Fire protection shield for a battery cell

Abstract

The present invention relates to a fire protection shield (30) for a battery cell, wherein the fire protection shield (30) comprises an inner layer (31), an active layer (32), and an outer layer (33). The active layer (32) comprises a first means (40), in particular a fire extinguishing agent, and a second means (50), wherein the first and the second means exhibit different fire protection effects upon activation.

Description

[0001] The invention relates to a fire protection shield for a battery cell.

[0002] Battery cells or accumulator cells used for high-performance operation of electrical machines, such as those in electric vehicles, are often made of lithium-ion batteries. Such batteries have a safe operating range, outside of which self-destructive mechanisms can occur within the battery.

[0003] One such mechanism is so-called "thermal runaway," or the thermal runaway of battery cells. This is characterized by an extreme and sudden temperature increase within the battery cell, triggered by a series of exothermic chain reactions. This extreme temperature increase can also lead to the ignition of neighboring battery cells.

[0004] During thermal runaway, gases are released from the battery, among other things, which can lead to a highly flammable chain reaction within the battery cell. This can cause fires with temperatures of up to 1200°C.

[0005] Furthermore, oxidation processes, i.e. the reaction of lithium with the oxygen produced in the battery cell, such as those that can occur when charging at low temperatures or when charging with a high charging current, can cause dendrites to form in the battery cells, which cause the battery cell to swell and, in extreme cases, can “burst” the battery (cell) from the inside out.

[0006] Previous methods for preventing thermal runaway in battery cells typically involve applying a fire-resistant protective layer over the battery cell. Furthermore, materials designed to capture, divert, and / or bind the resulting gases are used.

[0007] Patent application EP 3 352 286 A1 describes a laminated layer for absorbing the gases generated in a battery. A layer of gas-adsorbing, azo-bonded polymer is applied to a heat-resistant or heat-repellent layer and laminated to an outer jacket layer.

[0008] In the published patent application EP 3 327 854 A1, a gas-adsorbing material is applied directly to the electrode connector of a battery cell.

[0009] The published patent application US 2010 / 0255359 A1 describes a battery assembly comprising a heat-absorbing material, wherein the heat-absorbing material can absorb a temperature of 300 °C caused by gases escaping from a battery cell of the battery assembly. Various materials are mentioned as heat-absorbing materials, e.g., metal, ceramic, sand, liquids, and gases.

[0010] A protective barrier for a battery cell or a battery module is also known from published patent application US 2016 / 0218336 A1. The protective barrier consists of a thermally resistant material and has a venting channel extending from a vent valve of the battery cell to a vent cell to a vent valve of a housing in which the battery cell is arranged.

[0011] The Taiwanese patent TWI670887 B describes a protective structure for limiting thermal runaway of a battery cell. If the temperature of the battery cell reaches a critical temperature, an extinguishing agent can escape from a chamber that ruptures due to the high temperature into the battery cell, thus preventing the battery cell from burning out.

[0012] Published patent application EP 4 057 370 A2 proposes a battery assembly comprising a housing and at least one battery cell arranged therein, as well as a barrier element arranged between the battery cell and the housing. The barrier element has a multilayer structure with at least two material layers—a porous polymer matrix or a porous plastic and a gas-permeable and high-temperature-resistant material, e.g., a ceramic material.

[0013] Published application WO 2020 / 047846 A1 is directed to a fire protection element for preventing thermal runaway in batteries, comprising a flame barrier layer and a passive thermal insulation layer. The fire protection element can consist of several layers of porous polymer.

[0014] An insulating element for a battery is known from published patent application US 2006 / 068 278 A1. This element can consist of several layers, e.g., a binder and fiber materials. Alternatively, a polymer foam is also proposed.

[0015] Published application WO 2019 / 121641 A1 discloses a multilayer thermal insulation element used in batteries to protect against thermal runaway. Fiber layers and metal layers (including porous metal layers) as well as adhesive layers (binders) are proposed.

