Protection elements

Abstract

A protective element (10) comprising at least one first layer (1) and at least one second layer (2), the first layer (1) being made of an elastomeric material and the second layer (2) forming a flame-retardant layer (3).

Description

[Technical Field]

[0001] The present invention relates to a protective element, comprising at least one first layer and at least one second layer. [Background technology]

[0002] Such a protective element is known from DE 10 2018 113 815 A1. The known protective element is used in an energy storage system, which comprises a housing in which a number of storage cells are arranged.

[0003] Energy storage systems, especially rechargeable accumulators for electrical energy, are widespread, especially in mobile systems. Rechargeable accumulators for electrical energy are used, for example, in portable electronic devices, such as smartphones or laptops. Furthermore, rechargeable accumulators for electrical energy are often used to provide energy to electrically driven vehicles. In this case, many types of electrically driven vehicles are possible, including not only passenger cars but also motorcycles, vans, or trucks. Applications in robots, ships, aircraft, and mobile work machines are also possible. Further areas of use for electrical energy storage systems are, for example, stationary applications in backup systems, stationary applications in network stability systems, and stationary applications for storing electrical energy from renewable energy sources.

[0004] In this case, the energy storage system often used is a rechargeable accumulator in the form of a lithium-ion accumulator, which, like other rechargeable accumulators for electrical energy, usually has several storage cells assembled together in a housing, where the storage cells are electrically connected to one another and are often grouped together in a module.

[0005] In this case, the energy storage system does not only include lithium-ion accumulators. Other rechargeable battery systems, such as lithium-sulfur batteries, solid-state batteries, sodium-ion batteries or metal-air batteries, are also possible energy storage systems. Furthermore, supercapacitors are also considered as energy storage systems.

[0006] Energy storage systems in the form of rechargeable batteries have maximum electrical capacity and optimal power input and output only within a limited temperature range. Above or below the optimal operating temperature range, the battery's capacity, power input, and power output capabilities are significantly reduced, impairing the functionality of the energy storage device. Furthermore, excessively high temperatures can irreversibly damage the energy storage device. Therefore, not only sustained elevated temperatures but also short-term temperature peaks must be avoided. In the case of lithium-ion batteries, for example, sustained temperatures above 50°C and short-term temperature peaks above 80°C must not be exceeded.

[0007] Especially in passenger vehicle applications, rapid charging performance is required for energy storage systems. In this case, the storage battery forming the energy storage system must be fully or nearly fully charged within a short time, for example, within 15 minutes. Due to the charging system efficiency of approximately 90% to 95%, a large amount of heat is released during the charging process in the energy storage system, which must be dissipated from the energy storage system. This heat is not released under normal operating conditions. Therefore, it is necessary to design a cooling system for the energy storage system that can absorb the heat generated during the charging process.

[0008] Excessively high temperatures can lead to irreversible damage to the energy storage system. In this context, so-called thermal runaway is known, particularly in lithium-ion cells. In this case, a high amount of thermal energy and gaseous and particulate decomposition products are released within a short period of time, resulting in high pressures and temperatures within the housing. Pressures can exceed 10 bar and temperatures can reach up to 1,000 °C. The particles are highly abrasive. In the case of prismatic cells, the release occurs primarily in the area of the rupture opening, while in pouch-type cells, the release point is undefined. This phenomenon is particularly problematic in energy storage systems with high energy densities, such as those required to provide electric energy to electric vehicles. The problem of thermal runaway increases with the increasing energy content of individual cells and the increasing packing density of the cells arranged in the housing. In addition to thermal runaway, there is also the risk of heat propagation. Heat propagation causes thermal runaway to propagate preferentially to adjacent cells and - due to hot particle flow and arcing - to distant cells in a cascading manner.

