Burn-spread prevention material, battery pack, and automobile

Abstract

The present invention addresses the problem of providing a burn-spread prevention material having excellent burn-spread prevention property and high flexibility, a battery pack using the burn-spread prevention material, and an automobile equipped with the battery pack.　According to one embodiment of the present invention, there is provided a burn-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 has a water content of 30 mass% or more at 30°C.

Description

Fire prevention materials, battery packs and automobiles

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

[0002] With the widespread adoption of electric vehicles, development of automotive battery packs and battery cells for use therein is progressing. Among automotive battery packs, batteries using lithium-ion battery (LiB) cells, which have high energy density, are particularly at risk of abnormalities such as thermal runaway. For this reason, development of technologies to improve the safety of battery cells is progressing. For example, Patent Document 1 proposes a heat-absorbing sheet used to prevent sudden temperature increases and thermal runaway (heat escape) caused by internal short circuits in lithium-ion batteries. However, such heat-absorbing sheets do not necessarily have sufficient fire-spread prevention capabilities.

[0003] Therefore, a predetermined SiO ２ / Na ２ A fire spread prevention material has been proposed that includes a layer containing sodium silicate in a molar ratio of 0 and a layer containing inorganic fibers and having a porous structure (see Patent Document 2). In such a fire spread prevention material, the layer containing sodium silicate may solidify upon drying, resulting in a significant decrease in flexibility. In this case, it becomes difficult to wind the fire spread prevention material into a roll. In other words, the fire spread prevention material cannot be manufactured by roll-to-roll processing, and the productivity of the fire spread prevention material decreases.

[0004] JP 2010-53196 A WO 2022 / 270359

[0005] In view of the above circumstances, the present invention provides a fire prevention material that has excellent fire prevention properties and is highly flexible, a battery pack using this fire prevention material, and a vehicle equipped with this battery pack.

[0006] According to one aspect of the present invention, there is provided a fire spread prevention material comprising an inorganic fiber substrate containing inorganic fibers and sodium silicate supported on the inorganic fiber substrate, wherein the sodium silicate has a moisture content of 30 mass% or more at 30°C.

[0007] According to this embodiment, it is possible to provide a fire prevention material that has excellent fire prevention properties and high flexibility.

[0008] Fig. 1 is a schematic diagram showing the state of water molecules present in sodium silicate. Fig. 2 is a cross-sectional view schematically showing an embodiment of a fire spread prevention material. Fig. 3 is a cross-sectional view schematically showing an embodiment of a fire spread prevention material. Fig. 4(a) is a plan view schematically showing an embodiment of a fire spread prevention material equipped with an exterior body. Fig. 4(b) is a side view and an enlarged view showing a cross-section of an end portion schematically showing an embodiment of a fire spread prevention material equipped with an exterior body. Photographs showing the appearance of the fire spread prevention materials of Samples No. 7 to No. 10 after being placed vertically and standing still.

[0009] Hereinafter, embodiments of the present invention 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 (% by mass) of Y based on the total mass of X, and the water content of sodium silicate means the proportion (% by mass) of water based on the total mass of sodium silicate.

[0010] 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 spread prevention material. The fire spread prevention material of this embodiment is used by being placed between two adjacent battery cells of a battery pack having two or more battery cells. Here, the fire spread prevention material is required to have heat insulating properties (fire spread prevention properties) that suppress heat transfer to adjacent battery cells in the event of an abnormality.

[0011] The fire spread prevention material of this embodiment comprises an inorganic fiber substrate containing inorganic fibers and sodium silicate supported on the inorganic fiber substrate. The sodium silicate has a moisture content of 30% by mass or more at 30°C. That is, the sodium silicate contains an appropriate amount of moisture at room temperature. This allows the fire spread prevention material to maintain high flexibility. As a result, the fire spread prevention material can be wound into a roll, i.e., roll-to-roll production of the fire spread prevention material is possible. These characteristics are suitable for mass production of fire spread prevention materials.

[0012] Furthermore, this fire prevention material retains a sufficient amount of moisture even when heated to temperatures of 100°C or higher. As a result, in an emergency, energy greater than the heat of vaporization of water is required to remove the moisture, and the material exhibits excellent heat insulating properties (heat insulating 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. Note that sodium silicate is Na ２ O.nSiO ２ ・mH ２ O (m is 0 or a positive number).

[0013] The moisture content of sodium silicate at 30°C is preferably about 30% by mass to about 60% by mass, more preferably about 30% by mass to about 55% by mass, even more preferably about 35% by mass to about 50% by mass, and particularly preferably about 35% by mass to about 45% by mass. In this case, since sodium silicate contains a more appropriate amount of moisture, the fire spread prevention material can maintain sufficiently high flexibility. In particular, by having the moisture content of sodium silicate at 30°C be equal to or less than the above upper limit, it is possible to preferably prevent the surface of the fire spread prevention material from becoming sticky and making it difficult to handle. This further improves the productivity of the fire spread prevention material and the battery pack. The moisture content of sodium silicate can be measured (determined) by the method described in the Examples.

