Fire spread prevention material, battery pack, and automobile

Abstract

[Problem] To provide a fire spread prevention material capable of sufficient fire spread prevention, a battery pack utilizing said fire spread prevention material, and an automobile comprising said battery pack. [Solution] One aspect of the present invention provides such a fire spread prevention material. The fire spread prevention material comprises an inorganic-fiber base material which includes inorganic fibers, and sodium silicate which is held on the inorganic-fiber base material. Provided that the average temperature rise rate from 100°C to 200°C when the fire spread prevention material is heated is V [°C / sec], and the thickness of the fire spread prevention material after exceeding 200°C is Da [mm], V × Da is 20 or less.

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 runaway) caused by internal short circuits in lithium-ion batteries. However, such heat-absorbing sheets do not necessarily have sufficient fire-spread prevention capabilities.

[0003] JP 2010-53196 A

[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.

[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. When the fire spread prevention material is heated, the average temperature rise rate from 100°C to 200°C is V [°C / sec], and the thickness of the fire spread prevention material after 200°C is Da [mm], V × Da is 20 or less.

[0006] According to this aspect, sufficient fire spread prevention properties can be exhibited.

[0007] 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 including an exterior body. Fig. 4(b) is an enlarged view showing a side view and a cross-section of an end portion schematically showing an embodiment of a fire spread prevention material including an exterior body.

[0008] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. Various features described in the following embodiments can be combined with each other. In this specification, the content of Y in X refers to the proportion (mass%) of Y based on the total mass of X, and the water content of sodium silicate refers to 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. FIGS. 2 and 3 are cross-sectional views each showing a schematic embodiment of a fire spread 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 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.

[0009] The fire spread prevention material of the present invention comprises an inorganic fiber substrate containing inorganic fibers and sodium silicate supported on the inorganic fiber substrate. ２ O.nSiO ２ ・mH ２ 0 (m is 0 or a positive number). When the average temperature rise rate from 100°C to 200°C when the fire spread prevention material is heated is V [°C / sec], and the thickness of the fire spread prevention material after 200°C (after evaluation of fire spread prevention described in the examples) is Da [mm], V x Da is about 20 or less, preferably about 17 or less, more preferably about 14 or less, and even more preferably about 11 or less. When multiple fire spread prevention materials are used in a stacked configuration, Da means the total thickness.

[0010] The fire spread prevention material foams upon heating, improving its thermal insulation properties. When the temperature rise rate from 100°C to 200°C of this foamed fire spread prevention material (foam) with a thickness Da of 6.7 mm was measured using the method described in the Examples, the average temperature rise rate V was 3.3°C / sec. Because the average temperature rise rate is inversely proportional to the thickness, the value of average temperature rise rate x thickness (V x Da) was found to adequately reflect the fire spread prevention or delay effect required of the fire spread prevention material, leading to the completion of the present invention. The V x Da value of the foam is calculated to be 22.1. Therefore, it is important to design the V x Da value to be below this value (20 or less). A fire spread prevention material designed in this way can maintain a relatively gradual temperature rise even after exceeding 100°C upon heating. Therefore, even if one battery cell ignites during an abnormal event, the spread of fire to adjacent battery cells can be prevented or delayed. The lower limit of V×Da is not particularly limited, but is about 5, for example.

[0011] 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 120 seconds and measuring the surface temperature of the other side of the fire spread prevention material (surface temperature after 120 seconds). 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. 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.

[0012] 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.

[0013] Furthermore, the moisture content of sodium silicate at 30°C is preferably about 60% by mass or less, more preferably about 40% by mass to 60% by mass, and even more preferably about 45% by mass to 55% by mass. Because such sodium silicate contains an appropriate amount of moisture, the temperature rise of the fire prevention material after it exceeds 100°C can be sufficiently gradual. Furthermore, the fire prevention material can maintain high flexibility during production of the fire prevention material, storage of the fire prevention material, production of the battery pack, and the like. As a result, the productivity of the fire prevention material and the battery pack can also be improved.