[0009] Additionally, a significant time delay of at least five minutes or less must be achieved to prevent flame propagation. First, the energy storage system housing must be protected to prevent dangerous particles from escaping, which would otherwise reach the passenger compartment of the vehicle. Second, components that must be protected adjacent to the energy storage system housing, such as other electronic components, must be protected. The protective elements must prevent or, as far as possible, delay the particle flow emitted by the cell from damaging the protected components. Summary of the Invention [Problem to be solved by the invention]

[0010] The problem underlying the present invention is to provide a protective element which allows for improved operational safety. [Means for solving the problem]

[0011] This problem is solved by the features of claim 1. Advantageous configurations are set forth in the dependent claims.

[0012] The protective element according to the invention comprises at least one first layer and at least one second layer, the first layer being made from an elastomeric material and the second layer forming a flame-retardant layer.

[0013] In this configuration, the thermal conductivity of the first layer is limited by the material properties of the elastomeric material, which is preferably configured to have a thermal conductivity of up to 3 W / (m·K). The limited thermal conductivity reduces heat transport through the protective element, giving the protective element insulating properties.

[0014] The protective element of the present invention can shield the housing wall from hot, possibly particle-laden, abrasive gas, liquid, and / or vapor flows during thermal runaway and heat propagation that have already occurred. The housing and / or the module walls arranged within the housing are often made of deep-drawn steel, aluminum, thermoplastic plastics, thermosetting plastics, or composite materials. The protective element prevents the housing or module wall from sustaining damage that could lead to partial melting, crack formation, or structural weakening in the event of an attack. Furthermore, the protective element prevents fires, premature release of hot gas particle flows, and thus uncontrolled ignition of the support structure and, in the case of electromobility, fires of the entire vehicle.

[0015] Furthermore, the elastomeric material is preferably partially or fully crosslinked. Crosslinking here refers to how strongly the macromolecular chains of the elastomeric material are crosslinked with one another to form a network structure. Crosslinking can influence the elastic properties of the material. Preferably, the crosslinking is carried out so that the elastomeric material is elastically formed. This allows, for example, for the protective element to have the desired flexibility, which is often required for assembly, and to be assembled and, for example, bent properly. This simplifies assembly. Furthermore, the protective element, when elastically configured, can absorb volume changes of adjacent components.

[0016] Furthermore, the elastomeric material is preferably designed so that the protective element does not tend to creep, or at least has a reduced tendency to creep, which increases the useful life of the protective element and allows it to be used under prolonged loads.

[0017] As crosslinking systems, in particular peroxide vulcanization, platinum-catalyzed addition crosslinking, light crosslinking or room temperature vulcanization systems come into consideration.

[0018] An advantageous embodiment of the present invention specifies that the first layer comprises a silicone elastomer compound. Silicone elastomer compounds have high heat resistance, thereby providing the protective element with resistance to high temperatures. Preferably, the silicone elastomer compound comprises a liquid silicone elastomer (LSR) or a high-temperature crosslinkable silicone elastomer compound (HTV silicone elastomer compound). In this embodiment, the pyrolysis products form, upon contact with flame, an inorganic film or protective layer that is thermally stable and non-conductive and protects the remaining elastomer on the backside with its protective properties. This further improves the operational safety of the protective element. Furthermore, this reduces the protective element's tendency to rupture.

[0019] The first layer includes a first filler, which may be made of an organic material, such as polyimide, thermosetting resin, polyacrylonitrile (PAN), oxidized PAN, aramid, cotton, or cellulose, which have high-temperature stability properties and improve the resistance of the protective element to temperature loads.

[0020] The first layer includes a second filler, which may be made of an inorganic material. The first group of inorganic fillers may be, for example, glass or ceramics, particularly basalt, aluminum oxide, mullite, or ZrO2. The second group of inorganic fillers may be, for example, oxides, hydroxides, or oxide hydroxides. Minerals such as mica, silicates, alkaline earth carbonates, or silicon dioxide are also possible. In principle, the second filler may be made of a combination of the aforementioned materials.

[0021] The first filler and / or the second filler may contain fillers in the form of fibers. In this case, the elastomeric material forms an elastomeric matrix, and the fibers are bonded to the elastomeric matrix, preferably by vulcanization. This allows the advantageous properties of the fibrous material to be combined with those of the elastomeric matrix. Preferably, the fibers have a fiber length of 5 μm to 50 mm and a fiber diameter of 2 μm to 500 μm.

