of 15% by mass or more and 35% by mass or less at 100°C. The sodium silicate is a compound represented by Na2O·nSiO2·mH2O (m is 0 or a positive number). In this fire prevention material, sodium silicate contains sufficient moisture even at 100°C, so that in an emergency, the latent heat of vaporization of moisture provides good insulation (insulation effect). Therefore, even if one battery cell were to catch fire in an emergency, the spread of fire to adjacent battery cells can be prevented or delayed.

[0010] In addition, the fire prevention properties of a fire prevention material can be evaluated by heating one side of the fire prevention material at 650°C for 120 seconds and measuring the surface temperature of the other side of the fire prevention material (surface temperature after 120 seconds have passed). The surface temperature of the other side of the fire spread prevention material after 120 seconds is preferably about 150° C. or less, more preferably about 140° C. or less, and even more preferably about 120° C. or less. The lower limit of the surface temperature is, for example, about 25° C. If the fire spread prevention material exhibits a surface temperature within the above range, it can be determined that the fire spread prevention property is excellent. The surface temperature can be measured by the method described in the Examples.

[0011] Furthermore, since the battery cells repeatedly expand and contract when the assembled battery is charged and discharged, it is preferable that the fire spread prevention material has flexibility that can follow the expansion and contraction of the battery cells. In this case, by combining an inorganic fiber base material carrying sodium silicate with, for example, a polyurethane sheet material, it is possible to impart good flexibility to the fire spread prevention material. This allows the fire spread prevention material to follow the expansion and contraction of the battery cells, reducing the mechanical load on the battery cells, allowing the assembled battery to repeatedly operate (charge and discharge) stably. In addition, in the fire prevention material of the present invention, sodium silicate contains a larger amount of moisture at temperatures below 100° C. Therefore, the fire prevention material can maintain high flexibility during production of the fire prevention material, storage of the fire prevention material, production of the assembled battery, etc. As a result, the productivity of the fire prevention material and the assembled battery can be improved.

[0012] The moisture content of sodium silicate at 100°C may be about 15% by mass or more and 35% by mass or less, preferably about 18% by mass or more and 32% by mass or less, and more preferably about 21% by mass or more and 29% by mass or less. In this case, the above-mentioned effect of the fire spread prevention material can be further improved. The moisture content (moisture content change) of sodium silicate can be measured (obtained) by the method described in the examples. The rate of decrease in moisture content of sodium silicate from 30°C to 100°C is preferably about 0.75% by mass / °C or less, more preferably about 0.65% by mass / °C or less, and even more preferably about 0.55% by mass / °C or less. In this case, the fire spread prevention material contains sufficient moisture in the temperature range of 30°C to 100°C, which can contribute to improving the productivity of the fire spread prevention material and the battery pack, and to stable operation of the battery pack. The rate of decrease in moisture content (% by mass / °C) can be calculated by the following formula 1. Formula 1: Moisture content reduction rate (mass% / ℃) = ([Moisture content of sodium silicate at 30℃] - [Moisture content of sodium silicate at 100℃]) / [Moisture content of sodium silicate at 30℃] × 100

[0013] Here, the state of water molecules present in sodium silicate is classified as follows, as shown in Figure 1: I: free water, II: water molecules hydrogen-bonded with OH, III: water molecules adsorbed to Na, and IV: water molecules present as OH. The order of evaporation of water molecules is thought to be I → II → III → IV (however, evaporation may occur simultaneously). For this reason, from the viewpoint of increasing the moisture content of sodium silicate in a higher temperature range, it is preferable to increase the ratio of Na2O contained in sodium silicate (i.e., to decrease the SiO2 / Na2O molar ratio). Specifically, the SiO2 / Na2O molar ratio is preferably about 3.7 or less, more preferably about 1 to 3.5, even more preferably about 1.5 to 3, and particularly preferably 2 to 2.3. By using such sodium silicate, the fire prevention property of the fire prevention material is further improved, and the productivity of the fire prevention material and the battery pack can also be further increased.

[0014] The ratio of sodium silicate to the total of sodium silicate and the inorganic fiber substrate is preferably about 60% by mass or more and about 98% by mass or less, more preferably about 70% by mass or more and about 95% by mass or less, and even more preferably about 75% by mass or more and about 90% by mass or less. In this case, it is easy to impart superior fire spread prevention properties to the fire spread prevention material, and the weight of the fire spread prevention material can also be reduced. The ratio of the inorganic fiber base material to the total of sodium silicate and the inorganic fiber base material is preferably about 1% by mass to 40% by mass, more preferably about 1% by mass to 35% by mass, even more preferably about 5% by mass to 35% by mass, particularly preferably about 8% by mass to 30% by mass, and most preferably about 10% by mass to 20% by mass. In this case, it is easy to impart better fire spread prevention properties to the fire spread prevention material.