[0014] The degree of flexibility of a fire spread prevention material can be measured, for example, by its flexural modulus, maximum flexural strength, maximum flexural strain, etc. The flexural modulus of the fire spread prevention material is preferably about 3000 MPa or less, more preferably about 2500 MPa or less, even more preferably about 2000 MPa or less, and particularly preferably about 1500 MPa or less. A fire spread prevention material having such a flexural modulus can be determined to have sufficiently high flexibility. The lower limit of the flexural modulus of the fire spread prevention material is not particularly limited, but is usually about 500 MPa because handling is unlikely to be impaired. The flexural modulus of the fire spread prevention material may be about 500 MPa or more and 3000 MPa or less. The flexural modulus of the fire spread prevention material is measured for a fire spread prevention material with a thickness of 0.6 mm according to JIS K 7171:2016 (ISO 178:2010).

[0015] The maximum bending strength of the fire spread prevention material is preferably about 20 MPa or less, more preferably about 15 MPa or less, even more preferably about 10 MPa or less, and particularly preferably about 5 MPa or less. A fire spread prevention material having such a maximum bending strength can be determined to have sufficiently high flexibility. The lower limit of the maximum bending strength of the fire spread prevention material is not particularly limited, but is usually about 0.5 MPa because it is less likely to reduce handleability. The maximum bending strength of the fire spread prevention material may be about 0.5 MPa or more and 20 MPa or less. The maximum bending strength of the fire spread prevention material is also measured for a fire spread prevention material with a thickness of 0.6 mm using a method in accordance with JIS K 7171:2016 (ISO 178:2010).

[0016] Furthermore, the maximum bending strain of the fire spread prevention material is preferably about 1% or less, more preferably about 0.75% or less, and even more preferably about 0.5% or less. A fire spread prevention material having such a maximum bending strain can be determined to have sufficiently high flexibility. The lower limit of the maximum bending strain of the fire spread prevention material is not particularly limited, but is usually about 0.1% because it is unlikely to reduce handleability. The maximum bending strain of the fire spread prevention material may be about 0.1% or more and 1% or less. The maximum bending strain of the fire spread prevention material is also measured for a fire spread prevention material with a thickness of 0.6 mm using a method in accordance with JIS K 7171:2016 (ISO 178:2010).

[0017] The moisture content of sodium silicate at 100°C is preferably approximately 15% by mass to 35% by mass, more preferably approximately 18% by mass to 32% by mass, and even more preferably approximately 21% by mass to 29% by mass. In this case, sodium silicate contains sufficient moisture even at 100°C, and becomes porous by foaming when heated to 100°C or higher. As a result, in an emergency, the latent heat of vaporization of moisture and the resulting porosity provide excellent insulating properties (insulating effect). Therefore, even if one battery cell were to catch fire in an emergency, the spread of the fire to adjacent battery cells can be prevented or delayed.

[0018] The sodium silicate preferably exhibits a rate of decrease in moisture content from 30°C to 100°C of 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, and therefore has good flexibility, which contributes to improved productivity of the fire spread prevention material and battery pack, and stable operation of the battery pack. The rate of decrease in moisture content (mass% / °C) can be calculated using the following formula 1. Formula 1: Rate of decrease in moisture content (mass% / °C) = ([moisture content of sodium silicate at 30°C] - [moisture content of sodium silicate at 100°C]) / [moisture content of sodium silicate at 30°C] x 100

[0019] Here, the water molecules present in sodium silicate are classified into I: free water, II: water molecules hydrogen-bonded with OH, III: water molecules adsorbed to Na (constituent element), and IV: water molecules present as OH, as shown in Figure 1. The order of evaporation (desorption) of water molecules is thought to be I → II → III → IV (however, evaporation may occur simultaneously).

[0020] Therefore, in the fire prevention material that becomes porous in the high temperature region, sodium silicate contains the above water molecules, thereby exhibiting high heat insulating properties. Furthermore, from the viewpoint of increasing the moisture content in the low temperature (room temperature) region and the high temperature region, Na contained in sodium silicate ２ Increasing the ratio of O (i.e., SiO ２ / Na ２ It is preferable to lower the SiO molar ratio. ２ / Na ２ The O molar ratio is preferably about 3.3 or less, more preferably about 2.7 or less, even more preferably about 1 to 2.5, and particularly preferably about 1.2 to 2.3.

[0021] The fire spread prevention properties of a fire spread prevention material can be evaluated by heating one side of the fire spread prevention material at 650°C for 30 seconds and measuring the surface temperature of the other side of the fire spread prevention material (surface temperature after 30 seconds). The surface temperature of the other side of the fire spread prevention material after 30 seconds is preferably about 180°C or less, more preferably about 150°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. Such a surface temperature may be about 25°C or more and 180°C or less. A fire spread prevention material that exhibits a surface temperature within the above range can be determined to have excellent fire spread prevention properties. The surface temperature can be measured using the method in the examples.

