Flame shield for electric vehicle battery and battery case including same

Abstract

A flame shield, in particular for a battery electric vehicle, comprising at least one refractory layer comprising reinforcing fibers having a melting temperature above 500 DEG C completely embedded in a thermoset matrix material, characterized in that the matrix material comprises at least one of a polyisocyanurate or a polyisocyanurate-polyurethane.

Description

Technical Field

[0001] This invention relates to a flame shield for electric vehicle batteries and a method for manufacturing the same. Furthermore, this invention relates to battery housings including such flame shields. Background Technology

[0002] Electric vehicles are typically powered by rechargeable batteries that provide the electricity needed to drive one or more electric motors that propel the vehicle itself. Batteries generally consist of multiple electrically connected battery cells, which can be organized into battery modules.

[0003] Among different types of rechargeable batteries, lithium-ion batteries, in particular, are widely used in electric vehicles due to their high energy density. For a given battery weight, lithium-ion batteries can guarantee a longer driving range.

[0004] In electric vehicles, batteries are typically installed in an area beneath the vehicle body. Typically, the battery is enclosed in a battery case, which consists of a lower shell (hereinafter referred to as the battery tray, on which the battery is located) and an upper shell (hereinafter referred to as the battery cover or battery lid, which covers the battery from above). Typically, the battery case (especially the battery cover) is made of a metallic material. Aluminum is often used for this purpose due to its advantageous stiffness-to-weight ratio.

[0005] In some cases, the battery can be encapsulated between the vehicle floor and a battery tray, which is directly attached to the vehicle body and the battery sits on top of it. In these cases, the vehicle floor, typically made of aluminum or steel, serves as the battery cover.

[0006] Rechargeable batteries (especially lithium-ion batteries) used for traction in electric vehicles can pose significant safety risks. In cases of mechanical abuse (e.g., impact, puncture) and / or thermal abuse (e.g., overheating) and / or electrical abuse (e.g., overcharging), a short circuit can occur within one or more battery cells, potentially leading to the exothermic decomposition of their chemical components. This causes a rapid rise in their temperature, which can propagate to nearby battery cells, causing them to overheat and creating a cascading effect known as "thermal runaway."

[0007] During thermal runaway, extremely high temperatures can develop inside the battery in a very short time, and the chemical composition of the battery cell can ignite, potentially leading to an explosion in extreme cases. Specifically, thermal runaway in lithium-ion batteries can generate flames with temperatures reaching approximately 900°C. These temperatures are far higher than the melting point of typical battery covers and / or vehicle floor panels made of aluminum.

[0008] Furthermore, as batteries age, their sensitivity to heat and electrical abuse increases, leading to the risk of thermal runaway.

[0009] In the event of thermal runaway, to ensure the safety of passengers in the passenger compartment, the primary and most important priority is to warn them to evacuate the passenger compartment sufficiently early, before unbearable temperatures and / or flames reach it. To this end, the Chinese standard GB38031-2020 requires the battery management system to provide an alarm signal at least 5 minutes (the so-called "escape time") before heat propagation caused by a thermal runaway event (even from a single battery cell) occurs. In addition, to further protect the passenger compartment from high temperatures and / or fire during this "escape time," protective flame shielding is typically applied to the battery cover and / or vehicle floor / body panels, usually on the side facing the battery.

[0010] Existing flame shielding devices typically consist of a thin mica layer adhered to the battery cover and / or the battery-facing side of the vehicle floor panel. Indeed, mica is a very effective flame shielding material with a melting point of approximately 1300°C. However, mica-based flame shielding devices present several challenges.

[0011] Mica is a rather heavy material with a density of 2700 kg / m³. 3 Up to 3000 kg / m 3 Therefore, flame shielding components incorporating mica layers can be very heavy, with an area weight ranging from 2.5 kg / m². 2 Up to 6kg / m 2 This depends on the thickness of the mica layer. The areal weight can even exceed that of a battery cover with flame shielding. This is very detrimental to the driving range of electric vehicles, a feature that is of great concern to end consumers interested in these vehicles.

[0012] In addition, thin mica shielding is very fragile and the risk of breakage increases as the component ages.

[0013] Finally, while mica is a naturally sourced material, its origin and extraction are not without controversy, leading automakers to seek mica-free alternatives with the aim of banning its use in the future.

