Airtight flame protective cover as well as preparation method and application thereof

Abstract

The invention discloses an airtight flame protective cover and a preparation method and application thereof, and belongs to the technical field of preparation of automobile spare parts, the airtight flame protective cover comprises a multilayer structure embedded with thermosetting resin, and at least one layer in the multilayer structure is a fiber layer containing inorganic fibers and / or filaments; inorganic nanoparticles are combined on the fiber layer and are attached to the surfaces of the inorganic fibers and / or the filaments; the inorganic nanoparticles are selected from at least one of metal oxides, metal hydroxides and silicon dioxide. The thermosetting resin is impregnated in the multi-layer structure, so that the protective cover has air tightness; the airtight flame protective cover achieves airtightness through impregnation of thermosetting resin, and airflow, flames and high-temperature gas can be prevented from spreading among layers. Through the unique multi-layer structure and material selection, on the premise that the excellent protection performance of the protective cover is guaranteed, light-weight packaging is achieved, the forming flexibility is high, and the protective cover can be widely applied to electric automobiles and fixed energy storage systems.

Description

Technical Field

[0001] This invention belongs to the field of battery safety protection technology, specifically relating to an airtight flame shield and its preparation method and application. It is mainly used to resist the jet flames and hot particles generated during battery thermal runaway, providing sufficient time for personnel to escape and for safety protection. Background Technology

[0002] The core power source of pure electric vehicles is the battery system, which consists of multiple battery cells encapsulated in a casing, typically located below the passenger compartment. Similar battery casings are also widely used in stationary energy storage systems to store electrical energy generated by solar power plants, wind power plants, and other similar systems. These batteries are mostly lithium-ion batteries, which are highly susceptible to internal temperature rise and thermal runaway when subjected to mechanical abuse (such as impact or puncture), thermal abuse (such as overheating), or electrical abuse (such as overcharging).

[0003] Battery thermal runaway has distinct developmental stages: when the temperature exceeds 120°C, the chemical barriers within the battery begin to degrade, and the intensified chemical reactions lead to a continuous rise in temperature; when the temperature reaches approximately 260°C, the battery enters a severe thermal runaway state, with the temperature soaring to 800°C, accompanied by jet flames and hot particles ejected from the battery vents. Such thermal runaway events are extremely dangerous whether they occur while a vehicle is in motion or within a stationary energy storage facility, thus requiring reliable protective devices to slow the spread of the disaster and buy time for the safe evacuation of personnel.

[0004] Current battery protection primarily relies on flame shields, which are divided into two categories: battery cell-insulated heat shields and external jet flame shields. External jet flame shields need to withstand the impact of jet flames and hot particles during thermal runaway. However, the aluminum, plastic, or composite materials commonly used in current battery casings cannot withstand these extreme conditions and will be penetrated within seconds. The most advanced thermal runaway shielding layer currently uses a thick mica layer, but experiments show that a 1mm thick mica shield will be perforated within 100 seconds under continuous high-temperature flames at 1200℃ and oxide jets. Mica is a dense material, and its protective performance can only be improved by increasing its thickness. However, the installation space in the battery casing is limited, preventing further thickening, and increasing the thickness would significantly increase the overall weight of the battery, affecting the device's range or installation flexibility.

[0005] Therefore, the industry urgently needs a new type of airtight flame shield that has protective performance no less than that of existing mica shields, and is lighter, requires less installation space, can adapt to the design requirements of different battery casings, can be molded into any shape, and preferably can be integrated into other components of the battery cover or battery casing. Summary of the Invention

[0006] To address the shortcomings of the existing technologies, this application provides an airtight flame shield, its preparation method, and its application. Through a unique multi-layer structure and material selection, the shield achieves lightweight and small-volume packaging while ensuring excellent protective performance. It also offers high molding flexibility and can be widely used in electric vehicles and stationary energy storage systems, solving the problems of large weight, high installation space requirements, and limited protection time of existing mica shields.

[0007] The technical solution adopted in this invention is as follows: An airtight flame shield includes a multi-layer structure embedded with thermosetting resin, wherein at least one layer of the multi-layer structure is a fiber layer containing inorganic fibers and / or filaments. Inorganic nanoparticles are bonded to the fiber layer, and the inorganic nanoparticles are attached to the surface of the inorganic fibers and / or filaments. The inorganic nanoparticles are selected from at least one of metal oxides, metal hydroxides, and silicon dioxide. The thermosetting resin is impregnated in the multilayer structure to make the protective cover airtight; The airtight flame shield achieves airtightness through impregnation with thermosetting resin, which can block the spread of airflow, flame and high-temperature gas between layers.