[0015] The inorganic fiber substrate is a substrate (e.g., a sheet) mainly composed of inorganic fibers. In such an inorganic fiber substrate, a plurality of voids (pores) are formed between the inorganic fibers. That is, the inorganic fiber substrate has a porous structure. For example, a layer containing sodium silicate can be formed unevenly on one side of the inorganic fiber substrate by preparing a relatively high-viscosity aqueous solution of sodium silicate, applying it to one side of the inorganic fiber substrate, and then drying it. In addition, for example, a relatively low-viscosity aqueous solution of sodium silicate can be prepared, impregnated into the inorganic fiber substrate, and then dried to fill the voids in the inorganic fiber substrate with sodium silicate.

[0016] In this specification, inorganic fibers are fibrous substances having a length of about 1 mm or more and an aspect ratio (length / width) of about 100 or more. The length (fiber length) of the inorganic fibers is preferably about 3 mm or more and 12 mm or less. The width (fiber diameter) of the inorganic fibers is preferably about 3 μm or more and 10 μm or less. When the inorganic fibers constituting the inorganic fiber substrate have the above fiber length and fiber diameter, the inorganic fiber substrate tends to have excellent shape processability before drying in the manufacturing process. From the same viewpoint, the average fiber diameter of the inorganic fibers is preferably about 5 μm or more and 10 μm. Here, the average fiber diameter is a value measured by microscope observation such as a scanning electron microscope (SEM) or an optical microscope.

[0017] The inorganic fiber substrate may be made up of one type or multiple types of inorganic fibers. Examples of materials for the inorganic fibers constituting the inorganic fiber substrate include silica (SiO2), alumina (Al2O3), carbon, silicon carbide (SiC), etc. Among these, it is preferable that the material for the inorganic fibers contains at least one selected from the group consisting of silica (SiO2) and alumina (Al2O3). In this case, the fire prevention material can be given higher fire spread prevention properties, and the inorganic fiber substrate tends to have excellent shape processability before drying in the manufacturing process. Examples of such inorganic fibers include glass fibers, silica fibers, alumina-silica fibers, alumina fibers, basalt fibers, and rock wool. Among these, it is preferable that the inorganic fiber substrate contains at least one of glass fibers, silica fibers, and alumina-silica fibers. In this case, the above-mentioned effects can be further improved.

[0018] The content of inorganic fibers in the inorganic fiber substrate is preferably about 60% by mass or more and 100% by mass or less, more preferably about 70% by mass or more and 98% by mass or less, even more preferably about 80% by mass or more and 95% by mass or less, and particularly preferably about 85% by mass or more and 93% by mass or less. In this case, the fire spread prevention material can impart excellent fire spread prevention properties. The inorganic fiber substrate may further contain an organic binder. The organic binder is, for example, an organic material that bonds the inorganic fibers together, and one type of organic binder may be used alone, or multiple types may be used in combination. As the organic binder, for example, a resin having a glass transition point below room temperature (for example, 25° C.), a water-soluble resin, etc. Specific examples of the organic binder include, for example, an acrylic resin, a polyvinyl alcohol resin (such as Vinylon), an epoxy resin, cellulose such as cellulose microfibril, a polyvinyl chloride resin, etc.

[0019] Here, the acrylic resin is a polymer containing at least one monomer unit selected from the group consisting of acrylic acid and its derivatives (such as acrylic acid esters), and methacrylic acid and its derivatives (such as methacrylic acid esters). Also, the cellulose microfibril refers to microfibrillated cellulose fibers. Among them, the organic binder preferably contains at least one selected from the group consisting of an acrylic resin, a polyvinyl alcohol resin, and an epoxy resin, which tends to provide a fire prevention material having higher fire spread prevention properties. The content of the organic binder in the inorganic fiber substrate is preferably about 0% by mass or more and about 40% by mass or less, more preferably about 2% by mass or more and about 30% by mass or less, even more preferably about 5% by mass or more and about 20% by mass or less, and particularly preferably about 7% by mass or more and about 15% by mass or less. In this case, a fire prevention material having better fire spread prevention properties is easily obtained.