[0014] The purpose of this invention is to provide a flame shield specifically for battery electric vehicles, which represents an alternative solution to mica-based flame shields, particularly being lighter and less prone to breakage. Summary of the Invention

[0015] The object of the present invention is achieved by the flame shielding for battery electric vehicles according to claim 1, the method for producing such a flame shielding according to claim 14, and the battery housing including such a flame shielding according to claim 16.

[0016] In its main aspect, the present invention relates to a flame shield for battery-electric vehicles, comprising at least one refractory layer comprising reinforcing fibers having a melt temperature above 500°C fully embedded in a thermosetting matrix material, wherein the matrix material comprises at least one of polyisocyanurate or polyisocyanurate-urethane.

[0017] Preferably, the matrix material is based on polyisocyanurate (PIR) and embeds and surrounds the fibers in a manner that makes the resulting refractory layer impermeable to airflow. Reducing or eliminating voids in the layer prevents the leakage of smoke during thermal runaway events, while also allowing flames to find an easier path through the refractory layer. Therefore, for similar reasons, non-foamed PIR is preferred. For example, voids formed by foam bubbles not only create weak points in the refractory layer but also provide trapped air pockets, further fueling the fire. Higher density materials mean less trapped air in the material used.

[0018] The refractory layer according to the invention can withstand the high temperatures generated by open flame and the negative effects of the open flame itself. It has been found that using the refractory layer with PIR according to the invention can prolong the "escape time" and increase the temperature difference between the surface exposed to open flame and the opposite surface.

[0019] The polyisocyanurate according to the invention is typically obtained by reacting a polyurethane-polyisocyanurate forming mixture comprising a polyol and an isocyanate, said mixture being premixed before application. The polyisocyanurate forming mixture typically used in the method of the invention will comprise: at least one polyol component with an average OH value of 300 to 900, each polyol having a functionality of 2 to 6; at least one isocyanate, preferably at least one of a mixture of isomers of diphenylmethane diisocyanate (MDI), polymeric MDI, or a prepolymer thereof; one or more catalysts, including those known in the art that promote polyisocyanurate groups, such as potassium octanoate or potassium acetate; surfactants or stabilizers; release agents and additives, such as fillers, colorants, or rheology modifiers. Suitable polyols may be polyester- or polyether-based.

[0020] In PIR-based matrix materials, standard fillers that do not negatively affect the fire resistance of the flame shield can be used, such as inorganic materials, like barium sulfate or calcium carbonate, chalk, talc, or other non-reactive fillers.

[0021] Polyisocyanurates, as known in the art, comprise the reaction products of polyols and isocyanates. A characteristic of polyisocyanurates, and a distinction from polyurethanes, is the formation of highly thermally stable isocyanurate groups during the reaction. Preferably, the formation of isocyanurate groups is increased, for example, by adjusting the ratio of reactive isocyanate (NCO) groups to reactive hydroxyl (OH) groups. Preferably, the amount of reactive isocyanate (NCO) groups exceeds the amount of reactive hydroxyl (OH) groups, with a preferred ratio of at least 1.8 to 1. Alternatively, the isocyanate / polyol ratio (also known as its index (defined as the ratio of NCO groups to OH groups multiplied by 100)) is greater than 180.

[0022] Surprisingly, by increasing the isocyanurate groups in the PIR-based matrix material, a more thermally stable layer can be produced, which can withstand the direct effects of flame for a long time before the material is burned through.

[0023] Preferably, the refractory layer can withstand an open flame test for at least 10 minutes, preferably at least 15 minutes, and even more preferably at least 20 minutes without being burned through. Surprisingly, within the scope of the claimed protection, burn-through is independent of the layer thickness.

[0024] Furthermore, the final temperature reached after a 10-minute open flame test is one-third of the flame temperature. The advantage of reducing the temperature reached on the opposite side of the flame shield is that, when used between cells, adjacent cells are heated less and will begin to release gas later, thereby reducing the rate of overall thermal runaway events.

[0025] Preferably, the weight of the reinforcing fiber is 20% to 95% of the total weight of the refractory layer, more preferably 40% to 85% of the total weight of the refractory layer, and even more preferably 50% to 70% of the reinforcing fiber based on the total weight of the refractory layer.