[0008] Preferably, the inorganic nanoparticles are selected from at least one of magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum trihydrate, calcium oxide, calcium hydroxide, titanium dioxide, zinc oxide, silicon dioxide, potassium oxide, and iron oxide; the inorganic nanoparticles are gaseous oxides or pyrogenic oxides.

[0009] Preferably, the average particle size of the inorganic nanoparticles is less than 1 μm, and the weight of the inorganic nanoparticles accounts for 0.5-50% of the weight of the fiber layer, preferably 1-45%; the weight calculation of the fiber layer does not include the weight of the inorganic nanoparticles bonded to it.

[0010] Preferably, the fiber layer is a mechanically bonded fiber layer, and the mechanical bonding method includes at least one of weaving, stitching, knitting or needle-punched felt; The inorganic fibers and / or filaments are selected from one or more combinations of glass, basalt, aramid, carbon, ceramics, mineral-based fibers, oxidized polyacrylonitrile fibers, and steel fibers; wherein the glass fibers and / or filaments have a temperature resistance of not less than 600℃, preferably not less than 1000℃, and most preferably not less than 1200℃.

[0011] Preferably, it further includes flame-retardant reinforcing particles with a size greater than 1 μm, wherein the flame-retardant reinforcing particles are indirectly bonded to the fibers and / or filaments of the fiber layer through the inorganic nanoparticles, and the inorganic nanoparticles play a bonding role. The flame-retardant reinforcing particles are selected from at least one of natural mica, synthetic mica, kaolinite, mullite, vermiculite, basalt, calcium silicate, and hollow glass beads; the total weight of the inorganic nanoparticles and flame-retardant reinforcing particles accounts for 1-60% of the weight of the fiber layer, preferably 2-55%; the weight calculation of the fiber layer does not include the weight of the inorganic nanoparticles and flame-retardant reinforcing particles bonded to it.

[0012] Preferably, the thermosetting resin is selected from at least one of polyurethane, polyisocyanurate, polyamide, phenolic resin, epoxy resin, silicone resin, unsaturated polyester resin, and vinyl resin; the thermosetting resin further comprises a flame retardant, which is selected from one or more combinations of phosphate-based flame retardants and brominated flame retardants.

[0013] Preferably, the multilayer structure comprises multiple fiber layers, at least one of which is a mechanically bonded fiber layer loaded with the inorganic nanoparticles, and the multiple fiber layers may include spacer layers not loaded with inorganic nanoparticles; the areal weight of the fiber layers is 10-1200 g / m². 2 Preferred size: 50-800g / m 2 More preferably 100-500g / m 2 The thickness of the protective cover is 0.5-5mm, preferably 1-3mm.

[0014] This invention also discloses a method for preparing an airtight flame shield, comprising the following steps: Step 1: Provide a mechanically bonded fiber layer made of inorganic fibers; Step 2: Prepare a sol containing inorganic nanoparticles of metal oxides and / or metal hydroxides and / or silica; Step 3: Impregnate the mechanically bonded fiber layer obtained in Step 1 with the sol obtained in Step 2, so that the inorganic nanoparticles adhere to the fiber and / or filament surface of the fiber layer to form a protective barrier. Step 4: Dry the impregnated fiber layer by placing it at room temperature for 24 hours and then drying it in a 120°C oven for 4 hours; or by other room temperature, high temperature and forced airflow drying methods. Step 5: Combine the fiber layers processed in Steps 1-4 with one or more additional fiber layers to form a multilayer structure; the additional fiber layers are spacers made of inorganic fibers, which may or may not contain mechanical binders and are not loaded with nanoparticles. Step Six: Impregnate the multi-layer structure obtained in Step Five with thermosetting resin. After impregnation, it can be compressed and molded into a protective cover or battery casing.

[0015] Preferably, in step two, flame-retardant reinforcing particles with a particle size of 1-80 μm are added to the sol containing inorganic nanoparticles to form a dispersion system of inorganic nanoparticles and flame-retardant reinforcing particles. In step three, the dispersion system is impregnated with an inorganic fiber layer. Inorganic nanoparticles adhere to the fiber surface to form a protective barrier, while flame-retardant reinforcing particles are indirectly bonded to the fiber to form double protection.