[0022] Furthermore, because battery cells repeatedly expand and contract during charging and discharging of the battery pack, it is preferable that the fire spread prevention material have flexibility that can follow the expansion and contraction of the battery cells. In this case, by combining an inorganic fiber substrate carrying sodium silicate with, for example, a polyurethane sheet material, the fire spread prevention material can be given good flexibility. 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, thereby enabling the battery pack to repeatedly operate (charge and discharge) stably.

[0023] The proportion of sodium silicate in the total of sodium silicate and 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 easier to impart better fire spread prevention properties to the fire spread prevention material, and it is also possible to reduce the weight of the fire spread prevention material. The proportion of the inorganic fiber substrate in the total of sodium silicate and inorganic fiber substrate is preferably about 1% by mass or more and about 40% by mass or less, more preferably about 1% by mass or more and about 35% by mass or less, even more preferably about 5% by mass or more and about 35% by mass or less, particularly preferably about 8% by mass or more and about 30% by mass or less, and most preferably about 10% by mass or more and about 20% by mass or less. In this case, it is easier to impart better fire spread prevention properties to the fire spread prevention material.

[0024] The inorganic fiber substrate is a substrate (e.g., a sheet) composed primarily of inorganic fibers. Such an inorganic fiber substrate has a plurality of voids (pores) formed between the inorganic fibers. That is, the inorganic fiber substrate has a porous structure. For example, a relatively high-viscosity aqueous solution of sodium silicate is prepared, applied to one side of the inorganic fiber substrate, and then dried, thereby forming a layer containing sodium silicate unevenly distributed on one side of the inorganic fiber substrate. Furthermore, for example, a relatively low-viscosity aqueous solution of sodium silicate is prepared, impregnated into the inorganic fiber substrate, and then dried, thereby filling the voids of the inorganic fiber substrate with sodium silicate.

[0025] 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 or less. Here, the average fiber diameter is a value measured by microscope observation such as a scanning electron microscope (SEM) or an optical microscope.

[0026] The inorganic fiber constituting the inorganic fiber substrate may be of one type or of multiple types. Examples of the constituent material of the inorganic fiber constituting the inorganic fiber substrate include silica (SiO ２ ), alumina (Al ２ O ３ ), carbon, silicon carbide (SiC), etc. Among these, the constituent material of the inorganic fiber is silica (SiO ２ ) and alumina (Al ２ O ３ In this case, the fire spread prevention material can be imparted with higher fire spread prevention properties, and the inorganic fiber substrate tends to have excellent shape processability before drying in the manufacturing process.

[0027] 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.

[0028] The content of inorganic fibers in the inorganic fiber substrate is preferably about 60% by mass to 100% by mass, more preferably about 70% by mass to 98% by mass, even more preferably about 80% by mass to 95% by mass, and particularly preferably about 85% by mass to 93% by mass. In this case, the fire spread prevention material can be imparted with excellent fire spread prevention properties.

[0029] The inorganic fiber substrate may further contain an organic binder. The organic binder is, for example, an organic material that binds inorganic fibers together, and one type 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 of room temperature (e.g., 25°C) or less, a water-soluble resin, etc. may be used. Specific examples of the organic binder include, for example, acrylic resins, polyvinyl alcohol resins (such as vinylon), epoxy resins, cellulose such as cellulose microfibrils, polyvinyl chloride resins, etc.

[0030] 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). Furthermore, the cellulose microfibril refers to microfibrillated cellulose fibers. Among these, the organic binder preferably contains at least one selected from the group consisting of acrylic resins, polyvinyl alcohol resins, and epoxy resins. In this case, a fire-spread prevention material with higher fire-spread prevention properties tends to be obtained.

[0031] 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 with better fire spread prevention properties is more easily obtained.

[0032] The inorganic fiber substrate may further contain inorganic particles. Examples of constituent materials of the inorganic particles include silica, aluminum hydroxide, zinc oxide, magnesium carbonate, and aluminum silicate. Examples of particles containing silica include precipitated silica, fumed silica, and colloidal silica. Precipitated silica is amorphous silica particles obtained by a precipitation method, which is a type of wet method, and has a porous structure.

[0033] The average particle size of the inorganic particles is preferably about 0.01 μm or more and about 100 μm or less, more preferably about 0.1 μm or more and about 80 μm or less, even more preferably about 0.5 μm or more and about 80 μm or less, and particularly preferably about 1 μm or more and about 50 μm or less. Here, the average particle size of the inorganic particles is the volume cumulative particle size D50 value measured by a laser diffraction particle size measuring device. Inorganic particles having such an average particle size are easy to handle and can be more easily distributed uniformly in an inorganic fiber substrate.