[0026] Because of the use of a large amount of fiber compared to PIR-based matrix materials, the total content of PIR-based matrix materials in the product can be very low, and the maximum amount of smoke during flame testing can be minimized.

[0027] The refractory layer comprises reinforcing fibers fully embedded in the PIR-based material according to the invention. To maintain the stability of the flame shield in the event of a runaway event, the fibers need to have a melting temperature of at least 500°C. Preferably, the reinforcing fibers comprise at least one of the following: ceramic fibers, glass fibers, carbon fibers, mineral-based fibers, oxidized polyacrylonitrile fibers, quartz fibers, or mixtures of such fibers.

[0028] The reinforcing fibers can be short fibers, long fibers, endless filaments, or any combination of staple fibers and filaments. The fibers can be provided in any known structure, such as woven or nonwoven structures. The fibers can be lightly bonded using mechanical or chemical methods, such as needle punching, sewing, air-laid, or carding structures. Alternatively, they can be lightly bonded using polymers, resin adhesives, or sol-gel adhesives as known in the art. Adhesives can include polymers such as polyvinyl alcohol, urea-formaldehyde resin, phenolic resin, epoxy resin, silica, or ceramic sol. Thermosetting adhesives are preferred.

[0029] As is known in the art, various sizing agents may also be included on high-temperature fibers. These sizing agents provide a thin surface adhesive layer on, for example, glass or mineral fibers, for adhesion and flowability. Sizing agents may contain flame retardants.

[0030] The advantage of providing lightly bonded fiber layers is that the material can be stored and handled without loss of its structure. Material pads or unidirectional tapes can be used, preferably lightly bonded. Preferably, the fiber material has been pre-shaped into or guided to the final shape of the component before impregnation with the polyisocyanurate mixture. A combination of sandwich material and short fiber core and unidirectional tape can be used, thereby embedding at least one or all layers into a PIR-based matrix material. Optionally, the layers facing away from the open flame source can be embedded in different materials, such as thermosetting or polyurethane materials, or can be used solely through the bonding of the layers without a matrix material.

[0031] According to the present invention, a flame shield may comprise one or more fire-resistant layers, wherein these layers may contain the same material or differ in fiber mixture and / or quantity. Their density and / or thickness may also vary on the surface. The flame shield may be used in partial or complete overlap. The overlapping areas may be designed with staggered joints, overlaps, or tongue and groove joints to achieve, for example, a more seamless coverage over a larger area. The overlapping areas may be sealed with tape or adhesive to secure the fire shield.

[0032] Other devices (such as mounting devices) can be integrated into the flame shield.

[0033] The thickness of the refractory layer is at least 0.25 mm. Depending on the shape and design requirements, as well as the required temperature difference between the sides of the refractory layer, the thickness can be up to 10 mm. Preferably, to reduce the overall weight and minimize the required space, the preferred thickness is 0.5 to 4 mm, more preferably 1 to 3 mm, in most cases.

[0034] The fire-resistant layer can effectively prevent flame burn-through even at a very low thickness. This has the advantage that flame shielding devices including fire-resistant layers can be used in areas with limited space, such as between the surfaces of battery cells and battery casings. Thicker shielding devices may be more beneficial, for example, in situations requiring high bending stiffness.

[0035] The flame shielding member according to any one of the preceding claims, wherein the density of the fire-resistant layer is 1000 kg / m³. 3 Up to 2400 kg / m 3 Optimal 1200kg / m 3 Up to 1800 kg / m 3 .

[0036] The refractory layer according to the present invention may also contain flame-retardant additives as known in the art.

[0037] Flame-retardant additives that can be used in the refractory layer of the present invention include, but are not limited to, chlorinated organic compounds and polymers, brominated organic compounds and polymers, phosphate-functionalized organic compounds and polymers, such as phosphate esters, chloroalkyl phosphate esters, phosphonates, and ammonium salts of phosphoric acid, polyphosphates, sulfuric acid, and hydrochloric acid, or mixtures thereof.

[0038] PIR matrix materials may also contain flame retardant synergists, such as antimony trioxide and other inorganic compounds (e.g., calcium borate, zinc borate, zinc stannate, and zinc hydroxystannate).

[0039] Flame retardant additives and / or flame retardant synergists can be added to PIR-based matrix materials in the form of solid or liquid additives.

