Protective element

Abstract

The invention relates to a protective element (10), comprising at least one first layer (1) and at least one second layer (2), wherein the first layer (1) is made from elastomeric material and wherein the second layer (2) forms a flame-retardant layer (3).

Description

[0001] protective element

[0002] The invention relates to a protective element comprising at least a first layer and at least a second layer.

[0003] Such a protective element is known from DE 10 2018 113 815 A1. The previously known protective element is used in an energy storage system, wherein the energy storage system comprises a housing in which several storage cells are arranged.

[0004] Energy storage systems, especially rechargeable storage systems for electrical energy, are widely used, especially in mobile systems. Rechargeable storage systems for electrical energy are used, for example, in portable electronic devices such as smartphones or laptops. Furthermore, rechargeable storage systems for electrical energy are increasingly being used to provide energy for electrically powered vehicles. A wide range of electrically powered vehicles is conceivable, including passenger cars, two-wheelers, small vans, and trucks. Applications in robots, ships, aircraft, and mobile work machines are also conceivable. Other areas of application for electrical energy storage systems include stationary applications, for example in backup systems, in network stabilization systems, and for storing electrical energy from renewable energy sources.

[0005] A frequently used energy storage system is a rechargeable storage device in the form of a lithium-ion battery. Like other rechargeable electrical energy storage devices, lithium-ion batteries usually have several storage cells installed together in a single housing.

[0006] Several electrically connected storage cells are usually combined to form a module.

[0007] The energy storage system extends beyond lithium-ion batteries. Other rechargeable battery systems such as lithium-sulfur batteries, solid-state batteries, sodium-ion batteries, or metal-air batteries are also conceivable energy storage systems. Supercapacitors are also being considered as energy storage systems.

[0008] Energy storage systems in the form of rechargeable batteries exhibit their highest electrical capacity and best power input and output only within a limited temperature range. If the optimal operating temperature range is exceeded or undershot, the capacity, power input, and power output of the storage device drop significantly, and its functionality is impaired. Excessively high temperatures can also cause irreversible damage to the energy storage device. Therefore, both permanently elevated temperatures and short-term temperature peaks should be avoided at all costs. For lithium-ion batteries, for example, permanent temperatures of more than 50 °C and short-term temperature peaks of more than 80 °C should not be exceeded.

[0009] Particularly for applications in passenger cars, fast-charging capability of energy storage systems is required. The batteries forming an energy storage system should be fully or almost fully charged within a short time, for example within 15 minutes. Due to the charging system's efficiency of approximately 90% to 95%, large amounts of heat are released during the charging process in the energy storage system, which must be dissipated from the energy storage system. This heat is not released during normal operation. Therefore, the cooling system of the energy storage system must be designed to absorb the heat generated during the charging process. Excessively high temperatures can lead to irreversible damage to the energy storage system. In this context, the so-called thermal runaway is well known, particularly with lithium-ion cells.This releases large amounts of thermal energy as well as gaseous and particulate degradation products in a short time, resulting in high pressure and high temperatures in the housing. The pressure can be more than 10 bar and temperatures of up to 1,000 °C are possible. The particles can be very hot and abrasive. In prismatic cells, the release occurs particularly in the area of ​​the burst openings; in pouch cells, the location of the release is not defined. This effect is particularly problematic in energy storage systems with high energy density, such as that required to provide electrical energy in electric vehicles. Due to the increasing energy quantities of the individual cells and the increasing packing density of the cells arranged in the housing, the problem of thermal runaway is increasing. In addition to thermal runaway, there is also a risk of thermal propagation.Thermal propagation represents a cascade-like propagation of a thermal runaway preferentially to neighboring cells and - caused by hot particle streams and arcs - also to distant cells.

[0010] Likewise, flame penetration or at least a significant time delay of at least five minutes should be achieved. Firstly, the housing of the energy storage system should be protected to prevent the escape of hazardous particles. These could otherwise enter the passenger compartment of vehicles. Secondly, components adjacent to the housing of the energy storage system that require protection, such as other electronic components, should be protected. The protective element should prevent, or delay as long as possible, the particle stream emitted from the cell from damaging the component to be protected.