[0016] The known devices essentially aim to prevent a fire in a battery cell, but most methods are limited to the introduction of a functional layer to capture gases generated in the battery cell and the additional use of a fire-resistant material for shielding.

[0017] None of the devices available to date are capable of not only specifically absorbing battery gases but also of “extinguishing” a fire that has started in a battery cell, thus preventing it from spreading to other battery cells.

[0018] The object of the present invention is to provide a fire protection device which at least partially overcomes the above-mentioned disadvantages.

[0019] This object is achieved by the fire protection screen according to the invention according to claim 1.

[0020] Further advantageous embodiments of the invention emerge from the subclaims and the following description of preferred embodiments of the present invention.

[0021] A fire protection shield according to the invention for a battery cell comprises - an inner layer, - an active layer, and - an outer layer, wherein the active layer comprises a first agent, in particular an extinguishing agent, and a second agent, wherein the first and second agents exert different fire protection effects when activated.

[0022] A fire protection shield according to the invention can be designed such that it encloses each battery cell, and thus simultaneously each battery module and thus the entire vehicle battery, for example on three sides. A battery cell is a basic cell, with several basic cells forming a battery module and several modules in turn forming a vehicle battery. For example, battery modules consisting of 12-20 individual batteries (corresponding to an entire battery system used in electric vehicles) can be equipped with the present fire protection shield. The present fire protection shield can be used for any individual battery type, for example a cylindrical, pouch or prismatic battery. A battery can be a lithium-ion battery (LiB), for example.

[0023] The battery protection shield according to the invention initially comprises an outer layer and an inner layer. An inner layer is the layer facing the battery side, and an outer layer is the layer facing the outside, for example, the vehicle installation space. The inner and outer layers can each comprise or be made of different materials. The inner layer can be made of gas-permeable material. The outer layer can be gas-impermeable. The outer layer can be made of fire-resistant materials. The inner layer can carry the active layer.

[0024] The active layer is a layer that can possess multiple functional properties that can prevent or limit thermal runaway in a battery cell. It can consist of a first and a second agent. An agent according to the invention can, for example, be a material with specific properties. For example, specific nanomaterials can be used in the active layer as the first agent in combination with activated spheres with a large surface area as adsorbents. The thickness of the active layer can be 0.05–0.2 mm.

[0025] According to the invention, the first and second agents of the active layer have different fire protection properties upon activation. Activation here refers, for example, to exceeding a certain temperature or simply the presence of certain gases.

[0026] The first agent can, in particular, comprise an extinguishing agent. An extinguishing agent is a substance that can extinguish a fire through a cooling effect and / or through chemical flame retardancy. The second agent of the active layer can be an adsorbent for flammable substances from the battery. The different fire protection properties of the first and second agents of the active layer can thus be achieved, for example, through the fire-extinguishing properties of the first agent and the adsorption or absorption of flammable substances by the second agent.

[0027] In one embodiment, the first agent can consist of core-shell spheres filled with an extinguishing agent. Core-shell spheres can be microcapsules that can collapse and release their contents above a certain temperature and also upon ignition sources, such as sparks. The contents here are, for example, an extinguishing agent, in particular a volatile extinguishing agent. The extinguishing agent can be, for example, perfluoro(2-methyl-3-pentanone).

[0028] In a further embodiment, the second means of the active layer can comprise means for gas adsorption and / or gas adsorption. As already mentioned above, gases are produced in the battery, which can trigger and / or propagate a fire in a battery cell. Such gases are, on the one hand, O 2 and H 2 , on the other hand CO 2 and CO, but above all highly flammable volatile hydrocarbons such as CH 4 , C 2 H6 and C 2 H 4 , but also oxidized organic molecules, such as those that can form in LiB, e.g. methylene carbonate, ethylene oxide and the like.

[0029] The gas adsorption and / or gas absorption agent serves to bind the flammable or fire-propagating gases so that they are not available for a potential chain reaction with one another. The gas adsorption agent does not have to be uniform; several different adsorbents can be used as the second agent according to the invention, each with different fire protection properties compared to the first agent. The gas adsorption agents corresponding to the second agent of the active layer can be nanomaterials that effect the catalytic degradation and conversion of various gases, which are generated, for example, during the charging and discharging cycles of the batteries, both through physisorption and through chemisorption processes, such as promoted oxidation, hydrolysis reactions, oxygen binding, and the like.