[0040] Preferably, the amount of flame retardant additives and / or flame retardant synergists added will not cause the layer thickness to expand by more than 10%. Depending on the type and requirements, the amount of flame retardant and / or flame retardant synergists may account for up to 25% of the polyisocyanurate material.

[0041] The preferred flame retardants and / or flame retardant synergists described above can be applied as a coating to the flame shield or to the fiber.

[0042] PIR-based matrix materials may also include non-fibrous non-combustible fillers to enhance fire resistance and / or further reduce smoke generation, wherein the non-fibrous non-combustible fillers are preferably one of mica, aluminum hydroxide or magnesium hydroxide.

[0043] In cases where the flame shielding element comprises more than one fire-resistant layer of the present invention, these layers may differ in the availability and / or type and / or amount of flame retardant additives and / or flame retardant synergists.

[0044] In its simplest embodiment, the flame shielding element according to the invention may consist of a single fire-resistant layer according to the invention.

[0045] Depending on the design of the area of ​​the flame shield, the flame shield may consist of two or more fire-resistant layers according to the invention, which may partially or completely overlap each other.

[0046] When multiple refractory layers partially or completely overlap or at least contact each other, they can be bonded together by simple adhesive layers or by mechanical means (e.g., clamping). The overlapping portions can be in the form of grooves to form a closed seal when installed in an automobile.

[0047] The flame shield can be molded into any form or design as needed. For example, it can be formed as a simple, basically flat shield to be placed on top or bottom of a battery cell, or it can be formed as a box or cylinder to enclose a cell or a group of cells.

[0048] Flame shielding components can be used to protect areas that may be directly or indirectly exposed to potential fire risks. This may be related to the risk of the main traction battery, but may also be used for other potential fire hazards. The flame shielding components can also be used in other vehicles or areas requiring similar fire resistance.

[0049] The flame shield can be inside and / or outside the battery housing, for example, between the battery housing and the main floor panel of the vehicle, or inside the dashboard or floor components inside the vehicle.

[0050] In more complex embodiments, the flame shield according to the invention may further include a supplementary layer, i.e., a layer different from the fire-resistant layer according to the invention. Such a layer may be included in the flame shield according to the invention to further enhance its flame shielding performance and / or for other purposes, such as enhancing mechanical properties and / or improving processability and / or appearance during production or installation.

[0051] Surprisingly, the refractory layer according to the invention achieves sufficient flame shielding performance required by automotive manufacturers due to the synergistic effect between the reinforcing fibers with a melting temperature exceeding 500°C and the matrix material formed by PIR. On one hand, in addition to imparting dimensional stability to the refractory layer according to the invention, the fibers also conduct heat, distributing it across the entire surface of the layer and acting as an effective heat storage medium. On the other hand, the polyisocyanurate prevents flame propagation through the layer by being fully embedded in the fiber material in a manner that makes the refractory layer impermeable to airflow. Furthermore, by adhering to the reinforcing fibers, the polyisocyanurate does not drip or break upon contact with an open flame and rapidly carbonizes, producing char deposits around the fibers and on the surface of the layer, which act as a further flame barrier.

[0052] To achieve this effect, it is preferable to completely coat the fibers with polyisocyanurate to make them airtight, that is, the fiber layer is soaked in polyisocyanurate so that the polyisocyanurate blocks all the pores between the fibers and tightly surrounds all the fibers contained therein.

[0053] Fire resistance test To determine the fire resistance of the flame shield comprising such a layer or the fire-resistant layer contained in such a flame shield according to the invention, a fire resistance test was used, wherein, in a control experiment, one surface of the material was subjected to an open flame. A flat, square sample of the fire-resistant layer was placed in an open flame such that the surface was exposed to a direct flame at 1100 ± 100 °C.

[0054] The sample is exposed to a flame from one side (often referred to as the "flame side") for a predetermined time. During the test, the temperature change over time at the center of the opposite side of the sample exposed to the flame (often referred to as the "covered side") is measured and recorded using any of the aforementioned measuring devices (such as a digital thermometer or thermocouple).

[0055] Calculate the temperature difference between the flame center temperature on the flame side and the sample center temperature on the covered side. This temperature difference indicates the insulation performance of the refractory layer when exposed to an open flame. (Cover test) The attached figure shows the temperature change over time on the covered side when exposed to a flame at 1100°C ± 100°.