[0016] The present invention also discloses the application of an airtight flame shield in a battery housing, the battery housing including a battery tray, a battery cover and the aforementioned airtight flame shield; the battery tray is used to accommodate multiple battery cells; the airtight flame shield is installed on the inside of the battery cover or used directly as the battery cover; Alternatively, the battery cell may vent towards the battery tray, and the airtight flame shield may be installed inside the battery tray or used directly as the battery tray.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects: 1. Excellent Protective Performance: The inorganic nanoparticles used in this technical solution form a stable barrier due to their own thermal stability, blocking heat flow intrusion, withstanding the thermal shock of flames, and inhibiting combustion; some inorganic nanoparticles undergo endothermic reactions such as dehydration and decomposition, reducing combustion energy and further inhibiting combustion; the gases released by the decomposition of inorganic substances reduce the concentration of combustible gases and oxygen, playing a flame-retardant role; thermosetting resin fully impregnates the multi-layer structure to form an airtight layer, preventing the spread of flames and high-temperature gases between layers; the resin melts under the action of flames and then rapidly carbonizes, forming an additional heat insulation medium; the mechanically bonded fiber layer structure enhances the resistance to disintegration, reduces the formation of pores, and delays flame penetration; through the multiple flame-retardant effects of the inorganic nanoparticles, the structural stability of the mechanically bonded fiber layer, and the airtight packaging of the thermosetting resin, a synergistic technical effect is achieved, which can effectively resist jet flames and thermal particle impacts above 1200℃, and the protection time is better than that of existing mica protective covers; 2. Lightweight and compact: Compared with traditional mica protective covers, this invention uses lightweight materials and optimized structure, making it lighter in weight and only 0.5mm-5mm thick while maintaining the same protective performance, thus meeting the space constraints of the battery casing. 3. High molding flexibility: It can be molded into any shape to adapt to different battery casing design requirements. It can be integrated into battery cover, battery tray or used as an independent protective device. 4. Multifunctional integration: It combines airtightness, flame retardancy, and heat insulation, which can not only prevent environmental factors (condensation, rainwater, dirt) from entering the battery, but also delay the spread of thermal runaway, providing sufficient time for personnel to escape and for equipment protection. 5. Wide range of applications: It is suitable for battery systems of mobile devices such as electric vehicles, trucks, and light commercial vehicles, as well as stationary energy storage systems such as solar power plants, wind power plants, and building energy storage, and has wide applicability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the fiber layer structure of this invention application; Figure 2 This is a schematic cross-sectional view of the airtight flame shield of this invention. Figure 3 This is a schematic diagram of the battery casing structure of the present invention, which includes an airtight flame shield.

[0019] Reference numerals: 1. Fiber layer; 1'. First fiber layer; 1''. Second fiber layer; 2. Inorganic fiber and / or filament; 3. Inorganic nanoparticles; 4. Flame-retardant reinforcing particles; 5. Thermosetting resin; 6. Airtight flame shield; 7. Battery casing; 8. Battery cover; 9. Battery tray; 10. Battery cell. Detailed Implementation

[0020] The present invention will be further described in detail below with reference to the embodiments. It should be understood that the following embodiments are only for explanation and illustration of the present invention, but do not limit the present invention to these specific embodiments, and do not limit the scope of the present invention in any way.