[0030] In a further embodiment, the gas adsorption agent may comprise activated carbon spheres, silica gel, zeolite spheres, metal oxides and polymers.

[0031] Activated carbon spheres (ACS) can be, for example, activated carbon spheres that are particularly suitable for absorbing volatile, short-chain hydrocarbons such as CH 4 , C 2 H 6 and C 2 H 4 , such as those that can arise in a LiB. The ACS are also suitable for CO 2 and other oxidized organic molecules, such as methylene carbonate and ethylene oxide. Furthermore, the ACS can adsorb water molecules, i.e., the water vapor produced by high temperatures in the battery.

[0032] Furthermore, and preferably, the water vapor generated in the LiB can be adsorbed by silica gel. Silica gel can be obtained by acidifying an aqueous solution of sodium silicate. Silica can be produced in spherical or irregular form, with a particle size of 1-2 mm. The silica gel spheres can also have a pore size of up to 2-3 nm, thus providing a large active surface area of ​​750-800 m². 2 / g for moisture adsorption. The ability of silica gel spheres to absorb moisture is based on the large surface area created by the surface pores and the interstitial micropores containing capillary channels. Water molecules can be drawn into the channels by the capillary action of the micropores and their capillary channels, where they can be stored until possible later release.

[0033] The gas adsorption agent may also contain zeolite spheres. Zeolite spheres may be porous zeolite spheres. Zeolites are crystalline aluminosilicates and correspond to a microporous rock form, which is suitable for, for example, CO 2 Zeolites are also known as "molecular sieves" because they have a cavity structure inside, which in turn can contain many interconnected pores of uniform size. Such zeolite molecular sieves are available in four common sizes, designated 3A, 4A, 5A, and 13X, and are used here for the adsorption of CO 2 or steam. Zeolites can have an adsorption capacity for CO 2of > 0.12 g / g. Furthermore, the zeolites can act synergistically with the activated carbon spheres, especially when a complex gas mixture escapes from the LiB, which can contain both polar and apolar organic and inorganic compounds.

[0034] Furthermore, the gas adsorption agents can comprise metal oxides. The metal oxides used can be different and have different adsorption effects. An adsorption effect here also includes a catalytic reaction on the metal oxide surface, such as catalytic oxidation.

[0035] The metal oxides can be in the form of granular or porous metal oxide spheres. For example, hopcalite spheres can be used. Hopcalite consists of copper oxides and manganese oxides and can be used to convert CO to CO. 2to oxidize. The hopcalite used can be doped with other metals such as gold, silver, cerium, or cobalt to improve its redox behavior, for example, with a proportion of <10 wt.%. For example, for the oxidation of CO, oxygen is first adsorbed onto the surface of the CuMnOx catalyst (corresponding to a metal oxide used according to the invention); the activation energy required for this is reduced by doping the hopcalite with, for example, Au, Ag, Ce, or Co. The adsorbed oxygen on the CuMnOx catalyst then leads to the oxidation of the CO to CO 2 . The CO 2 can then be adsorbed, for example, by the zeolite materials described above.

[0036] Metal oxides can also be used for the absorption or reductive removal of oxygen. For example, (divalent) FeO is suitable here, which in the presence of oxygen converts to (trivalent) Fe 2 OS oxidized.

[0037] In addition, polyphenols such as pyrogallol can be used to adsorb or remove the oxygen contained in the resulting gas mixture. Pyrogallol reacts in the presence of oxygen to form the yellowish, reddish, or brown-colored agent purpurogallin.

[0038] Polymers, for example, in powder form, can be used to absorb the highly flammable hydrogen produced in the battery. Acid-doped polyaniline and polypyrrole, for example, are suitable for this purpose. The acid doping leads to a charge on the amine groups, where the gaseous hydrogen molecules can dissociate and bind.