[0056] The component fails when the flame burns through the material before the required time (e.g., at least no earlier than 10 minutes, preferably at least no earlier than 15 minutes, and preferably no earlier than 20 minutes). The sample also fails when the material sags, drips, or deforms excessively during the test.

[0057] If the gas released from the cover side spontaneously combusts during the test, the test can also be considered a failure. Spontaneous combustion on the cover side will be visually obvious, but it will also show a temperature peak on the cover side temperature probe.

[0058] The sample shown in Figure 5 did not burn through, but the experiment was stopped after 10 minutes.

[0059] Thermal particle impact test In the second test measuring durability and fire resistance, a thermal particle impact test was used to measure the mechanical resistance of the flame shield during combustion.

[0060] During the test, the flame was directed at the vertically mounted sample until the flame temperature reached 1200°C. Once 1200°C was reached, silicon carbide particles of 200-500 micrometers in size were sprayed onto the sample in eight separate applications at a pressure of 2 bar, each application lasting 5 seconds. A maximum of 300 mL of particles was added per cycle. The material was then held at 1200°C for 2 minutes before the next round of particle spraying. This process was repeated until failure occurred. The test was stopped upon the appearance of obvious signs of failure. Throughout the test, the temperatures of the front and back sides of the material were measured.

[0061] Surprisingly, the refractory layer according to the invention, comprising chopped fibers fully embedded in the PIR, has passed the test, exhibiting low particle abrasion and showing failure after only 5 minutes at 1200°C, comparable to currently used mica sheets of the prior art. The total failure time could be further increased by using longer fibers or continuous filaments.

[0062] To enhance the protection provided by the flame shielding according to the invention during escape time, the temperature drop on the fire-resistant layer according to the invention, measured in an open flame test without particles, is preferably at least 500°C, more preferably at least 600°C, and even more preferably at least 700°C. Preferably, the temperature on the covered side does not exceed the melting temperature of the metal material (such as aluminum) used in the battery casing and / or vehicle body.

[0063] Preferably, the mechanical properties of the flexural modulus exceed 5000 MPa in the flexural test ISO 178 with a test speed of 10 mm / min and an elastic modulus evaluation range of 0.05-0.25%.

[0064] Also preferably, the flexural strain at the flexural strength in the same test exceeds 2%. This percentage is small compared to polymer layers, but for thermosetting composites, it represents a certain amount of deformation capacity before breakage, which is advantageous compared to more fragile flame shields (such as mica).

[0065] The fracture tensile strength of the flame shield is preferably greater than 100 MPa, and the fracture tensile strain is preferably greater than 1.5%.

[0066] In a preferred embodiment, the reinforcing fiber is in a nonwoven form, comprising one or more layers containing E-glass fibers, which may partially or completely overlap each other. The E-glass fibers are resistant to thermal expansion, which can provide dimensional stability to the layers in the event of temperature fluctuations that may occur during the battery's lifespan. E-glass fibers also provide high mechanical strength and stiffness at low weight, and they can simultaneously exhibit low dielectric constant values, low dielectric loss values, or both. The E-glass fibers may comprise any of silica, alumina, calcium oxide, and boron oxide.

[0067] In another preferred embodiment, the E-glass fiber may be boron-free. Such a boron-free material is called E-CR glass. E-CR glass can provide acid and / or chemical resistance. E-CR glass can also provide enhanced temperature resistance.

[0068] Layers containing E-glass and / or E-CR glass fibers can be formed by any suitable method known in the art, including but not limited to needle punching, air-laid web forming, and wet-laid web forming.

[0069] In a particularly preferred embodiment, the fibrous nonwoven fabric comprises one or more layers of E-glass fibers, wherein each layer is in the form of a chopped-strand mat composed of short E-glass fibers, the chopped-strand mat being bonded together by a small amount of thermosetting adhesive (preferably less than 10% by weight, more preferably less than 5% by weight). The thermosetting adhesive is preferably a phenolic-based resin or an epoxy-based polyester resin. In this embodiment, the length of the E-glass short fibers is preferably 20 mm to 80 mm, more preferably 30 mm to 70 mm, and even more preferably 40 mm to 60 mm.