[0011] The invention is based on the object of providing a protective element that enables improved operational reliability. This object is achieved by the features of claim 1. The subclaims refer to advantageous embodiments.

[0012] The protective element according to the invention comprises at least a first layer and at least a second layer, wherein the first layer is made of elastomeric material and wherein the second layer forms a flame-retardant layer.

[0013] In this embodiment, the thermal conductivity of the first layer is limited by the material properties of the elastomeric material. The elastomeric material is designed such that it preferably has a maximum thermal conductivity coefficient of 3 W / (m K). Due to the limited thermal conductivity coefficient, heat transfer through the protective element is reduced, and the protective element exhibits thermal insulating properties.

[0014] The protective element according to the invention can shield the hot, possibly particle-laden and abrasive gas, liquid, and / or vapor streams from the housing wall in the event of a thermal runaway or thermal propagation. The housings and / or module walls arranged therein are often made of deep-drawn sheet steel, aluminum, thermoplastics, thermosetting plastics, or composite materials. In the event of damage, the protective element prevents the housing or module walls from being damaged to the extent that partial melting, cracking, or structural weakening occurs. Furthermore, the protective element prevents the uncontrolled and premature escape of flames, hot gas and particle streams, and thus also the uncontrolled ignition of the carrier and, in the case of electromobility, the ignition of the entire vehicle.

[0015] Furthermore, the elastomeric material is preferably partially or fully cross-linked. Cross-linking indicates how strongly the macromolecule chains of the elastomeric material are interconnected and form a network. Cross-linking can influence the elastic properties of the material. Preferably, cross-linking occurs in such a way that the elastomeric material is elastic. This makes it possible, on the one hand, for the protective element to have the desired, often even necessary, flexibility for assembly and to be installed in a targeted manner and, for example, bent. This simplifies assembly. Furthermore, with an elastic design, the protective element can absorb volume changes of adjacent components.

[0016] Furthermore, the elastomeric material is preferably designed such that the protective element has no, or at least a reduced, tendency to creep. This ensures that the protective element has a long service life and can be used even under long-term loads.

[0017] Peroxide vulcanization, platinum-catalyzed addition crosslinking, radiation crosslinking or room temperature vulcanization systems are particularly suitable as crosslinking systems.

[0018] An advantageous embodiment of the invention provides that the first layer comprises a silicone elastomer compound. A silicone elastomer compound has high thermal resistance. This ensures that the protective element is resistant to high temperatures. The silicone elastomer compound preferably comprises liquid silicone elastomer (LSR) or a high-temperature crosslinking silicone elastomer compound (HTV silicone elastomer compound). With such an embodiment, thermal degradation products, when exposed to flames, form a mineral film or protective layer that is thermally stable and electrically non-conductive and protects the remaining elastomer underneath with its protective properties. This further increases the operational reliability of the protective element. In addition, the protective element has a low tendency to chip.

[0019] The first layer may contain a first filler, wherein the first filler is made of organic material. Organic materials include, for example, materials such as polyimides, thermosets, polyacrylonitrile (PAN), oxidized PAN, aramids, cotton, or cellulose. These materials exhibit high-temperature stability and improve the resistance of the protective element to thermal stress.

[0020] The first layer can contain a second filler, wherein the second filler is made of inorganic material. Inorganic fillers of a first group include, for example, glass or ceramics, in particular basalt, aluminum oxide, mullite, or ZrO2. Inorganic fillers of a second group include, for example, oxides, hydroxides, or oxide hydroxides. Minerals such as mica, silicates, alkaline earth carbonates, or silicon dioxides are also conceivable. In principle, the second filler can be composed of a combination of the aforementioned materials.