[0022] In this case, the first filler and / or the second filler may additionally contain other fibers whose fiber length and / or fiber diameter are outside the above range. Preferably, all of the fibers of the first filler and / or the second filler have fiber length and / or fiber diameter within the above range. Preferably, at least 90% of the fibers, based on the total surface area of all the fibers, are surrounded by the elastomeric matrix. The fibers preferably comprise organic materials and / or inorganic materials of the first group.

[0023] The first filler and / or the second filler may contain fillers in the form of particles. In this case, the elastomeric material forms an elastomeric matrix. Preferably, at least 90% of the particles, based on the total surface area of all particles, are surrounded by the elastomeric matrix. Preferably, the particles have a spherical, plate-like, or amorphous shape. Furthermore, the particles preferably have endothermic properties. The endothermic properties can be achieved, for example, by phase transition or chemical transformation. The desired temperature range for endothermic properties is 100 to 800°C. This can further improve the thermal properties of the protective element. The particles preferably comprise inorganic materials of the second group.

[0024] The first layer may contain an adhesion promoter, preferably a silane or a resin, which can improve the bonding of the first and / or second filler to the elastomeric matrix.

[0025] The flame-retardant layer may include a fiber sheet. Woven fabrics and knitted fabrics are preferred fiber sheets, in which case the fiber sheet contains fibers. Also possible are sheets of stochastically arranged fibers, such as felt or nonwoven fabrics. Preferably, at least 10% of the fiber sheet, based on the total surface area of the fiber sheet, is surrounded by an elastomeric matrix.

[0026] The flame-retardant layer may comprise an inorganic material, such as glass or ceramic, in particular basalt, aluminum oxide, silicates or ZrO2.

[0027] The flame-retardant layer may include an organic material, such as polyimide, thermosetting resin, polyacrylonitrile (PAN), oxidized PAN, aramid, cotton, or cellulose, which has high-temperature stability properties.

[0028] The flame-retardant layer may further include a metal material, and preferably includes metal threads and / or metal sheet structures.

[0029] The protective element may have a surface patterning. Preferably, the protective element has a surface patterning in the free surface area. This patterning improves the deformation characteristics of the protective element, and also has a thermal effect. Depending on the macroscopic configuration of the patterning, a path can be created between the protective element and an adjacent component, through which heat dissipated from the adjacent component can be dissipated. The patterning can also provide thermal insulation. Accordingly, the surface patterning of the protective element can be used to create a fluid guide pattern. This fluid guide pattern can also be used to guide gases escaping from the storage cell in the event of thermal runaway.

[0030] The protective element may be formed in a planar shape. Preferably, the planar protective element may be formed as a web article. Furthermore, the protective element preferably has a certain degree of elastic deformability, which allows the protective element or the preform from which the protective element is produced to be stored in a roll. This further improves the handleability of the protective element. The protective element preferably has a thickness of 0.3 mm to 5 mm. The protective element is particularly preferably 0.8 mm to 2.5 mm. This further improves the deformability of the protective element, so that the protective element exhibits the desired elastic response during expansion and contraction of adjacent components. Furthermore, the protective element has improved tolerance compensation due to its deformability.

[0031] The protective element can be configured as a molded part, in which case the protective element can in particular form a flame-retardant seal.

[0032] The protective element is preferably equipped in such a way that when exposed to heat, in particular when exposed to flame, it does not generate or emit electrically conductive particles on the side of this flame.

[0033] The present invention also relates to an assembly comprising a protective element, a flammable element, and an element to be protected against flame, i.e., a flame-retardant element, where the protective element is disposed between the flammable element and the flammable element, and the flame-retardant layer of the protective element is disposed on the side opposite the flammable element. Surprisingly, it has been found that particularly good flame retardancy can be achieved when a first layer formed from an elastomeric material is oriented toward the flammable element, e.g., toward the cell rupture opening. This assembly exhibits improved flame retardancy compared to assemblies in which a second layer forming the flame-retardant layer is oriented toward the flammable element. This is because the elastomeric material of the first layer already has excellent flame-retardant properties, and in this case, the heat-resistant second layer forms a support layer and provides mechanical stability, even under high thermal loads. The flame-retardant element may be a device for guiding media or conducting electricity.