[0070] In another preferred embodiment, the fibrous nonwoven fabric according to the invention may comprise one or more layers substantially composed of ceramic fiber blankets (hereinafter referred to as "ceramic blankets"). The ceramic blanket layers may provide improved operating strength, enhanced thermal properties, or both. The ceramic blanket layers may exhibit excellent thermal stability, good flexibility, and ease of cutting and shaping. The ceramic blankets may also possess good tear resistance. The ceramic blanket layers may be formed by any suitable method, including but not limited to needle punching.

[0071] The ceramic blanket may be substantially free of binders (e.g., containing about 1% by weight or less of the layer), or even completely free of binders. The ceramic blanket may be formed from inorganic materials, the amount of which is up to about 100% by weight (inclusive) of the layer. For example, the ceramic blanket may include silica, calcium oxide, and magnesium oxide.

[0072] The nonwoven fabric according to the present invention may include one or more layers of glass fibers, which can impart high temperature resistance, thermal stability, abrasion resistance, tear resistance and chemical solvent resistance to the refractory layer according to the present invention.

[0073] The fibrous nonwoven fabric may also include one or more layers comprising organic fibers. The organic fiber-containing layers may contain preferably at least 50% by weight of organic fibers, more preferably at least 75% by weight of organic fibers. This can be used in conjunction with glass fibers. In a preferred embodiment, the fibers may be formed from or comprise organic synthetic thermoplastic polymer resins. For example, the fibers may be polyacrylonitrile fibers. Polyacrylonitrile fibers may be oxidized polyacrylonitrile fibers, such as Ox-PAN, OPAN, or PANOX.

[0074] The fibers contained in the nonwoven fabrics according to the invention may be virgin fibers and / or they may be derived from a recycling process, which may be a post-industrial or post-consumer recycling process.

[0075] For example, the glass fibers contained in the fiber nonwovens according to the invention can be derived from the end-of-life treatment of GFRP (glass fiber reinforced polymer) products such as aircraft and ship hull panels, where thermal (e.g., fluidized bed treatment) and / or chemical treatments separate the glass fibers from the polymer matrix and allow for recycling. In another example, the glass fibers contained in the fiber nonwovens according to the invention can be produced by recycling post-industrial glass waste.

[0076] The flame shielding component according to the present invention can be manufactured using methods known in the art. A preferred manufacturing method may include at least the following steps.

[0077] 1. Reinforcing fibers with a melting point of at least 500°C are provided, preferably in the form of a pad-like or felt-like layer; the fibers may optionally be consolidated by mechanical or chemical bonding. Preferably, the fibers have been pre-shaped to facilitate product molding.

[0078] 2. Applying the polyisocyanurate forming mixture onto the reinforcing fibers. After mixing the polyol and isocyanate components, the polyisocyanurate forming mixture is typically in a viscous fluid form that can be easily poured or sprayed onto the reinforcing fibers, for example, through a mixing head. Mixing and metering can be performed immediately before spreading the polyisocyanurate forming mixture onto the fibers.

[0079] 3. The reinforcing fibers and / or layers thus prepared are thermoformed into the desired shape, preferably by compression molding. The heat of the mold will (further) activate the polyisocyanurate mixture, generating pressure that will cause the polyisocyanurate to impregnate the fiber material, spreading around the fibers and through the pores of the fiber nonwoven fabric, and embedding the fibers into the matrix material; 4. Demold and optionally trim the edges.

[0080] In a variation of the above method, the spreading of the polyisocyanurate forming mixture on the fibrous nonwoven fabric can be carried out directly within a heated mold. This can be advantageous because it reduces the space and time required to produce the flame shielding element according to the invention.

[0081] As described above, this method is very simple compared to the methods required to produce existing mica-based flame shields. Due to the above method, a flame shield consisting of only one refractory layer according to the invention can be obtained. Clearly, this method can be extended to cases where the flame shield according to the invention comprises more than one refractory layer.

[0082] Notably, the above method allows for the creation of refractory layers with three-dimensional shapes (i.e., shapes substantially different from planar shapes). This design flexibility is a result of the refractory layer composition (i.e., fibrous nonwovens and polyisocyanurate, both of which have high formability). This is advantageous compared to existing mica-based flame shields, which, due to the fragility of mica, cannot conform to the shape of a battery cover with strong curvature.

[0083] Another aspect of the invention relates to a battery housing or battery box for a battery (particularly a lithium-ion battery) for an electric vehicle, comprising a battery cover and a battery tray, wherein a flame shielding element according to the invention is applied to the battery cover and / or battery tray on the side facing the battery.