[0021] The first filler and / or the second filler may contain fillers in the form of fibers. The elastomeric material forms an elastomer matrix, and the fibers are preferably bonded to the elastomer matrix by vulcanization.

[0022] This allows the advantageous properties of the fiber material to be combined with the advantageous properties of the elastomer matrix. The fibers preferably have a fiber length between 5 pm and 50 mm and a fiber diameter between 2 pm and 500 pm.

[0023] The first filler and / or the second filler can also additionally comprise further fibers whose fiber length and / or fiber diameter lie outside the specified ranges. Preferably, all fibers of the first filler and / or the second filler have a fiber length and / or a fiber diameter within the specified range. Preferably, the fibers are surrounded by the elastomer matrix to at least 90%, based on the sum of the surface areas of all fibers. The fibers preferably comprise organic material and / or inorganic material from the first group.

[0024] The first filler and / or the second filler can contain fillers in the form of particles. The elastomeric material forms an elastomer matrix. The particles are preferably surrounded by the elastomer matrix to at least 90%, based on the sum of the surfaces of all particles. The particles preferably have a spherical, platelet-shaped, or amorphous shape. Furthermore, the particles preferably have endothermic properties. The endothermic reaction can occur, for example, through a phase transition or through a chemical reaction. The desired temperature range for the endothermic reaction is between 100 and 800°C. This can further improve the temperature properties of the protective element. The particles preferably comprise inorganic material from the second group.

[0025] The first layer may contain an adhesion promoter. In this embodiment, silanes or resins are preferably used as adhesion promoters. This allows for improved bonding of the first and / or second filler to the elastomer matrix.

[0026] The flame-retardant layer can comprise a textile fabric. Woven and knitted fabrics are preferred textile fabrics, with the textile fabric comprising fibers. Fabrics made of randomly arranged fibers, such as felts or nonwovens, are also conceivable. Preferably, the textile fabric is surrounded by the elastomer matrix to at least 10% of the total surface area of ​​the textile fabrics.

[0027] The flame-retardant layer may comprise inorganic material. Examples of inorganic materials include glass or ceramic, particularly basalt, aluminum oxide, silicate, or ZrO2.

[0028] The flame-retardant layer can contain organic materials. Examples of organic materials include polyimides, thermosets, polyacrylonitrile (PAN), oxidized PAN, aramids, cotton, or cellulose. These materials exhibit high-temperature stability.

[0029] The flame-retardant layer may further comprise metallic material. Preferably, the flame-retardant layer comprises metal threads and / or metallic sheet structures. The protective element may have a surface structure. Preferably, the protective element has surface structures in the region of the exposed surfaces. The structure improves the deformability properties of the protective element and also has a thermal effect. Depending on the design of the macroscopic structure, channels may arise between the protective element and the adjacent component through which channels heat emitted by the adjacent component can be dissipated. It is also conceivable that the structure provides thermal insulation. Accordingly, it is conceivable to form fluid-conducting structures from the surface structure of the protective element.The fluid-conducting structures also make it possible to dissipate gases escaping from a storage cell in the event of a thermal runaway.

[0030] The protective element can be flat. Preferably, the flat protective element can be designed as a web. Furthermore, the protective element preferably has such elastic deformability that the protective element or the preform from which the protective element is made can be stored on a roll. This further increases the handling of the protective element. The protective element preferably has a thickness of 0.3 mm to 5 mm. The protective element particularly preferably has a thickness of 0.8 mm to 2.5 mm. This further increases the deformability of the protective element, so that the protective element has the desired elastic reaction upon expansion and contraction of adjacent components. Furthermore, the deformability of the protective element provides improved tolerance compensation.

[0031] The protective element can be designed as a molded part. In this configuration, the protective element can, in particular, form a flame-retardant seal.