[0020] The inorganic fiber substrate may further contain inorganic particles, such as silica, aluminum hydroxide, zinc oxide, magnesium carbonate, and aluminum silicate. Examples of particles containing silica include precipitated silica, fumed silica, colloidal silica, etc. Note that precipitated silica is amorphous silica particles obtained by a precipitation method, which is a type of wet method, and has a porous structure. The average particle size of the inorganic particles is preferably about 0.1 μm or more and 100 μm or less, more preferably about 0.5 μm or more and 80 μm or less, and even more preferably about 1 μm or more and 50 μm or less. Here, the average particle size of the inorganic particles is the value of the volume cumulative particle size D50 measured by a laser diffraction type particle size measuring device. Inorganic particles having such an average particle size are easy to handle and can be easily distributed more uniformly in the inorganic fiber substrate.

[0021] The content of inorganic particles in the inorganic fiber substrate is preferably about 20% by mass or more and 50% by mass or less, more preferably about 25% by mass or more and 45% by mass or less, and even more preferably about 30% by mass or more and 40% by mass or less. By containing inorganic particles at such a content, a fire prevention material having improved heat insulation and better fire prevention properties can be obtained. In addition, an inorganic fiber substrate (and thus a fire prevention material) that is lighter and has higher mechanical strength can be obtained. From the viewpoint of increasing the mechanical strength of the inorganic fiber substrate, it is preferable that the inorganic fiber substrate does not contain precipitated silica, and it is more preferable that the inorganic fiber substrate does not contain inorganic particles.

[0022] The inorganic fiber substrate may contain a flocculant such as a polyamidine polymer. The content of the flocculant in the inorganic fiber substrate is preferably about 0.1% by mass to about 5% by mass, more preferably about 0.3% by mass to about 4% by mass, and even more preferably about 0.5% by mass to about 3% by mass. The inorganic fiber substrate may contain sodium silicate (sodium silicate other than sodium silicate having a moisture content at 100° C. of 15% by mass or more and 35% by mass or less), or may not contain such sodium silicate. When such sodium silicate is contained, the content of sodium silicate in the inorganic fiber substrate is preferably about 10 mass % or less, more preferably about 5 mass % or less, and even more preferably about 3 mass % or less.

[0023] As the inorganic fiber substrate, for example, a substrate having excellent retention (support) of sodium silicate is preferably used. The inorganic fiber substrate is preferably a nonwoven fabric, more preferably a sheet (wet-formed sheet) formed by a wet-formed papermaking method. The wet-formed sheet is preferable from the viewpoint of being particularly excellent in retention of sodium silicate. In the wet papermaking method, materials (inorganic fibers, organic binders, etc.) are dispersed in water, the resulting dispersion is paper-formed on a papermaking screen, and dried to produce an inorganic fiber substrate (nonwoven fabric). This method makes it easy to obtain an inorganic fiber substrate (nonwoven fabric) having substantially uniformly distributed voids. Therefore, wet papermaking sheets tend to have substantially uniformly distributed voids and have excellent retention of sodium silicate. The apparent density of the inorganic fiber substrate is 0.08 g / cm 3 More than 0.2g / cm 3 The weight of the inorganic fiber substrate is preferably about 100 g / m2 or less when the thickness is 1 mm. 2 Below 170g / m 2 It is preferable that the temperature is about the same or less. The thickness of the inorganic fiber substrate is preferably 0.2 mm or more and 3 mm or less.

[0024] The sodium silicate may be unevenly distributed on one side of the inorganic fiber substrate, or may be impregnated into the inorganic fiber substrate. That is, the fire spread prevention material 1 may have a two-layer structure of an inorganic fiber substrate 2 and a layer 3 containing sodium silicate SS as shown in Fig. 2, or may have a single-layer structure in which the inorganic fiber substrate 2 is impregnated with sodium silicate SS as shown in Fig. 3. The two-layered fire spread prevention material 1 can be formed, for example, by preparing a relatively highly viscous aqueous solution of sodium silicate SS, applying it to one side of the inorganic fiber substrate 2, and then drying it to form a layer 3 containing sodium silicate SS unevenly distributed on one side of the inorganic fiber substrate 2. For this application, a gravure coating method, a slot die coating method, a knife coating method, a blade coating method, a comma coating method, a reverse roll coating method, an inkjet method, or the like is suitably used.

[0025] On the other hand, a single-layer fire spread prevention material 1 can be produced, for example, by preparing a relatively low viscosity aqueous solution of sodium silicate SS, impregnating it into an inorganic fiber base material 2, pressurizing it if necessary, and then drying it, thereby filling the voids in the inorganic fiber base material 2 with sodium silicate SS. Any of the above fire spread prevention materials 1 are suitably manufactured by a roll-to-roll process in which the inorganic fiber substrate 2 wound into a roll is sent out, an aqueous solution of sodium silicate SS is supplied and dried, and then the material is wound into a roll. As described above, the fire spread prevention material 1 can maintain high flexibility even during the manufacture of the fire spread prevention material 1. Therefore, the operation of winding the fire spread prevention material 1 into a roll can be performed smoothly, and cracks, etc. are unlikely to occur in the fire spread prevention material 1 even after it is wound into a roll.