[0084] The design flexibility of the flame shield according to the invention allows for conforming to complex three-dimensional shapes, such as battery covers and / or battery trays, even in areas where the shape is far from planar, such as where it exhibits strong curvature and / or features (e.g., ribs, embossments, etc.). This is advantageous for maximizing the coverage of the flame shield according to the invention and thus maximizing its effectiveness.

[0085] The coverage of the flame shield is the ratio between the area of ​​the battery cover / battery tray side facing the battery that is covered by the flame shield and the total area of ​​the same side. This ratio is expressed as a percentage below.

[0086] Furthermore, in the battery housing according to the invention, the flame shielding element according to the invention can be applied integrally or in sections to the battery cover and / or battery tray, depending on design requirements.

[0087] Preferably, in order to enhance the flame shielding performance of the flame shielding component according to the invention, the coverage of the flame shielding component according to the invention is at least 50%, more preferably at least 60%, and even more preferably at least 70%.

[0088] Any range given in this specification should include the start and end points of the measurement, as well as the normal expected deviation. Different ranges of start and end points can be combined.

[0089] Other embodiments of the invention can be derived from this specification by combining different embodiments and examples of the invention, and also from the description of the embodiments shown in the accompanying drawings. The drawings are schematic and not necessarily drawn to scale.

[0090] In this disclosure, "battery electric vehicle" or "electric vehicle" means any vehicle that is powered even only partially by batteries, including but not limited to all-electric vehicles, hybrid vehicles, plug-in hybrid vehicles and vehicles equipped with range extenders.

[0091] A "layer" is an object composed of one or more materials that fills the space between two closely spaced surfaces, where the distance between the surfaces is substantially smaller than their dimensions. These two surfaces are referred to as the "sides" of the layer, and they are opposite each other. The distance between the two surfaces is called the thickness of the layer, which can be variable. Layers may include other layers. An airtight layer is defined as one that, when tested according to ASTM E 2178 or E 283, has an air permeability equal to or less than 0.02 l / sm at a pressure differential of 75 Pa. 2 The layers.

[0092] A “fiber layer” is an ordered or randomly oriented network of fibers that are bound together by chemical, mechanical, thermal, or solvent treatments. Attached Figure Description

[0093] Figure 1 The refractory layer according to the present invention is shown.

[0094] Figure 2 A battery case according to the present invention is shown.

[0095] Figure 3 A comparison of two samples and a reference sample according to the present invention is shown in a flame test. Detailed Implementation

[0096] Figure 1 A flame shield (1) formed from a refractory layer according to the invention is shown. In its simplest embodiment, the flame shield (1) comprises a substantially flat refractory layer consisting of reinforcing fibers (3) fully embedded in a PIR-based matrix material (2). As can be seen from the figure, polyisocyanurate completely surrounds the reinforcing fibers and blocks their pores, making the refractory layer impermeable to airflow. Preferably, there are no fiber ends protruding, at least on the surface facing a potential ignition source.

[0097] Figure 2A battery housing (30) for an electric vehicle according to the invention is shown, and the battery contained therein. The battery housing includes a battery cover (or battery top cover) (31) and a battery tray (32). The battery consists of a plurality of battery cells (33). A flame shield (1) according to the invention is applied to the side of the battery cover facing the battery, and it covers almost the entire extent of that side, even in areas with strong curvature and areas with ribs. The possibility of such good and safe coverage is a result of the excellent design flexibility of the two basic components of the flame shield according to the invention. Such good and safe coverage is difficult, if not impossible, for prior art mica-based flame shields because they are prone to cracking and / or breaking.

[0098] exist Figure 2 In the illustrated embodiment, the flame shield (1) according to the invention covers only the battery cover (31). In other embodiments not shown herein, the flame shield according to the invention may be applied only to the battery tray (32), or applied to both the battery cover (31) and the battery tray (32).

[0099] In the comparison, the two refractory layers according to the present invention and a reference sample were subjected to the refractory tests as described above.

[0100] Sample R is a reference sample containing a mica layer consisting of 90% mica and 10% silicone binder. Its thickness is 0.8 mm.

[0101] Sample A is the first sample according to the present invention, which contains 60% glass fiber embedded in PIR matrix material and has a thickness of about 1 mm.