[0021] Example 1: As Figure 1 As shown, this invention discloses an airtight flame shield, comprising a multilayer structure embedded with thermosetting resin, wherein at least one layer of the multilayer structure is a fiber layer 1 containing inorganic fibers and / or filaments; inorganic nanoparticles are bonded to the fiber layer 1, and the inorganic nanoparticles are attached to the surface of the inorganic fibers and / or filaments; the inorganic nanoparticles are selected from at least one of metal oxides, metal hydroxides, and silicon dioxide. Specifically, the inorganic nanoparticles are selected from at least one of magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum trihydrate, calcium oxide, calcium hydroxide, titanium dioxide, zinc oxide, silicon dioxide, potassium oxide, and iron oxide; the inorganic nanoparticles are gaseous oxides or pyrogenic oxides, such as gaseous alumina or gaseous silicon dioxide, or combinations of such oxides and / or hydroxides. The average particle size of the inorganic nanoparticles is less than 1 μm, and the weight of the inorganic nanoparticles accounts for 0.5-50% of the weight of the fiber layer, preferably 1-45%; the weight calculation of the fiber layer does not include the weight of the inorganic nanoparticles bonded to it. Nanoparticles, or nanoparticles in general, are defined as particles with an average diameter of less than 1 μm. When nanoparticles are applied to the fibers and / or filaments of a fiber layer, they may form clusters, but this does not affect the layer's function as an in-situ fire barrier. For example, the areal weight of the fiber layer (excluding the weight of the nanoparticles bonded to its fibers and / or filaments) is 300 g / m². 2 The additional weight of the nanoparticles attached to its fibers and / or filaments is 30 g / m. 2The weight of inorganic nanoparticles accounts for 10% of the weight of the fiber layer; the area weight of nanoparticles attached to the fibers and / or filaments of the fiber layer can be measured by weighing the layer before and after processing to ensure that the nanoparticles are bonded to their fibers and / or filaments. By using nano-oxide particles, good coverage of the fibers and / or filaments of the fiber layer can be achieved with less weight.

[0022] This invention achieves airtightness by impregnating a multi-layered structure with a thermosetting resin. This airtight flame shield, through the impregnation with the thermosetting resin, effectively prevents the spread of airflow, flames, and high-temperature gases between layers. The thermosetting resin is selected from at least one of polyurethane, polyisocyanurate, polyamide, phenolic resin, epoxy resin, silicone resin, unsaturated polyester resin, and vinyl resin.

[0023] Thermosetting resins also contain flame retardants. Although flame retardants are burned up in the early stages of battery failure leading to thermal runaway, the use of flame retardants can reduce the formation of fire or smoke, thereby extending the total time before the airtight flame shield fails. The flame retardant is selected from one or more combinations of phosphate-based flame retardants and brominated flame retardants. Among them, the phosphate-based flame retardant can be TCPP (tris(2-chloroisopropyl) phosphate) or TEP (triethyl phosphate).

[0024] The fiber layer of this invention is a mechanically bonded fiber layer, in which fibers and / or filaments are mechanically connected to each other. The mechanical bonding method includes at least one of weaving, stitching, knitting, or needle-punched felting, essentially where the fibers and / or filaments are mechanically bonded within the overall structure of the fiber layer. More preferably, mechanically bonded inorganic fiber mats or felts can be prepared by stitching or needle-punched felting layers, wherein the needle-punching process is sufficient to form an entangled fiber web. This entanglement, combined with enhanced fiber friction, allows the material to gain more exposure time before being subjected to jet flames and burned through. In the absence of a fiber layer with no mechanical bonding between fibers, the fibers are more easily pushed aside or moved to one side by gas pressure, and heat flow or jets can more easily penetrate between the fibers, which reduces the flame protection performance of inorganic fibers within an airtight flame shield. Therefore, the use of a mechanically bonded fiber layer makes the shield more durable, thereby extending the time before burn-through.

[0025] The inorganic fibers and / or filaments used in the protective cover of this invention are selected from one or more combinations of glass, basalt, aramid, carbon, ceramics, mineral-based fibers, oxidized polyacrylonitrile fibers, and steel fibers. For glass fibers and / or filaments, after high-temperature treatment, their temperature resistance is not less than 600°C, preferably not less than 1000°C, and most preferably not less than 1200°C.

[0026] The fiber layer of this invention also includes flame-retardant reinforcing particles with a size greater than 1 μm, which have heat resistance and / or flame-retardant properties. The flame-retardant reinforcing particles are indirectly bonded to the fibers and / or filaments of the fiber layer through inorganic nanoparticles, which act as a binder. The flame-retardant reinforcing particles are selected from at least one of natural mica, synthetic mica, kaolinite, mullite, vermiculite, basalt, calcium silicate, and hollow glass beads; natural mica can be pyrophyllite, muscovite, phlogopite, or biotite with larger or coarser particle sizes; synthetic mica can be fluorite or fluorinated phlogopite, kaolinite, mullite, and vermiculite.