[0014] 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 insulation (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. The moisture content of sodium silicate can be measured (determined) using the method described in the Examples.

[0015] The sodium silicate preferably exhibits a moisture content decrease rate of about 0.75% by mass / °C or less from 30°C to 100°C, 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 moisture content decrease rate (mass% / °C) can be calculated using the following formula 1. Formula 1: Moisture content decrease rate (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

[0016] Here, the state of water molecules present in sodium silicate is classified as I: free water, II: water molecules hydrogen-bonded with OH, III: water molecules adsorbed to Na, and IV: water molecules present as OH, as shown in Figure 1. The order of evaporation as water molecules is thought to be I → II → III → IV (however, they may occur simultaneously). For this reason, sodium silicate exhibits high heat insulating properties in a fire prevention material that becomes porous in a high-temperature region by containing the above water molecules. Furthermore, from the viewpoint of increasing the moisture content in a high-temperature region, the 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.

[0017] In addition, the water molecules adsorbed on Na have a strong bond and are thought to be difficult to separate even at relatively high temperatures. ２ Increasing the proportion of O makes it easier to prevent a sudden temperature rise after the temperature of the fire prevention material exceeds 100°C. Therefore, even if one battery cell were to catch fire in an emergency, the spread of the fire to adjacent battery cells can be more reliably prevented or delayed. In addition, the use of such sodium silicate can further increase the productivity of the fire prevention material and battery packs.

[0018] 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.

[0019] 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 layer containing sodium silicate can be unevenly distributed on one surface of the inorganic fiber substrate by applying a relatively high-viscosity sodium silicate to one surface of the inorganic fiber substrate and then drying it. Furthermore, for example, an aqueous solution of sodium silicate with a relatively low viscosity can be prepared, impregnated into the inorganic fiber substrate, and then dried, thereby filling the voids of the inorganic fiber substrate with sodium silicate.

[0020] 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.

[0021] 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 ) It is preferable that the inorganic fiber substrate contains at least one selected from the group consisting of. In this case, higher fire spread prevention properties can be imparted to the fire spread prevention material, and in the manufacturing process of the inorganic fiber substrate, it tends to have excellent shape processability before drying. Examples of such inorganic fibers include glass fiber, silica fiber, alumina-silica fiber, alumina fiber, basalt fiber, rock wool, etc. Among these, it is preferable that the inorganic fiber substrate contains at least one of glass fiber, silica fiber, and alumina-silica fiber. In this case, the above-mentioned effects can be further improved.

[0022] The content of inorganic fibers in the inorganic fiber substrate is preferably approximately 60% by mass or more and 100% by mass or less, more preferably approximately 70% by mass or more and 98% by mass or less, even more preferably approximately 80% by mass or more and 95% by mass or less, and particularly preferably approximately 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 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 (e.g., 25°C) or a water-soluble resin may be used. Specific examples of organic binders include, for example, acrylic resins, polyvinyl alcohol resins (such as vinylon), epoxy resins, cellulose such as cellulose microfibrils, polyvinyl chloride resins, etc.

[0023] 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, cellulose microfibrils refer to microfibrillated cellulose fibers. In particular, 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. 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-spread prevention material with better fire-spread prevention properties is more easily obtained.

[0024] 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 silica-containing particles include precipitated silica, fumed silica, and colloidal silica. Precipitated silica is an amorphous silica particle 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 0.01 μm to about 100 μm, more preferably about 0.1 μm to about 80 μm, even more preferably about 0.5 μm to about 80 μm, and particularly preferably about 1 μm to about 50 μm. Here, the average particle size of the inorganic particles is the volume cumulative particle size D50 value measured using a laser diffraction particle size analyzer. Inorganic particles having such an average particle size are easy to handle and can be more uniformly distributed in the inorganic fiber substrate.

[0025] 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.

[0026] 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 to 35% by mass), 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% by mass or less, more preferably about 5% by mass or less, and even more preferably about 3% by mass or less.