[0102] Sample B is a second sample according to the present invention, which contains 60% glass fiber embedded in PIR matrix material and has a thickness of about 2 mm.

[0103] Surprisingly, the sample according to the invention performed just as well as the mica sample, showing no pores after being exposed to an open flame for 10 minutes. Even more surprisingly, the temperature measured on the surface facing away from the flame was the highest for mica at 499°C, while the temperatures of the two samples according to the invention were lower (sample A at 493°C and the 2mm sample at 395°C).

Claims

1. A flame shield for battery-electric vehicles, comprising at least one refractory layer, said refractory layer comprising reinforcing fibers with a melt temperature higher than 500°C fully embedded in a thermosetting matrix material, characterized in that... The matrix material includes at least one of polyisocyanurate or polyisocyanurate-polyurethane.

2. The flame shielding component according to claim 1, wherein the density of the refractory layer is 1000 kg / m³. 3 Up to 2400 kg / m 3 Optimal 1200kg / m 3 Up to 1800 kg / m 3 .

3. The flame shielding member according to any one of the preceding claims, wherein the weight of the reinforcing fiber is 20% to 95% of the total weight of the refractory layer, preferably 40% to 85% of the total weight of the refractory layer, and more preferably 50% to 70% of the total weight of the refractory layer.

4. The flame shielding member according to any one of the preceding claims, wherein the thickness of the at least one fire-resistant layer is at least 0.25 mm, preferably at least 0.25 to 10 mm, more preferably 0.25 to 4 mm, and even more preferably 1 to 3 mm.

5. The flame shield according to any one of the preceding claims, wherein the reinforcing fiber comprises at least one of the following: ceramic fiber, glass fiber, carbon fiber, mineral-based fiber, and oxidized polyacrylonitrile fiber.

6. The flame shield according to any one of the preceding claims, wherein, according to ISO 178, the flame shield has a bending strain of more than 1%, preferably more than 2%, at bending strength.

7. The flame shield according to any one of the preceding claims, wherein, according to ISO 178, the flexural modulus of the flame shield is greater than 5000 MPa, preferably greater than 7000 MPa.

8. The flame shielding member according to any one of the preceding claims, wherein the fire-resistant layer further comprises a flame retardant, preferably at least one of the following: chlorinated organic compounds and polymers, brominated organic compounds and polymers, phosphate-functionalized organic compounds and polymers, such as phosphate esters, chloroalkyl phosphate esters, phosphonates, and ammonium salts of phosphoric acid, polyphosphates, sulfuric acid, and hydrochloric acid, and / or flame retardant synergists, such as antimony trioxide, and / or inorganic compounds, such as calcium borate, zinc borate, zinc stannate, and zinc hydroxystannate.

9. The flame shield according to any one of the preceding claims, wherein the flame shield is capable of withstanding a fire resistance test at 1100°C for at least 10 minutes without forming holes or burn-through holes in the flame shield.

10. The flame shielding member according to any one of the preceding claims, wherein the reinforcing fiber comprises continuous filaments, or short fibers, or long fibers, or any combination of such fibers.

11. The flame shielding member according to any one of the preceding claims, wherein the reinforcing fibers are provided in the form of a nonwoven or textile structure, preferably a knitted fabric, needle-punched felt, or braid, tape, or a bonded nonwoven structure that maintains the structure in the final refractory layer.

12. The flame shield according to any one of the preceding claims, wherein the fire-resistant layer further comprises an adhesive to bond the reinforcing fibers prior to the embedding of the polyurethane matrix material, the adhesive preferably being a thermosetting adhesive, such as epoxy resin or polyurethane, or a ceramic thermosetting adhesive, such as silica or ceramic sol-gel.

13. The flame shielding member according to any one of the preceding claims, comprising two or more fire-resistant layers according to any one of the preceding claims.

14. A flame shield according to any one of the preceding claims, comprising at least one other layer, preferably at least one of the following: a metal layer, an aluminum layer, an expansion layer, a fiber layer comprising fibers with a melting temperature above 500°C, or melamine foam, wherein the at least one other layer is preferably on a surface facing away from a possible fire.

15. A housing for a battery-electric vehicle, comprising a battery cover and a battery tray, wherein the battery cover and / or the battery tray comprises at least one flame shielding element according to any one of claims 1 to 12.

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