[0034] The content of inorganic particles in the inorganic fiber substrate is preferably about 20% by mass or more and about 50% by mass or less, more preferably about 25% by mass or more and about 45% by mass or less, and even more preferably about 30% by mass or more and about 40% by mass or less. By containing inorganic particles at such a content, heat insulation properties are improved and a fire spread prevention material with better fire spread prevention properties is obtained. In addition, an inorganic fiber substrate (and thus a fire spread prevention material) that is lighter and has higher mechanical strength can be obtained. Note that, 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 more preferably does not contain inorganic particles.

[0035] 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 or more and about 5% by mass or less, more preferably about 0.3% by mass or more and about 4% by mass or less, and even more preferably about 0.5% by mass or more and about 3% by mass or less. The inorganic fiber substrate may contain sodium silicate (sodium silicate other than sodium silicate having a moisture content of 30% by mass or more at 30 ° C.), or it 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% by mass or less, more preferably about 5% by mass or less, and even more preferably about 3% by mass or less.

[0036] 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, and more preferably a sheet (wet-formed sheet) formed by a wet papermaking method. The wet-formed sheet is preferred from the viewpoint of being particularly excellent in retention of sodium silicate. In the wet papermaking method, an inorganic fiber substrate (nonwoven fabric) is produced by dispersing materials (inorganic fibers, organic binder, etc.) in water, forming the obtained dispersion on a papermaking screen, and drying it. According to this method, an inorganic fiber substrate (nonwoven fabric) having substantially uniformly dispersed voids can be easily obtained. Therefore, wet-formed sheets tend to have substantially uniformly dispersed voids and have excellent retention of sodium silicate.

[0037] The apparent density of the inorganic fiber substrate is 0.08 g / cm ３ 0.2g / cm or more ３ The weight of the inorganic fiber substrate is preferably about 100 g / m or less. ２ Below 170g / m ２ The thickness of the inorganic fiber substrate is preferably about 0.2 mm or more and 3 mm or less.

[0038] 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 a single-layer structure in which the inorganic fiber substrate 2 is impregnated with sodium silicate SS, as shown in FIG. 3 . The sodium silicate unevenly distributed or impregnated in the inorganic fiber substrate may be in a liquid or gel form, but is preferably in a gel form. Gel-form sodium silicate is easily supported on the inorganic fiber substrate and therefore is less likely to fall off from the inorganic fiber substrate during production of the fire spread prevention material 1. The two-layer 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, thereby unevenly distributing the layer 3 containing sodium silicate SS on one side of the inorganic fiber substrate 2. For this coating, gravure coating, slot die coating, knife coating, blade coating, comma coating, reverse roll coating, ink jet coating, etc. are suitably used.

[0039] On the other hand, a single-layer fire prevention material 1 can be produced, for example, by preparing a relatively low-viscosity aqueous solution of sodium silicate SS, impregnating the inorganic fiber substrate 2, and optionally pressurizing and drying the solution to fill the voids in the inorganic fiber substrate 2 with sodium silicate SS. Both of the above fire prevention materials 1 are preferably produced by a roll-to-roll process, in which a long inorganic fiber substrate 2 wound into a roll is fed, an aqueous solution of sodium silicate SS (gel-like sodium silicate SS) is supplied, dried, and then wound into a roll. As described above, the fire prevention material 1 can maintain high flexibility even during its manufacture. This allows for smooth winding of the fire prevention material 1, and cracks and other defects are unlikely to occur in the fire prevention material 1 even after winding into a roll. The resulting long fire prevention material 1 is then cut to a predetermined length for use.

[0040] The drying temperature is not particularly limited, but is preferably about 80°C to 130°C, more preferably about 90°C to 120°C, and even more preferably about 100°C to 115°C. Drying within this temperature range makes it possible to adjust the water content of sodium silicate to the desired range in a relatively short time. The drying time is appropriately set depending on the drying temperature, and is preferably about 0.1 to 15 minutes, more preferably about 0.5 to 12.5 minutes, even more preferably about 1 to 10 minutes, particularly preferably about 1.5 to 10 minutes, and most preferably about 2 to 7.5 minutes.

[0041] In the configuration example of Figure 2, layer 3, and in the configuration example of Figure 3, fire spread prevention material 1 (hereinafter referred to as "sodium silicate-containing portion") preferably absorb heat in the temperature range of 100°C or higher and 300°C or lower. Furthermore, when the sodium silicate-containing portion is heated from 100°C to 300°C at 10°C / min, the mass loss rate is preferably 15% by mass or higher. The heat absorption of the sodium silicate-containing portion is thought to occur when moisture in the sodium silicate-containing portion (for example, water molecules in sodium silicate SS) undergoes an endothermic reaction in the temperature range of 100°C or higher and 300°C or lower. On the other hand, the mass loss of the sodium silicate-containing portion is thought to occur due to this endothermic reaction.