[0027] As the inorganic fiber substrate, for example, a substrate excellent in 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, a wet-formed sheet is likely to have substantially uniformly dispersed voids and tends to have excellent retention of sodium silicate. The apparent density of the inorganic fiber substrate is 0.08 g / cm ３ 0.2g / cm or more ３ The weight per unit area of ​​the inorganic fiber substrate is preferably about 100 g / m when the thickness is 1 mm. ２ 170g / m or less ２ The thickness of the inorganic fiber substrate is preferably 0.2 mm or more and 3 mm or less.

[0028] 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 Figure 2, or a single-layer structure in which the inorganic fiber substrate 2 is impregnated with sodium silicate SS, as shown in Figure 3. The two-layer fire spread prevention material 1 can be formed, for example, by applying relatively high-viscosity sodium silicate SS 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 application, gravure coating, slot die coating, knife coating, blade coating, comma coating, reverse roll coating, inkjet coating, or the like is preferably used.

[0029] On the other hand, a single-layer fire prevention material 1 can be produced, for example, by impregnating an inorganic fiber substrate 2 with sodium silicate SS having a relatively low viscosity, pressurizing it as necessary, and then drying it to fill the voids in the inorganic fiber substrate 2 with sodium silicate SS. Here, the viscosity of the sodium silicate SS at 20°C is preferably about 100 mPa·s or more, more preferably about 500 mPa·s to 10,000 mPa·s, even more preferably about 1,000 mPa·s to 8,000 mPa·s, and particularly preferably about 1,500 mPa·s to 5,000 mPa·s. Using sodium silicate SS with such a viscosity prevents the sodium silicate SS from dripping from the inorganic fiber substrate 2, making it easier to support the sodium silicate SS on the inorganic fiber substrate 2. The water content and viscosity of the sodium silicate SS may be adjusted by adding water.

[0030] The fire spread prevention material 1, whether having a one-layer structure or a two-layer structure, is suitably produced by a roll-to-roll process in which a rolled-up inorganic fiber substrate 2 is fed, sodium silicate SS is supplied, the substrate is dried, and the substrate is then wound into a roll. As described above, the fire spread prevention material 1 can maintain high flexibility even during the production of the fire spread prevention material 1. This allows the fire spread prevention material 1 to be smoothly wound into a roll, and cracks and the like are less likely to occur in the fire spread prevention material 1 even after it has been wound into a roll.

[0031] 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 (e.g., water molecules in sodium silicate) 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.

[0032] 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.

[0033] When the sodium silicate-containing portion is heated from 100°C to 300°C at a rate of 10°C / min, the mass loss rate 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] × 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 there are multiple sodium silicate-containing portions, the mass loss rate of each sodium silicate-containing portion may be in the above range, or the total mass loss rate of all the sodium silicate-containing portions may be in the above range.

[0034] 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 later, 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 ８This means that the resistance is Ω·cm or more. The fire spread prevention material may be in the form of a sheet (e.g., a flat plate) 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 follows 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 an uneven 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, 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).

[0035] Once processed into a predetermined shape, the fire spread prevention material can maintain that shape. The ability of the fire spread prevention material to maintain its predetermined shape can be quantified by its three-point bending strength. Specifically, the three-point bending strength of the fire spread prevention material measured according to JIS K 7171 is preferably approximately 0.5 MPa to 5 MPa, more preferably approximately 0.8 MPa to 4 MPa, and even more preferably approximately 1 MPa to 3 MPa. A fire spread prevention material with such three-point bending strength can be said to have sufficient strength to maintain its predetermined shape. The total thickness of the inorganic fiber substrate and sodium silicate (the thickness of one sheet of fire spread prevention material 1 in the configuration examples of Figures 2 and 3) is preferably approximately 5 mm or less, preferably approximately 0.5 mm to 5 mm, more preferably approximately 1 mm to 4 mm, and even more preferably approximately 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 installation space for the fire spread prevention material within the battery pack can be prevented from becoming too large.