[0027] The total weight of inorganic nanoparticles and flame-retardant reinforcing particles accounts for 1-60% of the weight of the fiber layer, preferably 2-55%; the weight calculation of the fiber layer does not include the weight of the inorganic nanoparticles and flame-retardant reinforcing particles bonded to it. An adhesive material is used to bond the particulate material and the inorganic fibers and / or filaments. The adhesive material can be an organic adhesive, such as one of polyvinyl butyral, polyvinyl acetate, polyvinylidene fluoride, polyvinyl alcohol polyvinylidene chloride, polyvinyl fluoride, polyvinylpyrrolidone, ethylene-vinyl acetate copolymer, epoxy resin, polyurethane, or phenolic resin. This organic adhesive material has good film-forming properties, completely or partially encapsulating the fibers and bonding them to the fibers and / or filaments.

[0028] Figure 1 This is the fireproof cover structure of Embodiment 1 of the present invention; Figure 1 The structure consists of: 1. Fiber layer; 2. Inorganic fibers and / or filaments; 3. Inorganic nanoparticles; 4. Flame-retardant reinforcing particles; and 5. Thermosetting resin. In fiber layer 1, inorganic nanoparticles 3 are bonded to the surface of inorganic fibers and / or filaments 2, and flame-retardant reinforcing particles 4 are bonded to the fiber surface through inorganic nanoparticles 3, and are integrally embedded in thermosetting resin 5.

[0029] Example 2: Figure 2 As shown, based on Embodiment 1, the airtight flame shield in this embodiment has a multi-layer structure, which includes multiple fiber layers. At least one of the multiple fiber layers is a mechanically bonded fiber layer loaded with inorganic nanoparticles and flame-retardant reinforcing particles (the same structure and composition as in Embodiment 1). The multiple fiber layers may include spacer layers that are not loaded with inorganic nanoparticles. Spacer layers are respectively provided on the upper and lower surfaces of the mechanically bonded fiber layers. Each spacer layer includes inorganic fibers and / or filaments.

[0030] The protective shield comprises different fiber layers, each with different types of nanoscale particles bonded to its fibers and / or filaments to achieve different performance and technical effects within the same shield, contributing to improved effectiveness of the airtight flame shield itself. For example, an airtight flame shield may include a combination of fiber layers with titanium dioxide nanoparticles bonded to its fibers and / or filaments, fiber layers with zinc oxide nanoparticles, and fiber layers with alumina nanoparticles (examples not shown in the figure). The titanium dioxide nanoparticle fiber layer facilitates charring, the zinc oxide nanoparticle fiber layer helps suppress smoke, and the alumina nanoparticle fiber layer provides thermal insulation.

[0031] A fiber layer loaded with nanoparticles bonded to its fibers and / or filaments, and a mechanically bonded fiber layer, can be used alternately with a spacer layer containing inorganic fibers and / or filaments without nanoparticles to enhance the flame and heat barrier effect of adjacent fiber layers or layers loaded with nanoparticles and mechanically bonded. For spacers, fibers without bonded nanoparticles can be mechanically bonded; for example, glass fiber mat layers and / or woven fabrics and / or continuous filament mats and / or chopped strand mats can all be used as spacers.

[0032] The areal weight of the fiber layer in this invention is 10-1200 g / m². 2 Preferred size: 50-800g / m 2 More preferably 100-500g / m 2 The protective cover of the present invention can achieve its technical function using a material much lighter than mica commonly used in existing flame shields. The thickness of the protective cover of the present invention is 0.5-5 mm, preferably 1-3 mm; the protective cover of the present invention can achieve its fireproof function with a very small thickness.

[0033] The airtight flame shield of the present invention comprises a multi-layered structure embedded in a thermosetting resin, thereby forming a jet flame shield with excellent airtightness. Airtightness is defined as an impermeable airflow layer. By fully impregnating the multi-layered structure with thermosetting resin, the flame-retardant layer completely blocks airflow, thereby preventing the spread of flame and / or high-temperature gases between layers and preventing premature heating of the layers within the jet flame shield. Furthermore, the thermosetting adhesive, through its fibrous structure attached to each layer, does not drip when melted under flame, but rapidly carbonizes, forming charred deposits around the fibers and on the layer surfaces. These deposits serve as an additional heat-insulating medium.