[0039] Accordingly, the adsorbents described here can be used for the adsorption and absorption of gases generated in the LiB, which can lead to thermal runaway of the battery, thereby reducing the risk of fire. Furthermore, the gas adsorption agents described here are not limited to a selective effect. The gas adsorption agents used can act synergistically.

[0040] The materials described here or the active layer agents according to the invention—the nanomaterials as well as the porous adsorption materials—are, for example, granular in their initial state. The agents used here can have a grain size of 0.1–3 mm, preferably 0.2–1.5 mm. However, the materials used here can also be present in other forms. The materials can be selected in their shape to suit a corresponding manufacturing process.

[0041] In one embodiment, the active layer agents are incorporated into a common layer. This means that the above-described active layer agents can be incorporated as powder either into a binder matrix or applied to the inner layer as a carrier layer. The agents are distributed isotropically in the active layer.

[0042] Furthermore, the individual means for gas adsorption, gas absorption and the extinguishing agent according to the invention - i.e. generally the first and second means (which may consist of several means) with different fire protection properties each - can be introduced into the active layer as individual homogeneous layers.

[0043] In a further embodiment of the battery protection shield according to the invention, the inner layer can have a fiber structure and the outer layer can have a fire-resistant material.

[0044] The inner layer is aligned with the battery's outer shell and can support the active layer. Accordingly, the inner layer is permeable to the gases generated in the battery. Furthermore, the inner layer can consist of a fiber structure that is tear-resistant and is available in various densities as a nonwoven, or in various fiber and pore sizes as a fiber fabric. Rip-stop textiles, for example, can be used for the inner layer. A commercially available rip-stop textile has a checkerboard structure, created by a weaving technique that uses two different yarn thicknesses. The inner layer can also be an adsorptive carbon fabric, which can consist of woven or nonwoven precursors. In addition to the active layer, the carbon fabric of the inner layer can adsorb the gas generated in the LiB.

[0045] The outer layer can preferably be made of a fire-resistant material. The outer layer is the layer of the battery protection shield according to the invention that is farthest from the battery and can serve as a safety layer that, for example, inhibits, contains, or extinguishes fires that may arise in the battery. The outer layer can be made of a film made of a fire-retardant material.

[0046] Furthermore, the outer layer can consist of a flame-retardant cotton or aramid fiber fabric. Cotton fabrics are suitable as a material for the outer layer due to their advantageous properties in terms of thermal insulation, biocompatibility, high moisture absorption, and breathability. Aramid fibers, short for aromatic polyamide, can be used as the outer layer of the fire protection screen according to the invention due to their mechanical stability, their melting point of > 500°C, and their low flammability. The outer layer can have a thickness of 1-5 mm, preferably 1-3 mm.

[0047] The inner layer, the active layer and the outer layer can be laminated to form a composite, for example at temperatures of 50 to 120°C.

[0048] In further embodiments, the fire protection shield can be designed as a flexible fabric or as a solid structure. It can be designed so flexibly, for example, as a kind of protective blanket, that it can be applied to all types of battery cells, modules, or systems.

[0049] Furthermore, the fire shield can be designed as a rigid structure, for example, in the form of a case, which serves to cover the entire battery unit with the fire shield housed in the case. By using a rigid structure for the fire shield according to the invention, greater mechanical stability of the fire shield can be ensured if necessary.

[0050] The fire protection shield according to the invention can accordingly be understood as a multi-layer, multi-component protective textile, which has optionally been incorporated into a rigid structure that encloses the battery cells and / or the battery. The fire protection shield as a textile can, for example, have a total thickness of 1-8 mm, preferably 2-5 mm.

[0051] The fire protection shield can be designed as a molded body. The molded body designed as a fire protection shield can have different wall thicknesses.

[0052] In a further embodiment, the present invention relates to a battery assembly with a fire shield having one of the properties described above.

[0053] In a further embodiment, the present invention relates to a vehicle comprising a battery arrangement as described above.