[0032] The protective element is preferably equipped such that, upon thermal exposure, for example upon exposure to flames, it does not generate or release any electrically conductive particles on the side facing the flame. The invention further relates to an arrangement comprising a protective element, a flammable element, and an element to be protected from flames, wherein the protective element is arranged between the flammable element and the element to be protected from flames, wherein the flame-retardant layer of the protective element is arranged on the side facing away from the flammable element. Surprisingly, it has been found that particularly good flame protection is achieved when the first layer, made of elastomeric material, faces the flammable element, for example a cell burst opening.It has been found that this arrangement provides improved flame protection compared to an arrangement in which the second layer, forming the flame-retardant layer, faces the flammable element. One reason for this is that the elastomeric material of the first layer already exhibits excellent flame-retardant properties, while the high-temperature-resistant second layer forms a support layer even under high thermal loads and ensures mechanical stability. The element to be protected from flames can be a media-carrying or current-carrying device.

[0033] Furthermore, the arrangement according to the invention has the advantage that the flame-retardant layer made of fiber material can be placed between the first layer and the housing. Contamination from any released fibers can thus be avoided. Furthermore, contamination of the protective element is made more difficult by the outwardly smooth first layer.

[0034] In the described arrangement, the protective element protects the element to be protected, particularly against flames emanating from the flammable element. At the very least, the protective element provides a significant time delay. This greatly increases operational safety.

[0035] The invention further relates to an energy storage system comprising a protective element and a housing in which at least one storage cell is arranged, wherein the protective element is arranged between the at least one storage cell and the housing, wherein the flame-retardant layer is arranged on the side facing away from the storage cell. This corresponds to a specific embodiment of the previously described arrangement, wherein the storage cell is a flammable element and the housing is an element to be protected from flames. This arrangement can prevent or delay the escape of flames and / or gases from the housing, particularly in the event of thermal runaway or thermal propagation.

[0036] The protective element can be manufactured by calendering with continuous vulcanization. During calendering, the protective element is guided through the gaps of several rollers arranged one above the other. Flat protective elements are preferably produced this way. It is also conceivable to use injection molding to produce protective elements as molded parts. For special profile geometries of the protective elements, extrusion is also a possible manufacturing process. Depending on the manufacturing process, the surfaces of the protective elements can have embossing in the form of contours or ribs.

[0037] The protective element preferably exhibits a thickness increase of less than 50% upon exposure to heat, particularly upon exposure to flames. This distinguishes the protective element according to the invention from layers with an intumescent finish. The temperature protection mechanism of intumescent layers is based on creating a thermally insulating cushion consisting of thermal degradation products in situ in the event of thermal stress. In the present situation, however, this cushion would adversely impede the dissipation of gases released from the cell. This also increases the risk of blocking important components, such as a vent duct. This in turn can lead to a sharp increase in pressure in the energy storage system and to the bursting of the energy storage system. Furthermore, heat can build up in the blocked energy storage system, leading to a critically high temperature load on neighboring components.

[0038] The protective element can comprise at least a third layer. Preferably, the third layer is provided, which can be in the form of a coating that is applied to the protective element. In this embodiment, the third layer forms the outer layer of the protective element. The protective element can be equipped with the third layer on one side, multiple sides, or all sides. The third layer can be applied by spraying or doctoring. Preferably, the third layer comprises a polymeric material, for example, silicone elastomer or polyurethane. Furthermore, the third layer can contain intumescent and / or ceramizing materials that are embedded in the material of the third layer. The third layer further increases the protection of the protective element against thermal and / or mechanical stress.

[0039] Some embodiments of the protective element according to the invention are explained in more detail below with reference to the figures. These show, schematically:

[0040] Fig. 1 is a sectional view of a protective element;

[0041] Fig. 2 is a sectional view of an arrangement of the protective element;

[0042] Fig. 3 is a sectional view of a coated protective element.

[0043] Figure 1 shows a sectional view of a protective element 10. The protective element 10 comprises a first layer 1 and a second layer 2, wherein the first layer 1 is made of elastomeric material and wherein the second layer 2 forms a flame-retardant layer 3.