[0036] 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 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 that schematically show an embodiment of a fire spread prevention material that includes an exterior body. 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 at 40°C is 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 fire spread prevention. The water vapor transmission rate (water vapor permeability) is measured by a method in accordance with JIS K 7129-2:2019.

[0037] 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.

[0038] 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.

[0039] 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.

[0040] 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.

[0041] The thickness of the exterior body is not particularly limited, but is preferably approximately 250 μm or less, more preferably approximately 200 μm or less, and even more preferably approximately 100 μm or less. In this case, it is 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 have a single layer (one layer) structure, a two-layer structure, or a four-layer or more structure depending on the required characteristics. While 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 fire spread prevention material disposed between adjacent battery cells. The battery pack is, for example, a lithium-ion battery. As another embodiment of the present invention, there is provided a vehicle including a vehicle body and the battery pack installed in the vehicle body. Furthermore, the present invention may be provided in the following aspects.

[0042] (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, wherein when the average temperature rise rate from 100°C to 200°C when the fire spread prevention material is heated is V [°C / sec] and the thickness of the fire spread prevention material after 200°C is Da [mm], V x Da is 20 or less.

[0043] (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.

[0044] (3) In the fire prevention material described in (1) or (2) above, the sodium silicate is ２ / Na ２ A fire prevention material having an O molar ratio of 3.3 or less.

[0045] (4) A fire prevention material according to any one of (1) to (3) above, wherein the viscosity of the sodium silicate at 20°C is 100 mPa·s or more.

[0046] (5) In the fire prevention material according to any one of (1) to (4) above, the constituent material of the inorganic fiber is silica (SiO ２ ) and alumina (Al ２ O ３ ) A fire prevention material comprising at least one selected from the group consisting of:

[0047] (6) The fire prevention material according to any one of (1) to (5) above, wherein the inorganic fiber substrate is a wet-formed sheet.

[0048] (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.

[0049] (8) In the fire prevention material according to any one of (1) to (7) above, the total thickness of the inorganic fiber substrate and the sodium silicate is 5 mm or less.

[0050] (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.

[0051] (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.

[0052] (11) The fire spread prevention material according to any one of (1) to (10) above, wherein the fire spread prevention material is disposed between two adjacent battery cells of a battery pack having two or more battery cells.

[0053] (12) A battery pack comprising two or more battery cells and a fire prevention material according to any one of (1) to (11) above, disposed between adjacent battery cells.

[0054] (13) An automobile comprising: an automobile body; and the battery pack according to (12) above, mounted in the automobile body. Of course, this is not a limitation.

[0055] 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 invention and its equivalents as defined in the claims.

[0056] 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.

[0057] 1. Preparation of materials <Sodium silicate> SS1: SiO ２ / Na ２ O molar ratio = 2.1 (water content at 30°C: 53.9 mass%, viscosity at 20°C: 1130 mPa s) SS2: SiO ２ / Na ２O molar ratio = 2.1 (water content at 30°C: 50.8 mass%, viscosity at 20°C: 4250 mPa s) SS3: SiO ２ / Na ２ O molar ratio = 3.0 (water content at 30 ° C: 61.5 mass%, viscosity at 20 ° C: 175 mPa s)

[0058] <Inorganic fiber> F1: Glass fiber (average fiber diameter 10 μm) <Organic binder> B1: Vinylon fiber (average fiber diameter 5 μm)

[0059] 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 thickness of the wet-formed sheet was 0.6 mm and the basis weight was 120 g / m. ２ It was.

[0060] 3. Preparation of fire spread prevention material (Sample No. 1) Sodium silicate SS1 was impregnated into a wet-formed sheet (inorganic fiber substrate), compressed with a roller, and then dried at 100° C. This produced a fire spread prevention material with a single layer structure in which sodium silicate SS1 was filled into the voids of the wet-formed sheet.

[0061] (Sample No. 2) A single-layer fire prevention material was prepared in the same manner as Sample No. 1, except that sodium silicate SS1 was changed to sodium silicate SS2. (Sample No. 3) A single-layer fire prevention material was prepared in the same manner as Sample No. 1, except that sodium silicate SS1 was changed to sodium silicate SS3.