[0034] Figure 1 This is the fireproof cover structure of Embodiment 2 of the present invention; Figure 2The structure consists of: 1. Fiber layer (loaded with nanoparticles); 1', first fiber layer; 1'', second fiber layer; 2. Inorganic fibers and / or filaments; 3. Inorganic nanoparticles; 4. Flame-retardant reinforcing particles; 5. Thermosetting resin; 6. Airtight flame shield. In fiber layer 1, inorganic nanoparticles 3 are bonded to the surface of inorganic fibers and / or filaments 2, and flame-retardant reinforcing particles 4 are bonded to the fiber surface through inorganic nanoparticles 3; the first fiber layer 1' and the second fiber layer 1'' are respectively disposed on both sides of fiber layer 1, and the multiple fiber layers are embedded in thermosetting resin 5 to form an integral airtight flame shield 6.

[0035] Example 3: As Figure 3 As shown, based on the protective cover structures of Embodiments 1 and 3, this embodiment of the invention discloses the application of the above-mentioned airtight flame shield in a battery housing. The battery housing 7 includes a battery tray 9, a battery cover 8, and an airtight flame shield 6; the battery tray 9 is used to accommodate multiple battery cells 10. The airtight flame shield 6 is installed inside the battery cover 8 or used directly as a battery cover; or the battery cells 10 exhaust towards the battery tray 9, and the airtight flame shield 6 is installed inside the battery tray 9 or used directly as a battery tray 9.

[0036] The airtight flame shield of this invention can be installed as a stand-alone protective device on any surface near or directly opposite the explosion-proof port of the battery cell and / or battery module, an area more prone to jet flames. This shield can be used in storage enclosures for battery cells and / or modules, either as a fixed solution or integrated into electric vehicles. The airtight flame shield of this invention can also be manufactured and used as a component of the battery casing, for example, as any wall panel or cover, as a partition between the battery casing and the passenger compartment, or as part of the vehicle body. Alternatively, it can be used as a stand-alone panel to isolate the battery and / or battery cells and / or battery modules when needed, such as in the event of a mechanical impact like a vehicle collision. It can also be used in stationary battery energy storage systems or energy storage containers, such as those for electricity generated by power plants, solar panels, or wind turbines, and stationary energy storage in buildings.

[0037] Example 4: A method for preparing an airtight flame shield based on Examples 1-3, comprising the following steps: Step 1: Provide a mechanically bonded fiber layer made of inorganic fibers; Step 2: Prepare a sol containing inorganic nanoparticles of metal oxides and / or metal hydroxides and / or silica; Step 3: Impregnate the mechanically bonded fiber layer obtained in Step 1 with the sol obtained in Step 2, so that the inorganic nanoparticles adhere to the fiber and / or filament surface of the fiber layer to form a protective barrier. Step 4: Dry the impregnated fiber layer by placing it at room temperature for 24 hours and then drying it in a 120°C oven for 4 hours; or by other room temperature, high temperature and forced airflow drying methods. Step 5: Combine the fiber layers processed in Steps 1-4 with one or more additional fiber layers to form a multilayer structure; the additional fiber layers are spacers made of inorganic fibers, which may or may not contain mechanical binders and are not loaded with nanoparticles. Step Six: Impregnate the multi-layer structure obtained in Step Five with thermosetting resin. After impregnation, it can be compressed and molded into a protective cover or battery casing.

[0038] In step two, flame-retardant reinforcing particles with a particle size of 1-80 μm can be added to the sol containing inorganic nanoparticles to form a dispersion system of inorganic nanoparticles and flame-retardant reinforcing particles. In step three, the dispersion system is impregnated with a fiber layer made of inorganic fibers. The inorganic nanoparticles adhere to the fiber surface to form a protective barrier, while the flame-retardant reinforcing particles are indirectly bonded to the fibers to form double protection.

[0039] Based on the airtight flame shields and their preparation methods and applications in Examples 1-4, the following detailed embodiments are provided for further explanation.

[0040] Specific Embodiment 1: The airtight flame shield in this embodiment contains 5 stacked fiber layers, all impregnated in polyurethane thermosetting resin that meets the V0 flame retardant standard in UL94.

[0041] Core fiber layer: composed of 300g / m² area weight 2 It is made of glass fiber nonwoven fabric, with nano-alumina particles bonded to the fiber surface, and mica particles with an average size of 75 micrometers are bonded to the nano-alumina particles; after drying, the area weight of the core fiber layer is 334 g / m². 2 The combined area weight of nano-alumina particles and mica particles increased by 11.33%.