[0026] In the configuration example of Fig. 2, the layer 3, and in the configuration example of Fig. 3, the fire spread prevention material 1 (hereinafter referred to as the "sodium silicate-containing portion") preferably absorb heat in the temperature range of 100°C to 300°C. In addition, when the sodium silicate-containing portion is heated from 100°C to 300°C at a rate of 50°C / min, the mass reduction rate is preferably 15% by mass or more. The endothermic reaction of the sodium silicate-containing portion is believed to occur when moisture in the sodium silicate-containing portion (e.g., water molecules in sodium silicate) undergoes an endothermic reaction in the temperature range of 100° C. to 300° C. On the other hand, the mass loss of the sodium silicate-containing portion is believed to occur due to this endothermic reaction. Therefore, the mass loss rate when the sodium silicate-containing portion is heated from 100°C to 300°C at 50°C / min correlates with the moisture content and heat absorption rate contained in the sodium silicate-containing portion. For this reason, it is presumed that when the mass loss rate of the sodium silicate-containing portion is 15% by mass or more, the heat absorption rate in the above temperature range becomes large, and sufficient fire spread prevention properties are obtained in the fire spread prevention material. The endothermic heat of the sodium silicate-containing portion can be confirmed, for example, by performing thermogravimetry-differential thermal analysis (TG-DTA) measurement and checking the presence or absence of an endothermic peak within the temperature range of 100° C. or higher and 300° C. or lower.

[0027] The mass reduction rate when the sodium silicate-containing portion is heated from 100°C to 300°C at 50°C / min is preferably about 15% by mass or more and 30% by mass or less, more preferably about 17% by mass or more and 28% by mass or less, even more preferably about 20% by mass or more and 25% by mass or less, particularly preferably about 23% by mass or more and 25% by mass or less, and most preferably about 23.5% by mass or more and 25% by mass or less. A fire prevention material having better fire prevention properties is easily obtained. The mass reduction rate can be calculated by the following formula 2. Formula 2: Mass reduction rate (mass%) = [mass reduction amount of sodium silicate-containing part] / [mass of sodium silicate-containing part at 100 ° C.] × 100 Here, the mass loss of the sodium silicate-containing portion is the difference between the mass of the sodium silicate-containing portion at 100° C. and the mass of the sodium silicate-containing portion at 300° C. When multiple sodium silicate-containing portions are present, the mass loss rate of each sodium silicate-containing portion may be in the above range, and the total mass loss rate of all the sodium silicate-containing portions may be in the above range.

[0028] It is preferable that the fire spread prevention material has insulating properties. In this case, for example, the both sides of the inorganic fiber substrate supporting sodium silicate are protected with a resin sheet material, or the inorganic fiber substrate supporting sodium silicate is housed in an exterior body 5 described below, whereby the fire spread prevention material can be given high insulating properties. Here, having insulating properties means that the electrical resistivity measured by volume resistivity measurement is 10 8 This means that the resistance is Ω·cm or more. The fire spread prevention material may be in a sheet form (for example, a flat plate form) or may be processed into a predetermined shape. The predetermined shape may be appropriately set depending on the shape of the installation location of the fire spread prevention material. The predetermined shape may be, for example, a shape that conforms to the shape of the installation location of the fire spread prevention material (such as the surface shape of the component that is placed opposite the fire spread prevention material). Specific examples of the shape include a sheet shape with unevenness on the surface, a sheet shape with a curved portion at an angle of 90° or more, etc. The shape of the unevenness (the shape of the convex and concave portions) is not particularly limited, and may be a rectangular cross section, a V-shaped cross section, a U-shaped cross section, etc. The fire spread prevention material processed into a predetermined shape can be manufactured by the manufacturing method described below, which can prevent separation and breakage between the inorganic fiber base material and the sodium silicate. The absence of separation and breakage in the fire spread prevention material can be confirmed, for example, by observing the cross section of the fire spread prevention material using a scanning electron microscope (SEM).

[0029] A fire prevention material that has been processed into a predetermined shape can maintain that shape. The ability of a fire prevention material to maintain a predetermined shape can be quantified by the three-point bending strength of the fire prevention material. Specifically, the three-point bending strength of the fire spread prevention material measured according to JIS K 7171 is preferably about 0.5 MPa to 5 MPa, more preferably about 0.8 MPa to 4 MPa, and even more preferably about 1 MPa to 3 MPa. It can be said that a fire spread prevention material with such a three-point bending strength has sufficient strength to maintain a predetermined shape. The total thickness of the inorganic fiber base material and sodium silicate (thickness of the fire spread prevention material 1 in the configuration examples of Figs. 2 and 3) is preferably about 5 mm or less, more preferably about 1 mm to 5 mm, more preferably about 1.2 mm to 4 mm, and even more preferably about 1.5 mm to 3 mm. In this case, a fire spread prevention material with higher fire spread prevention properties can be obtained, and the arrangement space for the fire spread prevention material in the battery pack can be prevented from becoming large.