[0044] In the present embodiment, the elastomeric material of the first layer 1 has a thermal conductivity coefficient of 1.5 W / (m K). Furthermore, the elastomeric material in this embodiment is partially cross-linked to achieve good assembly properties through elastic properties. The elastomeric material is also elastic to accommodate volume changes of adjacent components. Furthermore, the elastomeric material has a reduced tendency to creep, making the protective element 10 suitable for long-term loads.

[0045] According to the present embodiment, the first layer 1 is made of silicone elastomer. Silicone elastomer exhibits high thermal resistance. In the present embodiment, the first layer 1 comprises a first filler, here oxidized polyacrylonitrile. In alternative embodiments, other organic fillers such as thermoset, polyacrylonitrile, polyimide, aramid, cotton, or cellulose can also be used.

[0046] In this embodiment, the first filler comprises fibers. The elastomeric material serves as the elastomer matrix, and the fibers are bonded to the elastomer matrix by vulcanization. The fibers are present as a fiber mixture with fiber lengths between 2 μm and 50 mm and fiber diameters between 2 μm and 400 μm. The fibers are largely embedded in the matrix and 95% surrounded by the elastomer matrix.

[0047] The first layer 1 comprises a second filler, in this case mica. In alternative embodiments, other inorganic fillers such as ceramics (in particular basalt, aluminum oxide, mullite, phlogopite, muscovite, or ZrC), glass, or inorganic oxides, hydroxides, or oxide hydroxides, but also minerals, silicates, alkaline earth carbonates, borates, or silicon dioxides can be used.

[0048] The second filler is in the form of particles. The particles are usually embedded in the matrix of the elastomer material and are at least 95% surrounded by the elastomer matrix. The particles have a spherical shape. Furthermore, the particles exhibit endothermic properties, which further improve the temperature properties of the protective element 10.

[0049] In the present embodiment, the first layer 1 comprises an adhesion promoter which serves to improve the bonding of the first filler and the second filler to the elastomer matrix.

[0050] The flame-retardant layer 3 comprises a textile fabric, which in this case is designed as a woven fabric. The textile fabric is only partially embedded in the matrix of the elastomer material and is only 20% surrounded by the elastomer matrix. In the present embodiment, the flame-retardant layer 3 comprises organic material, here oxidized polyacrylonitrile. In alternative embodiments, thermoset, polyacrylonitrile (PAN), polyimide, aramid, cotton, or cellulose, as well as inorganic material such as ceramic (in particular basalt, aluminum oxide, mullite, phlogopite, muscovite, or ZrCh) or glass, can also be used. Metallic materials are also conceivable in alternative embodiments, so that the flame-retardant layer 3 can comprise metal threads and / or metallic fabrics.

[0051] In the present embodiment, the protective element 10 has a surface structure in the area of ​​the exposed surfaces. This structure improves the deformability properties of the protective element 10 and also has a thermal effect. Furthermore, it enables easy attachment of the protective element 10 to a housing, for example, using an adhesive.

[0052] In the present embodiment, the protective element 10 is flat and is provided as a web. In alternative embodiments, the protective element 10 can also be formed as a molded part. Due to the elastic deformability of the protective element 10, the protective element 10 can be stored, in particular, on a roll. In the present embodiment, the protective element 10 has a thickness of 1.5 mm.

[0053] The protective element 10 is produced by calendering with continuous vulcanization. Alternatively, the protective element 10 is produced by extrusion with continuous vulcanization.

[0054] In the present embodiment, the protective element 10 has a thickness increase of at most 25% when exposed to flame.

[0055] Figure 2 shows an arrangement 20 of the protective element 10 shown in Figure 1. In addition to the protective element 10, the arrangement 20 comprises a flammable element 4 and an element 5 to be protected from flames. The protective element 10 is arranged between the flammable element 4 and the element 5 to be protected from flames. The flame-retardant layer 3 of the protective element 10 is arranged on the side facing away from the flammable element 4. The flame-retardant layer 3 of the protective element 10 is therefore arranged on the side facing the element 5 to be protected from flames. In this arrangement 20, the protective element 10 protects the element 5 to be protected, in particular, from the penetration of flames emanating from the flammable element 4.