[0042] The other four fiber layers: all have an area weight of 400 g / m² 2 The glass fiber nonwoven fabric has two layers arranged on one side of the core layer and two other layers arranged on the other side of the core layer, with the core layer located in the middle of the five-layer structure.

[0043] The protective shield obtained in this embodiment has a total thickness of 1.1-1.3 mm. To evaluate its effectiveness, a "torch and gravel" performance test was conducted on the jet flame protective shield. The flame temperature was 1200±50℃, and the gravel flow rate was 1.50±3 g / s. The test cycle consisted of "15 seconds of flame, 5 seconds of flame and gravel", with each cycle lasting 20 seconds. The protective shield could withstand 10 cycles without perforation, demonstrating excellent protective performance.

[0044] Specific embodiment 2: The airtight flame shield of this embodiment contains 6 stacked fiber layers, all impregnated in polyurethane thermosetting resin that meets the V0 flame retardant standard in UL94.

[0045] Core fiber layer: Two fiber layers, each with an area weight of 300g / m² 2 Made of glass fiber nonwoven fabric, using PVDF as a binder (30% by weight of alumina particles) to bond alumina particles with an average size of 20μm to the fiber surface; after drying, the area weight of each core fiber layer is 345g / m². 2 Alumina particles increase the area weight by 15%.

[0046] The other four fiber layers: all have an area weight of 400 g / m² 2 The glass fiber plain weave fabric is arranged in layers: one layer on one side of two core layers, two layers in the middle of two core layers, and one layer on the other side. The core layer is located in the middle of the six-layer structure. The total thickness of the protective shield obtained in this embodiment is 1.4-1.6 mm. Using the same "torch and gravel" test method as in Specific Embodiment 1, the protective shield can withstand 13 cycles without perforation, demonstrating excellent protection against jet flames.

[0047] The inorganic nanoparticles used in this invention form a stable barrier due to their own thermal stability, blocking heat flow intrusion, withstanding the thermal shock of flames, and inhibiting combustion. Some inorganic nanoparticles undergo endothermic reactions such as dehydration and decomposition, reducing combustion energy and further inhibiting combustion. The gases released by the decomposition of inorganic substances reduce the concentration of combustible gases and oxygen, playing a flame-retardant role. Thermosetting resin fully impregnates the multi-layer structure to form an airtight layer, preventing the spread of flames and high-temperature gases between layers. The resin melts under the action of flames and then rapidly carbonizes, forming an additional heat insulation medium. The mechanically bonded fiber layer structure enhances the resistance to disintegration, reduces the formation of pores, and delays flame penetration. Through the multiple flame-retardant effects of the inorganic nanoparticles, the structural stability of the mechanically bonded fiber layer, and the airtight packaging of the thermosetting resin, a synergistic technical effect is achieved, which can effectively resist jet flames and thermal particle impacts above 1200°C, and the protection time is better than that of existing mica protective covers.

[0048] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An airtight flame shield, characterized in that, It includes a multilayer structure embedded with thermosetting resin, wherein at least one layer of the multilayer structure is a fiber layer containing inorganic fibers and / or filaments; Inorganic nanoparticles are bonded to the fiber layer, and the inorganic nanoparticles are attached to the surface of the inorganic fibers and / or filaments. The inorganic nanoparticles are selected from at least one of metal oxides, metal hydroxides, and silicon dioxide. The thermosetting resin is impregnated in the multilayer structure to make the protective cover airtight; The airtight flame shield achieves airtightness through impregnation with thermosetting resin, which can block the spread of airflow, flame and high-temperature gas between layers.

2. The airtight flame shield according to claim 1, characterized in that, The inorganic nanoparticles are selected from at least one of magnesium oxide, magnesium hydroxide, aluminum oxide, aluminum trihydrate, calcium oxide, calcium hydroxide, titanium dioxide, zinc oxide, silicon dioxide, potassium oxide, and iron oxide; the inorganic nanoparticles are gaseous oxides or pyrogenic oxides.

3. The airtight flame shield according to claim 1, characterized in that, The inorganic nanoparticles have an average particle size of less than 1 μm, and the weight of the inorganic nanoparticles accounts for 0.5-50% of the weight of the fiber layer, preferably 1-45%; the weight calculation of the fiber layer does not include the weight of the inorganic nanoparticles bonded to it.