[0062] (Sample No. 4) The fire spread prevention material obtained in Sample No. 1 was heat-treated by the method described in "4-3. Evaluation of fire spread prevention properties" below, and the resulting fire spread prevention material (the fire spread prevention material after foaming) was designated as Sample No. 4.

[0063] 4. Measurement and Evaluation 4-1. Measurement of Moisture Content For each of sodium silicates SS1 to SS3, a thermogravimetric analyzer ("High Sensitivity Differential Thermobalance STA 2500 Regulus" manufactured by NETZSCH Japan) was used to measure the change in mass up to 1000°C. The measured value at 1000°C was defined as the "amount of solids contained in each of sodium silicates SS1 to SS3," and the moisture content at 30°C for each of sodium silicates SS1 to SS3 was calculated from this value of solids and the measured value of thermogravimetry.

[0064] 4-2. Confirmation of endothermic peak First, a portion of the obtained fire spread prevention material was collected and pulverized to obtain a measurement sample. Next, a thermogravimetric-differential thermal analyzer (TG-DTA) was used to perform DTA measurement on the measurement sample, and a differential thermal curve was obtained 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.

[0065] 4-3. Evaluation of fire spread prevention properties One or two fire spread prevention materials, 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 layered 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 then measured, and the average temperature rise rate from 100°C to 200°C was calculated.

[0066] The results are shown in Table 1 below.

[0067] One or two sheets of each of the fire prevention materials of Samples No. 1 to 4 were 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 glass fiber is sandwiched between two sheets of glass fiber (40°C, 90% RH) and the outer periphery is sealed to produce an outer casing. This produces the same results as above. The same results can also be obtained by using silica fiber, alumina fiber, or alumina-silica fiber instead of glass fiber.

[0068] 1: Fire prevention material 2: Inorganic fiber substrate 3: Layer 5: Exterior body 5a: Sheet material 5b: Sheet material 50: Sealing portion 51: Substrate layer 52: Sealing layer 53: Protective layer SS: Sodium silicate

Claims

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. When the average temperature increase rate from 100°C to 200°C when the fire spread prevention material is heated is V [°C / second], and the thickness of the fire spread prevention material after passing 200°C is Da [mm], a fire spread prevention material in which V × Da is 20 or less.

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

3. In the fire retardant material according to claim 1 or claim 2, the sodium silicate has an SiO ２ / Na ２ O molar ratio of 3.3 or less. Fire retardant material.

4. The fire spread prevention material according to any one of claims 1 to 3, wherein the sodium silicate has a viscosity of 100 mPa·s or more at 20°C.

5. In the fire retardant material according to any one of claims 1 to 4, the constituent material of the inorganic fiber is silica (SiO ２ ), and alumina (Al ２ O ３ ), and the fire retardant material contains at least one selected from the group consisting of these.

6. The fire spread prevention material according to any one of claims 1 to 5, wherein the inorganic fiber base material is a wet-laid sheet.

7. The fire spread prevention material according to any one of claims 1 to 6, wherein the sodium silicate is unevenly distributed on one surface side of the inorganic fiber base material or is impregnated in the inorganic fiber base material.

8. The fire spread prevention material according to any one of claims 1 to 7, wherein the total thickness of the inorganic fiber base material and the sodium silicate is 5 mm or less.

9. The fire spread prevention material according to any one of claims 1 to 8, further comprising an outer package for housing the inorganic fiber base material and the sodium silicate.

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

11. The fire spread prevention material according to any one of claims 1 to 10, which is disposed and used between two adjacent battery cells of a battery pack including two or more battery cells.

12. A battery pack comprising: two or more battery cells; and the fire spread prevention material according to any one of claims 1 to 11 disposed between the adjacent battery cells.

13. An automobile comprising: an automobile body; and the battery pack according to claim 12 mounted on the automobile body.

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