[0054] The fire protection shield according to the invention can prevent thermal runaway of the battery. Furthermore, the adsorptive and absorptive materials used reduce the release of toxic gases from the battery.

[0055] Embodiments of the invention will now be described by way of example and with reference to the accompanying drawings, in which: Fig. 1 shows schematically the structure of a vehicle battery; Fig. 2a schematically shows an embodiment of the fire protection screen according to the invention; Fig. 2b schematically shows another embodiment of the fire protection screen according to the invention; Fig. 3a schematically shows another embodiment of the fire protection screen according to the invention; Fig. 3b schematically illustrates an embodiment of the active layer Fig. 4 schematically shows another embodiment of the fire protection screen according to the invention;

[0056] In the Fig. 1 schematically shows a battery in the form of a battery system (10), for example a vehicle battery, for which the fire protection screen (30) according to the invention can be used.

[0057] The battery in the Fig. 1 comprises individual battery cells (12), for example lithium-ion battery cells such as nickel-manganese-cobalt batteries (NMC), lithium iron phosphate batteries (LFP), lithium magnesium oxide batteries, and the like. Several battery cells (12) form a battery module (11). The battery modules (11) form the battery system (10).

[0058] An embodiment of a fire protection screen (30) according to the invention is shown in Fig. 2a. The fire protection screen (30) in the Fig. 2a is designed as a flexible protective blanket. The protective blanket can enclose the battery system (10) on at least three sides. The fire protection shield (30) can be the protective blanket itself. Furthermore, the fire protection shield (30) can be incorporated into the protective blanket. In an embodiment not shown, the fire protection shield (30) can also be applied over the individual battery modules (11) or the individual battery cells (12).

[0059] A further embodiment of the fire protection screen according to the invention is described in Fig. 2b. Here, the fire protection shield (30) is incorporated into a rigid structure, for example in the form of a box-shaped cover (20), which precisely encloses the battery system (10). The fire protection shield (30) can also have a shape similar to a suitcase, in which the box-shaped cover (20) also has a lid (21), which can optionally be provided with the fire protection shield (30), whereby the battery system (10) is surrounded by the fire protection shield (30) on four sides. In an embodiment not shown, the rigid fire protection shield (30) designed in this way can also be applied over the individual battery modules (11) or even the individual battery cells (12).

[0060] The Fig. Figure 3a shows an embodiment of the individual layers - inner (31), active (32) and outer (33) layer - of the fire protection screen (30) according to the invention.

[0061] The inner layer (31) faces the battery system (10) and can rest directly on it. On the side of the inner layer (31) not facing the battery system (10) is the active layer (32), which, for example, comprises a first agent (40) with a fire protection effect. This first agent (40) can, for example, comprise an extinguishing agent.

[0062] The first means can be configured in the form of core-shell spheres (40) filled with an extinguishing agent. The extinguishing agent is preferably a volatile extinguishing agent. The core-shell spheres are microcapsules designed, for example, to collapse at an activation temperature of approximately 230°C, thus releasing the extinguishing agent, allowing a fire in the battery cell to be actively extinguished.

[0063] The active layer further comprises a second or further agent (50) that has a fire protection effect that differs from the first agent (40). The different fire protection effect of the second or further agent (50) compared to the first agent (40) of the active layer (32) can, for example, be an effect in which combustible gases generated in the battery system (10) are adsorbed, absorbed, or otherwise chemically converted, or physically and chemically bound.

[0064] The active layer is followed by the outer layer (33). The outer layer (33) is made of a fireproof material, for example.

[0065] The Fig. Figure 3b shows a detailed view of an embodiment of the active layer (32). The active layer in the Fig. 3b comprises the first means (40), which can be an extinguishing agent. The second means (50) is in the Fig. 3b in the form of six different, further, or second agents (51, 52, 53, 54, 55, 56) having the properties of adsorption, absorption, chemical conversion, and / or physico-chemical bonding. For example, in addition to the first agent (40) with fire protection effect, for example an extinguishing agent, the active layer (32) can comprise activated carbon spheres (51), zeolite spheres (52), metal oxide spheres (53), silica gel (54), iron(II) oxide particles (55), and an amine-containing organic polymer (56) individually, preferably in combination, as the second agent (50).