[0030] As shown in Fig. 4, the fire spread prevention material 1 may further include an exterior body 5 that contains the inorganic fiber substrate 2 and sodium silicate SS. In other words, the fire spread prevention material 1 can be said to include a fire spread prevention material main body, which is the inorganic fiber substrate 2 supporting sodium silicate SS, and an exterior body 5 that contains this fire spread prevention material main body. By containing sodium silicate SS in the exterior body 5, the amount of moisture dissipated from the fire spread prevention material 1 can be adjusted (reduced). Fig. 4(a) is a plan view showing an embodiment of a fire prevention material having an exterior body, and Fig. 4(b) is a side view showing an embodiment of a fire prevention material having an exterior body and an enlarged view showing a cross section of an end portion. The water vapor transmission rate of the exterior body 5 at 40°C and 90% RH is 15g / m 2 / day or less, and 2 / day or less is more preferable, and 5 g / m 2 / day or less is more preferable, and 2 It is particularly preferable that the lower limit of the water vapor transmission rate of the exterior body at 40°C is about 0.01 g / m 2 By setting the water vapor transmission rate of the exterior body 5 within the above range, the amount of moisture dissipated from the fire spread prevention material 1 can be more reliably adjusted (reduced), thereby further improving the fire spread prevention properties. The water vapor permeability (water vapor transmission rate) is measured by a method in accordance with JIS K 7129-2:2019.

[0031] The exterior body 5 contains a composite of the inorganic fiber base material 2 and sodium silicate SS inside by sealing the outer peripheries of the two sheet materials 5a, 5b with a seal portion 50. The seal portion 50 is formed by joining the outer peripheries of the two sheet materials 5a, 5b by a method such as fusion (ultrasonic fusion, high-frequency fusion, heat fusion). Note that it is also possible to fold one sheet material in half and seal the outer periphery with a seal portion to contain a composite of the inorganic fiber base material 2 and sodium silicate SS inside. In this embodiment, each sheet material 5a, 5b is a laminate having a base layer 51, a sealing layer 52 provided on the inner surface side of the base layer 51, and a protective layer 53 provided on the outer surface side of the base layer 51.

[0032] The base layer 51 has a function of imparting mechanical strength to the sheet materials 5a and 5b, and a function of adjusting (blocking) the transmission of moisture (water vapor). The base layer 51 may be made of a metal foil. Examples of materials for the metal foil include aluminum or an aluminum alloy, nickel or a nickel alloy, and stainless steel. The thickness of the base layer 51 is not particularly limited, but is preferably about 5 μm to 100 μm, more preferably about 8 μm to 80 μm, and even more preferably about 12 μm to 60 μm. In this case, appropriate water vapor permeability and sufficient flexibility of the sheet materials 5a and 5b can be ensured.

[0033] The sealing layer 52 has a function of sealing the exterior body 5 by being fused. Examples of the constituent material (fusible material) of the sealing layer 52 include polyethylene (LDPE, LLPDE), polypropylene, ethylene-vinyl acetate copolymer, polyethylene terephthalate, polybutylene terephthalate, polyvinyl chloride, polyvinylidene chloride, ethylene-vinyl alcohol copolymer, polystyrene, polyacrylonitrile, ethylene-(meth)acrylic acid copolymer, polymethylpentene, etc. As the constituent material of the sealing layer 52, polypropylene is more preferable, and non-oriented polypropylene is further preferable. The thickness of the sealing layer 52 is not particularly limited, but is preferably about 5 μm to 200 μm, more preferably about 10 μm to 100 μm, even more preferably about 20 μm to 120 μm, and particularly preferably about 30 μm to 80 μm, which can improve the sealing performance while ensuring the flexibility of the sheet materials 5a and 5b.

[0034] The protective layer 53 has a function of protecting the base material layer 51 (preventing corrosion of the base material layer 51, etc.). A relatively hard resin material is used as the constituent material of the protective layer 53. Examples of such hard resin materials include polyamide resins (nylon), acrylic resins, polyimide resins, polyetherimide resins, polysulfone resins, polyethersulfone resins, polyetheretherketone resins, polycarbonate resins, polyvinyl butyral resins, polyarylate resins, fluorine resins, and polyester resins. The thickness of the protective layer 53 is not particularly limited, but is preferably about 5 μm or more and 100 μm or more, more preferably about 10 μm or more and 50 μm or more, and even more preferably about 15 μm or more and 30 μm or more.