[0042] Therefore, the mass loss rate when the sodium silicate-containing portion is heated from 100°C to 300°C at 10°C / min correlates with the amount of water contained in the sodium silicate-containing portion and the amount of heat absorbed. Therefore, it is presumed that a mass loss rate of the sodium silicate-containing portion of 15% by mass or more increases the amount of heat absorbed in the above temperature range, thereby providing sufficient fire spread prevention properties for the fire prevention material. The heat absorption of the sodium silicate-containing portion can be confirmed, for example, by thermogravimetry-differential thermal analysis (TG-DTA) measurement, based on the presence or absence of an endothermic peak in the temperature range of 100°C to 300°C.

[0043] The mass loss rate when the sodium silicate-containing portion is heated from 100°C to 300°C at 10°C / min is preferably about 15% by mass to 30% by mass, more preferably about 17% by mass to 28% by mass, even more preferably about 20% by mass to 25% by mass, particularly preferably about 23% by mass to 25% by mass, and most preferably about 23.5% by mass to 25% by mass. In this case, a fire spread prevention material with better fire spread prevention properties is easily obtained. The mass loss rate can be calculated using the following formula 2. Formula 2: Mass loss rate (mass%) = [mass loss of sodium silicate-containing portion] / [mass of sodium silicate-containing portion at 100°C] x 100

[0044] 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 a plurality of sodium silicate-containing portions are present, the mass loss rate of each sodium silicate-containing portion may be within the above range, or the total mass loss rate of all the sodium silicate-containing portions may be within the above range.

[0045] The fire spread prevention material preferably has insulating properties. In this case, for example, by protecting both sides of the inorganic fiber substrate carrying sodium silicate with a resin sheet material or by housing the inorganic fiber substrate carrying sodium silicate in an exterior body 5 described below, 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 1×10 or more. 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.

[0046] 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 placed opposite the fire spread prevention material). Specific examples of shapes include a sheet shape with unevenness on the surface, a sheet shape with curved portions 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. A fire spread prevention material processed into a predetermined shape can be manufactured by the manufacturing method described below, thereby preventing separation and breakage between the inorganic fiber substrate 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).

[0047] The total thickness of the inorganic fiber substrate and sodium silicate (the thickness of one sheet of fire 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 prevention material with higher fire prevention properties can be obtained, and the installation space for the fire prevention material within the battery pack can be prevented from becoming too large. Note that multiple sheets of the fire prevention material 1 may be stacked.

[0048] As shown in Fig. 4, the fire spread prevention material 1 may further include an exterior body 5 that houses the inorganic fiber substrate 2 and sodium silicate SS. In other words, the fire spread prevention material 1 can also be said to include a fire spread prevention material main body, which is the inorganic fiber substrate 2 carrying sodium silicate SS, and an exterior body 5 that houses this fire spread prevention material main body. By housing sodium silicate SS within 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 schematically showing an embodiment of a fire spread prevention material that includes an exterior body. Fig. 4(b) is an enlarged view showing a side view and a cross section of an end portion that schematically show an embodiment of a fire spread prevention material that includes an exterior body.

[0049] The water vapor transmission rate of the exterior body 5 at 40°C and 90% RH is 15 g / m ２ / day or less, and ２ / day or less is more preferable, and ２ / day or less, and ２ It is particularly preferable that the lower limit of the water vapor transmission rate of the exterior body 5 at 40°C and 90% RH is 0.01 g / m ２ The water vapor transmission rate of the exterior body 5 at 40°C and 90% RH is about 0.01 g / m ２ / day or more 15g / m ２ / day or less. 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 fire spread prevention. The water vapor transmission rate (water vapor permeability) is measured by a method in accordance with JIS K 7129-2:2019.

[0050] The outer peripheries of two sheet materials 5a, 5b are sealed with a seal portion 50, and the composite of the inorganic fiber substrate 2 and sodium silicate SS is contained inside the outer peripheries of the two sheet materials 5a, 5b. 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, or heat fusion). Alternatively, one sheet material may be folded in half and its periphery sealed with a seal portion to contain the composite of the inorganic fiber substrate 2 and sodium silicate SS inside. In this embodiment, each sheet material 5a, 5b is a laminate including a base layer 51, a seal layer 52 provided on the inner side of the base layer 51, and a protective layer 53 provided on the outer side of the base layer 51.

[0051] The substrate layer 51 has functions such as imparting mechanical strength to the sheet materials 5a and 5b and regulating (blocking) moisture (water vapor) permeation. The substrate layer 51 may be made of a metal foil. Examples of materials for this metal foil include aluminum or an aluminum alloy, nickel or a nickel alloy, and stainless steel. The thickness of the substrate layer 51 is not particularly limited, but is preferably approximately 5 μm to 100 μm, more preferably approximately 8 μm to 80 μm, and even more preferably approximately 12 μm to 60 μm. In this case, the sheet materials 5a and 5b can have adequate water vapor permeability and sufficient flexibility.

[0052] The sealing layer 52 functions to seal the exterior body 5 by being fused. Examples of materials (fusible materials) that can be used for 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, and polymethylpentene. Polypropylene is a more preferred material for the sealing layer 52, and unstretched polypropylene is even more preferred. The thickness of the sealing layer 52 is not particularly limited, but is preferably approximately 5 μm to 200 μm, more preferably approximately 10 μm to 100 μm, even more preferably approximately 20 μm to 120 μm, and particularly preferably approximately 30 μm to 80 μm. This allows for improved sealing while maintaining the flexibility of the sheet materials 5a and 5b.