[0034] Furthermore, the assembly according to the invention has the advantage that a flame-retardant layer made of a fiber material can be arranged between the first layer and the housing, thus preventing possible contamination by released fibers. Furthermore, the outwardly smooth first layer makes it difficult for the protective element to be contaminated.

[0035] In the above-described assembly, the protective element protects the element to be protected, in particular against the propagation of a flame originating from a combustible element, or at least provides a significant time delay, which significantly increases operational safety.

[0036] The present invention also relates to an energy storage system comprising a protective element and a housing with at least one storage cell disposed therein, the protective element being disposed between the at least one storage cell and the housing, and a flame-retardant layer being disposed on the opposite side of the storage cell. This corresponds to a specific configuration of the above-described assembly, in which the storage cell is the combustible element and the housing is the flame-retardant element. This assembly can prevent or delay the escape of flame and / or gases from the housing, especially in the event of thermal runaway or heat propagation.

[0037] The protective element can be produced by a calendering process with continuous vulcanization. During this calendering process, the protective element is guided through the gap between several rolls arranged one above the other. Preferably, a planar protective element is produced in this way. It is also possible to use an injection molding method to produce the protective element as a molded part. For special cross-sectional geometries of the protective element, extrusion is also a possible production process. Depending on the production process, the surface of the protective element can have embossments in the form of contours or ribs.

[0038] Preferably, the protective element increases in thickness by less than 50% upon thermal action, especially upon exposure to flame. This distinguishes the protective element according to the present invention from layers equipped with intumescent devices. The thermal protection mechanism of the intumescent layer is based on the provision of an insulating cushion of pyrolysis products in situ during thermal loads. However, in these situations, this cushion undesirably impedes the escape of gases released from the cells. This further increases the risk of blocking critical components, such as the outlet pipes. This can, on the one hand, lead to a significant pressure increase in the energy storage system and its rupture. On the other hand, heat generation can occur in the blocked energy storage system, leading to critically high temperature loads on adjacent components.

[0039] The protective element may include at least one third layer. Preferably, the third layer may be in the form of a coating applied to the protective element. In this configuration, the third layer forms the outer layer of the protective element. The protective element may be provided with the third layer on one, several, or all sides. The third layer may be applied by spray coating or doctor coating. Preferably, the third layer comprises a polymer material, such as a silicone elastomer or polyurethane. Furthermore, the third layer may contain an expandable and / or ceramizing material embedded in the material of the third layer. The third layer further improves the protection of the protective element against thermal and / or mechanical loads.

[0040] In the following, some configurations of the protective element according to the invention will be explained in more detail with reference to the drawings. [Brief explanation of the drawings]

[0041] [Figure 1] 1 is a schematic cross-sectional view of a protective element. [Figure 2] 1 is a schematic cross-sectional view of an assembly of protective elements. [Figure 3] 1 is a schematic cross-sectional view of a coated protective element. DETAILED DESCRIPTION OF THE INVENTION

[0042] 1 shows a cross-section of a protective element 10. The protective element 10 comprises a first layer 1 made of an elastomeric material and a second layer 2 forming a flame-retardant layer 3.

[0043] The elastomer material of the first layer 1 has a thermal conductivity of 1.5 W / (m·K) in the illustrated configuration. Furthermore, the elastomer material is partially crosslinked in this configuration, which provides good assembly characteristics due to its elastic properties. The elastomer material is also elastically configured to absorb volume changes of adjacent components. Furthermore, the elastomer material has a reduced tendency to creep, which makes the protective element 10 suitable for long-term loading.

[0044] In the illustrated configuration, the first layer 1 is made of a silicone elastomer, which has high heat resistance.