[0035] The thickness of the exterior body is not particularly limited, but is preferably about 250 μm or less, more preferably about 200 μm or less, and even more preferably about 100 μm or less. In this case, it becomes easier to set the water vapor transmission rate of the exterior body 5 within the above range. As a result, the amount of moisture dissipated from the fire spread prevention material 1 can be suitably adjusted (reduced), and thus the fire spread prevention property is further improved. The sheet materials 5a and 5b are not limited to a three-layer structure, and may be a single-layer (one-layer) structure, a two-layer structure, or a four-layer or more structure, depending on the required characteristics. Although the fire spread prevention material according to one embodiment has been described above, the fire spread prevention material of the present invention is not limited to the above embodiment. As another embodiment of the present invention, there is provided a battery pack including two or more battery cells and the above-mentioned fire prevention material disposed between adjacent battery cells. This battery pack is, for example, a lithium ion battery. As another embodiment of the present invention, there is provided an automobile including an automobile body and the above-described battery pack mounted in the automobile body. Furthermore, it may be provided in the following aspects:

[0036] (1) A fire spread prevention material comprising an inorganic fiber base material containing inorganic fibers and sodium silicate supported on the inorganic fiber base material, the sodium silicate having a moisture content of 15% by mass or more and 35% by mass or less at 100°C.

[0037] (2) The fire prevention material according to (1) above, wherein the sodium silicate exhibits a rate of decrease in moisture content of 0.75 mass% / °C or less from 30°C to 100°C.

[0038] (3) The fire prevention material according to (1) or (2) above, wherein the constituent material of the inorganic fibers includes at least one selected from the group consisting of silica (SiO2) and alumina (Al2O3).

[0039] (4) The fire prevention material according to any one of the above (1) to (3), wherein the inorganic fiber base material is a wet-formed sheet.

[0040] (5) A fire prevention material according to any one of (1) to (4) above, wherein the sodium silicate is unevenly distributed on one side of the inorganic fiber base material or is impregnated into the inorganic fiber base material.

[0041] (6) The fire prevention material according to any one of the above (1) to (5), wherein the total thickness of the inorganic fiber base material and the sodium silicate is 5 mm or less.

[0042] (7) The fire prevention material according to any one of the above (1) to (6), further comprising an exterior body that houses the inorganic fiber base material and the sodium silicate.

[0043] (8) In the fire prevention material according to any one of the above (1) to (7), the exterior body has a water vapor transmission rate of 15 g / m at 40° C. and 90% RH. 2 / day or less and a thickness of 250 μm or less.

[0044] (9) The fire prevention material according to any one of (1) to (8) above, which is disposed between two adjacent battery cells of a battery pack including two or more battery cells.

[0045] (10) An assembled battery comprising: two or more battery cells; and a fire prevention material according to any one of (1) to (9) above, disposed between adjacent battery cells.

[0046] (11) An automobile comprising: an automobile body; and the battery pack according to (10) above, mounted in the automobile body. Of course, this is not the case.

[0047] Finally, although various embodiments according to the present disclosure have been described, these are presented as examples and are not intended to limit the scope of the invention. The novel embodiment can be implemented in various other forms, and various omissions, substitutions, and modifications can be made without departing from the spirit of the invention. The embodiments and their modifications are included within the scope and spirit of the invention, and are included in the scope of the invention and its equivalents described in the claims. EXAMPLES

[0048] The present invention will be described in more detail below using the following examples and comparative examples, but the present invention is not limited to the following examples.

[0049] 1. Material Preparation <Sodium silicate> SS1: SiO2 / Na2O molar ratio=2.1 SS2: SiO2 / Na2O molar ratio=3.2 SS3: SiO2 / Na2O molar ratio=3.7

[0050] <Inorganic fibers> F1: Glass fiber (average fiber diameter 10 μm) <Organic binder> B1: Vinylon fiber (average fiber diameter 5 μm)

[0051] 2. Changes in moisture content of sodium silicate and results For each of the sodium silicates SS1 to SS3, a thermogravimetric measuring device (NETZSCH Japan, "High-sensitivity differential thermobalance STA 2500 Regulus") was used to measure the mass change up to 1000°C. The measured value at 1000°C was defined as the "solid content contained in each of the sodium silicates SS1 to SS3", and the change in moisture content in each of the sodium silicates SS1 to SS3 was calculated from this solid content value and the measured value of the thermogravimetry. FIG. 5 is a graph showing the change in moisture content (rate of decrease) of sodium silicate with temperature change.