[0053] The protective layer 53 has a function of protecting the base layer 51 (preventing corrosion of the base 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-containing resins, and polyester resins. The thickness of the protective layer 53 is not particularly limited, but is preferably about 5 μm to 100 μm, more preferably about 10 μm to 50 μm, and even more preferably about 15 μm to 30 μm.

[0054] The thickness of the exterior body 5 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 permeability 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), thereby further improving fire spread prevention. Note that 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.

[0055] The above describes a fire spread prevention material according to one embodiment, but the fire spread prevention material of the present invention is not limited to the above embodiment. Another embodiment of the present invention provides a battery pack including two or more battery cells and the fire spread prevention material arranged between adjacent battery cells. This battery pack is, for example, a lithium ion battery. Another embodiment of the present invention provides a vehicle including a vehicle body and the battery pack installed in the vehicle body. Furthermore, the fire spread prevention material may be provided in each of the following aspects.

[0056] (1) A fire spread prevention material comprising an inorganic fiber substrate containing inorganic fibers and sodium silicate supported on the inorganic fiber substrate, wherein the sodium silicate has a moisture content of 30% by mass or more at 30°C.

[0057] (2) The fire prevention material according to (1) above, wherein the sodium silicate has a moisture content of 60% by mass or less at 30°C.

[0058] (3) The fire spread prevention material according to (1) or (2) above, wherein the fire spread prevention material has a flexural modulus of elasticity of 3000 MPa or less.

[0059] (4) A fire prevention material according to any one of (1) to (3) above, wherein the fire prevention material has a maximum bending strength of 20 MPa or less.

[0060] (5) A fire prevention material according to any one of (1) to (4) above, wherein the fire prevention material has a maximum bending strain of 1% or less.

[0061] (6) In the fire prevention material according to any one of (1) to (5) above, the sodium silicate is a SiO ２ / Na ２ A fire prevention material having an O molar ratio of 3.3 or less.

[0062] (7) In the fire prevention material described in any one of (1) to (6) above, the sodium silicate is unevenly distributed on one side of the inorganic fiber substrate or is impregnated into the inorganic fiber substrate.

[0063] (8) The fire prevention material according to any one of (1) to (7) above, wherein the total thickness of the inorganic fiber substrate and the sodium silicate is 5 mm or less.

[0064] (9) The fire prevention material according to any one of (1) to (8) above, further comprising an exterior body that accommodates the inorganic fiber base material and the sodium silicate.

[0065] (10) In the fire prevention material described in (9) above, the exterior body has a water vapor permeability of 15 g / m at 40°C and 90% RH. ２ / day or less and a thickness of 250 μm or less.

[0066] (11) A battery pack comprising two or more battery cells and a fire prevention material according to any one of (1) to (10) above, disposed between adjacent battery cells.

[0067] (12) An automobile comprising: an automobile body; and the battery pack according to (11) above, mounted in the automobile body. Of course, this is not a limitation.

[0068] Finally, while various embodiments of the present disclosure have been described, they are presented as examples and are not intended to limit the scope of the invention. The novel embodiments may be embodied in various other forms, and various omissions, substitutions, and modifications may be made without departing from the spirit of the invention. Such embodiments and modifications are intended to be included within the scope and spirit of the invention, as well as within the scope of the inventions and their equivalents as defined in the claims.

[0069] 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.

[0070] 1. Preparation of materials <Sodium silicate> SS: SiO ２ / Na ２ O mole ratio = 2.0 to 2.3, gel state <Inorganic fiber> F1: Glass fiber (average fiber diameter 10 μm) <Organic binder> B1: Vinylon fiber (average fiber diameter 5 μm)

[0071] 2. Preparation of inorganic fiber substrate (wet-formed 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. This dispersion was formed into a papermaking screen and dried using a Yankee dryer to produce a wet-formed sheet (nonwoven fabric). The size of the wet-formed sheet was 100 mm long x 100 mm wide x 0.6 mm thick, and the basis weight was 120 g / m ２ It was.

[0072] 3A. Preparation of fire prevention material (Sample No. 1: Example) Sodium silicate was added at 900 g / m ２The solution was impregnated into a wet-laid sheet (inorganic fiber substrate) so that the sodium silicate content was 0.6 mm, compressed with a roller, and then dried at 115°C for 3 minutes. Five single-layer fire prevention materials were thus produced, in which the voids in the wet-laid sheet were filled with sodium silicate. The thickness of the resulting fire prevention materials was 0.6 mm. (Sample No. 2: Example) Five single-layer fire prevention materials were produced in the same manner as Sample No. 1, except that the drying time was changed to 5 minutes. The thickness of the resulting fire prevention materials was 0.6 mm.