[0045] The first layer 1 includes a first filler material, in this configuration polyacrylonitrile oxide, in alternative configurations other organic fillers may be used, such as thermosetting resins, polyacrylonitrile, polyimide, aramid, cotton or cellulose.

[0046] The first filler, in the illustrated configuration, contains fibers. In this case, an elastomeric material acts as the elastomeric matrix, and the fibers are bonded to the elastomeric matrix by vulcanization. The fibers are present as a fiber mixture with fiber lengths ranging from 2 μm to 50 mm and fiber diameters ranging from 2 μm to 400 μm. The majority of the fibers are embedded within the matrix, with 95% surrounded by the elastomeric matrix.

[0047] The first layer 1 contains a second filler, in this configuration mica. In alternative configurations, other inorganic fillers may be used, such as ceramics (in particular basalt, aluminum oxide, mullite, phlogopite, muscovite or ZrO2), glass or inorganic oxides, hydroxides or oxide hydroxides, as well as minerals, silicates, alkaline earth carbonates, borates or silicon dioxide.

[0048] In this case, the second filler is present in the form of particles. The particles are often embedded in a matrix of elastomeric material, in which case they are at least 95% surrounded by the elastomeric matrix. The particles have a spherical shape. Furthermore, the particles have heat-absorbing properties, which further improve the temperature characteristics of the protective element 10.

[0049] The first layer 1, in the construction shown, includes an adhesion promoter which serves to improve the bonding of the first and second fillers to the elastomeric matrix.

[0050] The flame-retardant layer 3 in this configuration includes a fibrous sheet formed as a woven fabric, which is only partially embedded in a matrix of elastomeric material, with only 20% of the fibrous sheet being surrounded by the elastomeric matrix.

[0051] In the illustrated configuration, the flame-retardant layer 3 comprises an organic material, in this case polyacrylonitrile oxide. In alternative configurations, thermosetting resins, polyacrylonitrile (PAN), polyimide, aramid, cotton or cellulose, as well as inorganic materials such as ceramics (especially basalt, aluminum oxide, mullite, phlogopite, muscovite or ZrO2) or glass may be used. In alternative configurations, metallic materials are also possible, whereby the flame-retardant layer 3 may comprise metal threads and / or metallic sheet structures.

[0052] In the illustrated configuration, the protective element 10 has a surface patterning in the free surface area, which on the one hand improves the deformation properties of the protective element 10 and on the other hand also has a thermal effect, and furthermore allows for easy bonding of the protective element 10 to a housing, for example by adhesive.

[0053] In the illustrated configuration, the protective element 10 is formed as a sheet and is present as a web article. In an alternative configuration, the protective element 10 may be formed as a shaped piece. The elastic deformability of the protective element 10 allows it to be stored, in particular in a roll. In the illustrated configuration, the protective element 10 has a thickness of 1.5 mm.

[0054] The protective element 10 is manufactured by a calendaring process with continuous vulcanization. Alternatively, the protective element 10 is manufactured by an extrusion process with continuous vulcanization.

[0055] In the illustrated configuration, the protective element 10 experiences a maximum thickness increase of 25% upon contact with flame.

[0056] Figure 2 shows an assembly 20 of the protective element 10 shown in Figure 1. In addition to the protective element 10, this assembly 20 also comprises a combustible element 4 and a flame-retardant element 5. The protective element 10 is arranged between the combustible element 4 and the flame-retardant element 5. The flame-retardant layer 3 of the protective element 10 is arranged on the side opposite the combustible element 4, i.e., on the side of the flame-retardant element 5. In this assembly 20, the protective element 10 protects the element 5 to be protected, in particular against the propagation of a flame originating from the combustible element 4. At the very least, the protective element 10 provides a significant time delay.

[0057] The assembly 20 shown in Figure 2 forms an energy storage system equipped with one or more protective elements 10. In this case, the combustible element 4 is an energy storage cell and the flame-retardant element 5 is a housing. The protective element 10 is arranged between the storage cell and the housing, with the flame-retardant layer 3 being arranged on the side opposite the storage cell. Furthermore, the protective element 10 can protect other components of the energy storage system, such as control equipment, current-carrying lines or refrigerant lines, and the like.