[0052] Sodium silicate SS1 had a moisture content of 55 mass% at 30°C and 26 mass% at 100°C, and the rate of decrease in moisture content from 30°C to 100°C was 0.53 mass% / °C. Sodium silicate SS2 had a moisture content of 61 mass% at 30°C and 19 mass% at 100°C, and the rate of decrease in moisture content from 30°C to 100°C was 0.69 mass% / °C. Sodium silicate SS3 had a moisture content of 61 mass% at 30°C and 13 mass% at 100°C, and the rate of decrease in moisture content from 30°C to 100°C was 0.79 mass% / °C. In this way, the order of the magnitude relationship of the moisture content of sodium silicate SS1, sodium silicate SS2 and sodium silicate SS3 was reversed between 30°C and 100°C.

[0053] 3. Preparation of inorganic fiber substrate (wet-processed sheet) 6.5 parts by mass of inorganic fiber F1 and 0.7 parts by mass of organic binder B1 were added to 100 parts by mass of pure water and mixed for 2 hours using a homomixer manufactured by Tokushu Kika Kogyo Co., Ltd. to obtain a dispersion liquid. This dispersion liquid was paper-formed on a papermaking screen and dried using a Yankee dryer to produce wet-formed sheets (nonwoven fabric) A and wet-formed sheets (nonwoven fabric) B of different thicknesses. The thickness of wet-formed sheet A is 1.5 mm, and the weight is 73 g / m 2 The thickness of the wet-formed sheet B was 1.5 mm, 2 mm, and 3 mm, and the basis weight was 120 g / m 2 It was.

[0054] 4. Preparation of fire prevention material Example 1 An aqueous solution of sodium silicate SS1 prepared to a predetermined solid content was applied to the upper surface of the wet-formed sheet (inorganic fiber substrate) A by a slot die coating method, and then dried at 30° C. In this way, a fire spread prevention material (total thickness: 3 mm) with a two-layer structure comprising a wet-formed sheet and an upper layer containing sodium silicate SS1 was produced. Example 2 A two-layer fire prevention material was produced in the same manner as in Example 1, except that sodium silicate SS1 was changed to sodium silicate SS2. Comparative Example 1 A two-layer fire prevention material was produced in the same manner as in Example 1, except that sodium silicate SS1 was changed to sodium silicate SS3.

[0055] Example 3 The aqueous solution of sodium silicate SS1 prepared to a predetermined solid content was impregnated into a wet-formed sheet (inorganic fiber substrate) B, compressed with a roller, and then dried at 30°C. As a result, a one-layer fire prevention material (total thickness: 1.5 mm, 2 mm, and 3 mm) was produced in which sodium silicate SS1 was filled into the voids of the wet-formed sheet. Example 4 A one-layer fire prevention material was produced in the same manner as in Example 3, except that sodium silicate SS1 was changed to sodium silicate SS2. Comparative Example 2 A one-layer fire prevention material was produced in the same manner as in Example 3, except that sodium silicate SS1 was changed to sodium silicate SS3.

[0056] 5. Measurement and Evaluation 5-1. Confirmation of endothermic peak First, a part of the obtained fire prevention material was taken and crushed to obtain a measurement sample. Next, the measurement sample was subjected to DTA measurement using a thermogravimetric-differential thermal analyzer (TG-DTA) to obtain a differential thermal curve when the temperature was raised from room temperature to 300°C at a rate of 10°C / min. In the obtained differential thermal curve, it was confirmed whether or not an endothermic peak was present in the temperature range from 100°C to 300°C.

[0057] 5-2. Fire prevention evaluation A 3 mm thick fire prevention material, a K thermocouple, and an aluminum block (500 g) were layered in this order on a hot plate (MSA Factory, "PA8015") heated to 650°C. The back surface temperature of the fire prevention material (the surface temperature on the side opposite the hot plate) was measured after 120 seconds had elapsed, and the fire prevention properties were evaluated according to the following criteria.

[0058] A: The back surface temperature of the fire prevention material was below 150°C. B: The back surface temperature of the fire prevention material was higher than 150°C and lower than 190°C. C: The back surface temperature of the fire prevention material was higher than 190°C. In addition, a fire prevention material was rated as having sufficient fire spread prevention properties when rated as "B" according to the above criteria, and as having excellent fire spread prevention properties when rated as "A." The results are shown in Tables 1 and 2 below.