[0073] (Sample No. 3: Example) Five single-layer fire prevention materials were produced in the same manner as Sample No. 1, except that the drying time was changed to 7 minutes. The thickness of the resulting fire prevention materials was 0.6 mm. (Sample No. 4: Comparative Example) Five single-layer fire prevention materials were produced in the same manner as Sample No. 1, except that the drying time was changed to 9 minutes. The thickness of the resulting fire prevention materials was 0.6 mm.

[0074] (Sample No. 5: Comparative Example) Five single-layer fire prevention materials were produced in the same manner as Sample No. 1, except that the drying time was changed to 11 minutes. The thickness of the resulting fire prevention materials was 0.6 mm. (Sample No. 6: Comparative Example) Five single-layer fire prevention materials were produced in the same manner as Sample No. 1, except that the drying time was changed to 13 minutes. The thickness of the resulting fire prevention materials was 0.6 mm.

[0075] 4A. Measurement and Evaluation 4A-1. Measurement of Moisture Content For each of the fire spread prevention materials, Samples 1 to 6, the mass change up to 1000°C was measured using a thermogravimetric analyzer (NETZSCH Japan, "High Sensitivity Differential Thermobalance STA 2500 Regulus"). The measured value at 1000°C was defined as the "solid content contained in each of the fire spread prevention materials, Samples 1 to 6," and the moisture content at 30°C of each of the fire spread prevention materials (≒ sodium silicate) for Samples 1 to 6 was calculated from this solid content value and the measured value from the thermogravimetric analysis.

[0076] 4A-2. Measurement of the amount of sodium silicate supported The difference between the mass of the fire prevention material and the mass of the wet-processed sheet for each of Samples No. 1 to No. 6 was calculated, and divided by the planar area of ​​the fire prevention material to determine the amount of sodium silicate supported (g / m ２ )

[0077] 4A-2. Elastic modulus of fire retardant material The flexural modulus of the fire retardant material was measured according to the method in accordance with JIS K 7171:2016. 4A-3. Maximum bending strength of fire retardant material The maximum bending strength of the fire retardant material was measured according to the method in accordance with JIS K 7171:2016. 4A-4. Maximum bending strain of fire retardant material The maximum bending strain of the fire retardant material was measured according to the method in accordance with JIS K 7171:2016.

[0078] The results are shown in Table 1. The flexural modulus, maximum flexural strength and maximum flexural strain in Table 1 are each the average values ​​measured for five samples.

[0079] 4A-5. Cylinder wrapping test Three pieces of each fire prevention material from Samples No. 1 to No. 6 were wrapped around four types of cylinders with different diameters, and evaluated according to the following criteria: A: No cracks occurred. B: Cracks occurred. C: Fracture occurred.

[0080] The results are shown in Table 2 below.

[0081] 4A-6. Evaluation of Fire Spread Prevention One fire spread prevention material, one aluminum thin plate (thickness: 0.5 mm), a K thermocouple, two glass fiber sheets (thickness per sheet: 0.6 mm), and an aluminum block (500 g) were stacked in this order on a hot plate ("PA8015" manufactured by MSA Factory) heated to 650°C. The back surface temperature of the fire spread prevention material (the surface temperature on the side opposite the hot plate) was measured after 30 seconds.

[0082] The results are shown in Table 3 below. The fire spread prevention materials of Samples No. 1 to No. 6 all had a back surface temperature of 180°C or less, and exhibited excellent fire spread prevention properties.

[0083] 3B. Preparation of fire prevention material (Sample No. 7: Example) Sodium silicate was added at 900 g / m ２ The solution was impregnated into a wet-formed sheet (inorganic fiber substrate) and compressed with a roller so that the thickness was 0.6 mm. This resulted in four fire prevention materials with a single layer structure, in which sodium silicate was filled into the voids of the wet-formed sheet. The resulting fire prevention materials had a thickness of 0.6 mm. (Sample No. 8: Example) Four fire prevention materials with a single layer structure were produced in the same manner as Sample No. 7, except that the drying time was changed to 1 minute. The resulting fire prevention materials had a thickness of 0.6 mm.

[0084] (Sample No. 9: Example) Four single-layer fire prevention materials were produced in the same manner as Sample No. 7, except that the drying time was changed to 2 minutes. The thickness of the resulting fire prevention materials was 0.6 mm. (Sample No. 10: Example) Four single-layer fire prevention materials were produced in the same manner as Sample No. 7, except that the drying time was changed to 3 minutes. The thickness of the resulting fire prevention materials was 0.6 mm.

[0085] (Sample No. 11: Example) Four single-layer fire prevention materials were produced in the same manner as Sample No. 7, except that the drying time was changed to 4 minutes. The thickness of the resulting fire prevention materials was 0.6 mm. (Sample No. 12: Example) Four single-layer fire prevention materials were produced in the same manner as Sample No. 7, except that the drying time was changed to 5 minutes. The thickness of the resulting fire prevention materials was 0.6 mm.