[0058] The protective element 10 prevents excessive heat loads on the flame-protected element 5, i.e., the housing, in the event of damage. In this case, the protective element 10 is designed so that it increases in thickness by up to 50% when exposed to heat, especially when exposed to flame. This prevents the protective element 10 from blocking the air passages in the event of damage.

[0059] 3 shows the protective element 10 shown in FIG. 1 with a third layer 6. In the illustrated configuration, the third layer 6 comprises a matrix, which in this case comprises polyurethane. In another configuration, the matrix comprises silicone. Furthermore, the third layer 6 comprises an expandable and ceramifying material embedded in the matrix. The third layer further improves the protection of the protective element 10 against thermal and mechanical loads. In the illustrated configuration, the third layer 6 is applied to both sides of the protective element 10 as a coating on the protective element 10.

Claims

1. A protective element (10) comprising at least one first layer (1) and at least one second layer (2), said first layer (1) being made of an elastomeric material and said second layer (2) forming a flame-retardant layer (3).

2. 2. A protective element according to claim 1, characterized in that said first layer (1) comprises a silicone elastomer.

3. 3. A protective element according to claim 1 or 2, characterized in that the first layer (1) comprises a first filler, which is made of an inorganic material.

4. 4. A protective element according to any one of claims 1 to 3, characterized in that the first layer (1) comprises a second filler, which is made of an organic material.

5. 5. Protective element according to any one of claims 1 to 4, characterized in that the first filler material and / or the second filler material contain filler material in the form of fibers.

6. 6. Protective element according to claim 1, characterized in that the first filler and / or the second filler contains filler in particulate form.

7. 7. Protective element according to any one of claims 1 to 6, characterized in that the first layer (1) contains an adhesion promoter.

8. 8. A protective element according to any one of claims 1 to 7, characterized in that the flame-retardant layer (3) comprises a textile sheet structure.

9. 9. Protective element according to any one of claims 1 to 8, characterized in that the flame-retardant layer (3) comprises an inorganic material.

10. 9. Protective element according to any one of claims 1 to 8, characterized in that the flame-retardant layer (3) comprises an organic material.

11. 11. Protective element according to any one of claims 1 to 10, characterized in that the flame-retardant layer (3) comprises a metallic material.

12. 12. A protective element according to any one of claims 1 to 11, characterized in that the protective element (10) has a surface patterning.

13. 13. A protective element according to any one of claims 1 to 12, characterized in that the protective element (10) is formed in a surface-like manner.

14. 14. The protective element according to claim 1, wherein the protective element (10) is configured as a molded part.

15. 15. A protective element according to any one of claims 1 to 14, characterized in that the thickness of the protective element (10) increases by less than 50% when exposed to heat.

16. 16. An assembly (20) comprising a protective element (1) according to any one of claims 1 to 15, a flammable element (4), and a flame-retardant element (5), wherein the protective element (1) is arranged between the flammable element (4) and the flame-retardant element (5), and the flame-retardant layer (3) of the protective element (1) is arranged on the side opposite the flammable element (4).

17. Assembly according to claim 16, characterized in that the flame-proof element (5) is a device for media guidance or for carrying current.

18. 16. An energy storage system comprising a protective element (1) according to any one of claims 1 to 15 and a housing in which at least one storage cell is arranged, wherein the protective element (1) is arranged between the at least one storage cell and the housing, and the flame-retardant layer (3) is arranged on the side opposite the storage cell.

19. 19. The energy storage system of claim 18, further comprising a flammable element (4) and a flame-retardant element (5), wherein the protective element (1) is arranged between the flammable element (4) and the flame-retardant element (5), and the flame-retardant layer (3) of the protective element (1) is arranged on the side opposite the flammable element (4).

20. 20. Energy storage system according to claim 19, characterized in that the flame-proof element (5) is a device for media guidance or for carrying current.

Images