[0059] [Table 1]

[0060] [Table 2]

[0061] Each of the fire prevention materials (thickness 3 mm) of Example 3, Example 4, and Comparative Example 2 was placed between two exterior sheets (manufactured by Toppan Printing Co., Ltd., "GX-PF", thickness 200 μm, water vapor permeability 0.05 g / m 2 The outer periphery was sealed to produce an exterior body. This resulted in a fire prevention material with an exterior body. The fire prevention material with this exterior body was evaluated for fire spread prevention according to the method described in "5-2. Evaluation of fire spread prevention property." The results are shown in Table 3 below.

[0062] [Table 3]

[0063] 6. Simulated Combustion Test FIG. 6 is a schematic diagram showing the configuration of a battery cell assembly for a simulated combustion test. (Test Example 1) First, four battery cells ("laminated type", "capacity approximately 80 Ah") were prepared. The size of each battery cell was 545 mm in total length, 98 mm in width, 9 mm in thickness, and the weight was 1.1 kg. A sheet of the fire spread prevention material (thickness 1 mm) of Example 3 was placed between each pair of adjacent battery cells. In other words, the battery cell spacing was 1 mm. With Bakelite plates placed above and below this laminate, it was fixed in place with a restraining jig. This produced a battery cell assembly. A heater was provided on the lower Bakelite plate so as to come into contact with the first battery cell.

[0064] (Test Example 2) A battery cell assembly was produced in the same manner as in Test Example 1, except for the following changes. One fire prevention material (thickness 1.5 mm) of Example 3 was placed between the first battery cell and the second battery cell, one fire prevention material (thickness 1.5 mm) of Example 3 was placed between the second battery cell and the third battery cell, and one fire prevention material (thickness 2 mm) of Example 3 was placed between the third battery cell and the fourth battery cell. That is, the battery cell intervals from the bottom were 1.5 mm, 1.5 mm, and 2 mm, respectively. (Reference example) A battery cell assembly was prepared in the same manner as in Test Example 1, except that nothing was placed between the first battery cell and the second battery cell, and an alumina fiber substrate having a thickness of 1 mm ("Arsen Paper" manufactured by Denka Company Ltd.) was placed between the second battery cell and the third battery cell, and between the third battery cell and the fourth battery cell.

[0065] A power of 800 W was input to the heater of each battery cell assembly, and the time from when the first battery cell ignited until the second battery cell, the third battery cell, and the fourth battery cell ignited was measured. It took about 12 seconds for the first battery cell to ignite. The results are shown in Table 4 below. [Table 4]

[0066] The same effect as above can be obtained even if silica fiber, alumina fiber or alumina-silica fiber is used instead of the glass fiber. [Explanation of symbols]

[0067] 1: Fire prevention material 2: Inorganic fiber base material 3: layer 5: Exterior body 5a: Sheet material 5b: Sheet material 50: Seal part 51: Base material layer 52: Sealing layer 53 :Protective layer SS: Sodium silicate

Claims

1. A fire-spread prevention material, An inorganic fiber substrate containing inorganic fibers, The inorganic fiber substrate is supported by sodium silicate, The aforementioned sodium silicate is a fire-spreading inhibitor in which the rate of decrease in water content from 30°C to 100°C is 0.75% by mass / °C or less.

2. In the fire-spread prevention material according to claim 1, The constituent material of the inorganic fiber is silica (SiO ２ ) and alumina (Al ２ O ３ A fire-spread prevention material comprising at least one selected from the group consisting of ).

3. In the fire-spread prevention material according to claim 1, The inorganic fiber base material is a wet-formed sheet, which is a fire-spread prevention material.

4. In the fire-spread prevention material according to claim 1, The sodium silicate is a fire-spread prevention material that is unevenly distributed on one side of the inorganic fiber substrate.

5. In the fire-spread prevention material according to claim 1, A fire-spread prevention material in which the total thickness of the inorganic fiber base material and the sodium silicate is 5 mm or less.

6. In the fire-spread prevention material according to claim 1, Furthermore, a fire-spread prevention material comprising an outer casing that houses the inorganic fiber base material and the sodium silicate.

7. In the fire-spread prevention material according to claim 6, The aforementioned outer casing has a water vapor transmission rate of 15 g / m³ at 40°C and 90% RH. ２ A fire-spread prevention material having a density of 250 μm or less and a thickness of 250 μm or less.

8. In the fire-spread prevention material according to claim 1, A fire-preventing material used by being placed between two adjacent battery cells in a battery pack comprising two or more battery cells.

9. It is a battery pack, Two or more battery cells, A battery pack comprising a fire-spread prevention material according to any one of claims 1 to 8, disposed between adjacent battery cells.

10. It is an automobile, The car body and An automobile comprising a battery pack according to claim 9, mounted on the automobile body.

Images