[0086] 4B. Measurement and Evaluation 4B-1. Measurement of Moisture Content For each of the fire prevention materials of Samples No. 7 to No. 12, the moisture content of the fire prevention material (≒ sodium silicate) at 30°C was determined in the same manner as in "4A-1. Measurement of Moisture Content" above.

[0087] 4B-2. Evaluation of surface peelability Two pieces of each of the fire spread prevention materials from Samples No. 7 to No. 12 were sandwiched between PET films, and an aluminum block (500 g) was placed on top of them. After 10 seconds, the peelability between the fire spread prevention materials was checked. Evaluation was then made according to the following criteria: A: The two fire spread prevention materials could be easily peeled off. B: The two fire spread prevention materials were difficult to peel off.

[0088] The results are shown in Table 4 below.

[0089] As shown in Table 4, fire prevention materials that have a low moisture content and are in a dried, gel-like state (a state in which fluidity is sufficiently low or non-existent) have low surface tackiness and are easy to handle regardless of the environmental atmosphere of the manufacturing process. Therefore, it is clear that sodium silicate in a gel-like state is preferable in the manufacture of fire prevention materials.

[0090] 4B-2. Evaluation of fluidity Each of the fire prevention materials of Samples No. 7 to No. 12 was sealed with a barrier film. This sealed material was then left standing for three days, either vertically (vertically) or horizontally (flat) on the ground. Each of Samples No. 7 to No. 12 was then divided in half, and the mass of each half (the upper and lower half when placed vertically, or the left and right half when placed flat) was measured.

[0091] The results are shown in Tables 5 and 6 below.

[0092]

[0093] For fire prevention materials with low moisture content at 30°C, almost no difference in mass was observed between the top and bottom of each sample, even when placed upright. This is the result of preventing or suppressing the flow of sodium silicate due to gravity. Therefore, in order to maintain homogeneity in the product, it is preferable that the sodium silicate be in a highly dried gel state (a state with sufficiently low or no fluidity).

[0094] The appearance of the fire spread prevention materials of Samples No. 7 to No. 10 after being left standing vertically is shown in Figure 5. Figure 5 is a photograph showing the appearance of the fire spread prevention materials of Samples No. 7 to No. 10 after being left standing vertically. As shown in Figure 5, in the fire spread prevention material of Sample No. 10, which has a low moisture content, the sodium silicate does not easily flow downward due to gravity during standing, and the amount of sodium silicate in the upper portion is sufficiently maintained, confirming that this upper portion does not become extremely dry.

[0095] From the above, it can be seen that by adjusting the moisture content of sodium silicate at 30°C within a predetermined range, a long fire spread prevention material body (fire spread prevention material) containing such sodium silicate can be easily wound into a roll during production, and cracks, etc. are unlikely to occur even after being wound into a roll. It can also be seen that the fire spread prevention material body (fire spread prevention material) has excellent peelability and is unlikely to stick even after being wound into a roll.

[0096] 1: Fire prevention material, 2: Inorganic fiber substrate, 3: Layer, 5: Exterior body, 5a: Sheet material, 5b: Sheet material, 50: Sealing portion, 51: Base material layer, 52: Sealing layer, 53: Protective layer, SS: Sodium silicate

Claims

1. A fire prevention material comprising: an inorganic fiber substrate containing inorganic fibers; and sodium silicate supported on the inorganic fiber substrate, wherein the sodium silicate has a moisture content of 30% by mass or more at 30°C.

2. A fire prevention material according to claim 1, wherein the sodium silicate has a moisture content of 60% by mass or less at 30°C.

3. A fire prevention material according to claim 1, wherein the fire prevention material has a flexural modulus of elasticity of 3000 MPa or less.

4. A fire prevention material according to claim 1, wherein the fire prevention material has a maximum bending strength of 20 MPa or less.

5. A fire prevention material according to claim 1, wherein the maximum bending strain of the fire prevention material is 1% or less.

6. In the fire prevention material according to claim 1, the sodium silicate has a SiO ２ / Na ２ A fire prevention material having an O molar ratio of 3.3 or less.

7. A fire prevention material according to claim 1, wherein the sodium silicate is unevenly distributed on one side of the inorganic fiber substrate or is impregnated into the inorganic fiber substrate.

8. A fire prevention material according to claim 1, wherein the total thickness of the inorganic fiber base material and the sodium silicate is 5 mm or less.

9. A fire prevention material according to claim 1, further comprising an exterior body that houses the inorganic fiber base material and the sodium silicate.

10. The fire prevention material according to claim 9, wherein the exterior body has a water vapor permeability of 15 g / m at 40°C and 90% RH. ２ / day or less and a thickness of 250 μm or less.

11. An assembled battery comprising: two or more battery cells; and a fire prevention material according to any one of claims 1 to 10, disposed between adjacent battery cells.

12. A vehicle comprising: a vehicle body; and the battery pack according to claim 11 mounted in the vehicle body.

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