4. The airtight flame shield according to claim 1, characterized in that, The fiber layer is a mechanically bonded fiber layer, and the mechanical bonding method includes at least one of weaving, stitching, knitting or needle-punched felt. The inorganic fibers and / or filaments are selected from one or more combinations of glass, basalt, aramid, carbon, ceramics, mineral-based fibers, oxidized polyacrylonitrile fibers, and steel fibers; wherein the glass fibers and / or filaments have a temperature resistance of not less than 600℃, preferably not less than 1000℃, and most preferably not less than 1200℃.

5. The airtight flame shield according to claim 1, characterized in that, It also includes flame-retardant reinforcing particles with a size greater than 1 μm, which are indirectly bonded to the fibers and / or filaments of the fiber layer through the inorganic nanoparticles, and the inorganic nanoparticles play a bonding role. The flame-retardant reinforcing particles are selected from at least one of natural mica, synthetic mica, kaolinite, mullite, vermiculite, basalt, calcium silicate, and hollow glass beads; the total weight of the inorganic nanoparticles and flame-retardant reinforcing particles accounts for 1-60% of the weight of the fiber layer, preferably 2-55%; the weight calculation of the fiber layer does not include the weight of the inorganic nanoparticles and flame-retardant reinforcing particles bonded to it.

6. The airtight flame shield according to claim 1, characterized in that, The thermosetting resin is selected from at least one of polyurethane, polyisocyanurate, polyamide, phenolic resin, epoxy resin, silicone resin, unsaturated polyester resin, and vinyl resin; the thermosetting resin further comprises a flame retardant, which is selected from one or more combinations of phosphate-based flame retardants and brominated flame retardants.

7. The airtight flame shield according to claim 1, characterized in that, The multilayer structure comprises multiple fiber layers, at least one of which is a mechanically bonded fiber layer loaded with the inorganic nanoparticles, and the multiple fiber layers may include spacer layers without inorganic nanoparticles loaded; the areal weight of the fiber layers is 10-1200 g / m². 2 Preferred size: 50-800g / m 2 More preferably 100-500g / m 2 The thickness of the protective cover is 0.5-5mm, preferably 1-3mm.

8. A method for preparing an airtight flame shield as described in any one of claims 1-7, characterized in that, Includes the following steps: Step 1: Provide a mechanically bonded fiber layer made of inorganic fibers; Step 2: Prepare a sol containing inorganic nanoparticles of metal oxides and / or metal hydroxides and / or silica; Step 3: Impregnate the mechanically bonded fiber layer obtained in Step 1 with the sol obtained in Step 2, so that the inorganic nanoparticles adhere to the fiber and / or filament surface of the fiber layer to form a protective barrier. Step 4: Dry the impregnated fiber layer by placing it at room temperature for 24 hours and then drying it in a 120°C oven for 4 hours; or by other room temperature, high temperature and forced airflow drying methods. Step 5: Combine the fiber layers processed in Steps 1-4 with one or more additional fiber layers to form a multilayer structure; the additional fiber layers are spacers made of inorganic fibers, which may or may not contain mechanical binders and are not loaded with nanoparticles. Step Six: Impregnate the multi-layer structure obtained in Step Five with thermosetting resin. After impregnation, it can be compressed and molded into a protective cover or battery casing.

9. The method for preparing the airtight flame shield according to claim 8, characterized in that, In step two, flame-retardant reinforcing particles with a particle size of 1-80 μm are added to the sol containing inorganic nanoparticles to form a dispersion system of inorganic nanoparticles and flame-retardant reinforcing particles. In step three, the dispersion system is impregnated with an inorganic fiber layer. Inorganic nanoparticles adhere to the fiber surface to form a protective barrier, while flame-retardant reinforcing particles are indirectly bonded to the fiber to form double protection.

10. The application of an airtight flame shield as described in any one of claims 1-7 in a battery casing, characterized in that, The battery housing includes a battery tray, a battery cover, and an airtight flame shield (6) as described in any one of claims 1-7; the battery tray (9) is used to accommodate a plurality of battery cells (10); the airtight flame shield (6) is installed on the inside of the battery cover (8) or is used directly as the battery cover; Alternatively, the battery cell (10) may vent towards the battery tray (9), and the airtight flame shield (6) may be installed on the inside of the battery tray (9) or used directly as the battery tray (9).

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