[0056] At least the protective element 10 ensures a significant time delay.

[0057] The arrangement 20 shown in Figure 2 forms an energy storage system equipped with one or more protective elements 10. The flammable element 4 is an energy storage cell, and the element 5 to be protected from flames 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 facing away from the storage cell. Furthermore, the protective element 10 can protect other components of the energy storage system, for example, control units, current-carrying lines, or coolant pipes, and the like.

[0058] In the event of damage, the protective element 10 prevents excessive heat stress on the element 5 to be protected from flames, i.e., the housing. The protective element 10 is designed so that it exhibits a maximum thickness increase of 50% upon exposure to heat, particularly flame exposure. This avoids the problem of the protective element 10 blocking the blow-off duct in the event of damage.

[0059] Figure 3 shows the protective element 10 shown in Figure 1 with a third layer 6.

[0060] In the present embodiment, the third layer 6 comprises a matrix, wherein the matrix comprises polyurethane. According to a further embodiment, the matrix comprises silicone. Furthermore, the third layer 6 comprises intumescent and ceramizing materials embedded in the matrix. The third layer further increases the protection of the protective element 10 against thermal and mechanical stress. In the present embodiment, the third layer 6 is applied to both sides of the protective element 10 as a coating of the protective element 10.

Claims

Patent claims 1 . Protective element (10) comprising at least a first layer (1) and at least a second layer (2), wherein the first layer (1) is made of elastomeric material and wherein the second layer (2) forms a flame-retardant layer (3).

2. Protective element according to claim 1, characterized in that the first layer (1) comprises silicone elastomer.

3. Protective element according to one of claims 1 or 2, characterized in that the first layer (1) comprises a first filler, wherein the first filler is formed from inorganic material.

4. Protective element according to one of claims 1 to 3, characterized in that the first layer (1) comprises a second filler, wherein the second filler is formed from organic material.

5. Protective element according to one of claims 1 to 4, characterized in that the first filler and / or the second filler contains fillers in fiber form.

6. Protective element according to one of claims 1 to 5, characterized in that the first filler and / or the second filler contains fillers in particle form.

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

8. Protective element according to one of claims 1 to 7, characterized in that the flame-retardant layer (3) comprises a textile fabric.

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

10. Protective element according to one of claims 1 to 8, characterized in that the flame-retardant layer (3) comprises organic material. 11 . Protective element according to one of claims 1 to 10, characterized in that the flame-retardant layer (3) comprises metallic material.

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

13. Protective element according to one of claims 1 to 12, characterized in that the protective element (10) is flat.

14. Protective element according to one of claims 1 to 13, characterized in that the protective element (10) is designed as a molded part.

15. Protective element according to one of claims 1 to 14, characterized in that the increase in thickness of the protective element (10) under thermal influence is less than 50%.

16. Arrangement (20) comprising a protective element (1) according to one of the preceding claims, a flammable element (4) and an element to be protected from flames (5), wherein the protective element (1) is arranged between the flammable element (4) and the element to be protected from flames (5), wherein the flame protection layer (3) of the protective element (1) is arranged on the side facing away from the flammable element (4).

17. Arrangement according to claim 16, characterized in that the element (5) to be protected from flames is a media-carrying or a current-carrying device.

18. Energy storage system, comprising a protective element (1) according to 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, wherein the flame retardant layer (3) is arranged on the side facing away from the storage cell.

19. The energy storage system according to claim 18, further comprising a flammable element (4) and an element to be protected from flames (5), wherein the protective element (1) is arranged between the flammable element (4) and the element to be protected from flames (5), wherein the flame-retardant layer (3) of the protective element (1) is arranged on the side facing away from the flammable element (4).

20. The energy storage system according to claim 19, characterized in that the element to be protected from flames (5) is a media-conducting or a current-conducting device.

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