[0066] A fire protection screen (30) according to the invention, comprising an active layer (32) such as that described in Fig. 3b, can be applied to a battery system (10) which, during a full charge or discharge cycle at 60°C, can have a gas mixture with the following exemplary composition: H 2 0-30%vol, O 2 0-5 %vol, CO 0-50 %vol, CO2 0-80 %vol and total hydrocarbons (e.g. CH 4 , C 2 H 2 , C 2 H 4 , C 2 H 6 , C 3 H 8 and the like) 0-70 %vol.

[0067] A fire protection shield for such a battery system can be manufactured as follows: for the active layer (32), 3 - 30 g of activated carbon spheres (51) are used to adsorb hydrocarbons, 3 - 30 g of zeolite spheres (52) are used for the CO 2 -adsorption, 5-20 g metal oxides (53) for CO removal, 5-10 g silica gel (54) for water vapor removal, 1-2 g chemicals, such as FeO particles for oxygen removal (55), 5-10 g polymers for H 2 -binding (56) and 1-5 g structured core-shell spheres (40) filled with an extinguishing agent are mixed together and laminated with the inner (31) and outer layer (33).

[0068] In the Fig. A further embodiment of the fire protection screen (30) according to the invention is shown. In contrast to the embodiment of the Fig. 3b shown active layer (32) is in the embodiment of Fig. 4, the active layer (32) is also multilayered. The first agent (40) and the second agent(s) (50) are each incorporated into the active layer (32) as individual layers. Thus, the individual layers are separated from each other by a porous cotton or cellulose fabric (41) with a thickness of, for example, 0.05 - 0.2 mm.

[0069] The one in the Fig. The structure of the fire protection screen according to the invention shown in Figure 4 is composed as follows: The inner layer (31) consists of a carbon fabric. The first layer of the active layer (32) is applied to this, which here consists of a polymer for removing H 2(56), for example, acid-doped polyaniline, and silica gel (54) for water vapor removal. This layer is followed by the next layer of the active layer (32), which consists of core-shell spheres (40) filled with an extinguishing agent and FeO particles (55) for the reduction of O 2 , which are applied to a cellulose fabric (41). This layer is followed by a layer of activated carbon spheres (51) to remove hydrocarbons. This layer is followed by a layer of metal oxide spheres (53) to remove CO. This layer is followed by a layer of zeolite spheres (54) to also remove the CO formed in the underlying metal oxide layer (53). 2 , coming from the oxidation of CO to CO 2to adsorb. These layers are closed by the outer layer (33), which can be made of, for example, an aramid fiber. The inner, active, and outer layers are laminated in this way as one embodiment of the fire protection screen according to the invention.

[0070] By designing the active layer in this way, the fire retardants used can be used synergistically. List of reference symbols 10 Battery system 11 Battery module 12 battery cells 20 Cover 21 lids 30 fire protection screen 31 inner layer 32 active layer 33 outer layer 40 first means / core-shell spheres 41 Cellulose fabrics 50 second remedy 51 activated carbon spheres 52 zeolite spheres 53 metal oxide spheres 54 silica gel 55 FeO particles 56 Polymer QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] EP 3 352 286 A1

[0007] EP 3 327 854 A1

[0008] US 2010 / 0255359 A1

[0009] US 2016 / 0218336 A1

[0010] EP 4 057 370 A2

[0012] WO 2020 / 047 846 A1

[0013] US 2006 / 068 278 A1

[0014] WO 2019 / 121 641 A1

[0015]

Claims

[1] Fire protection screen (30) for a battery cell, comprising - an inner layer (31), - an active layer (32), and - an outer layer (33), wherein the active layer comprises a first agent (40), in particular an extinguishing agent, and a second agent (50), wherein the first and the second agent exhibit different fire protection effects when activated. [2] Fire protection screen (30) according to claim 1, wherein the first means (40) comprises core-shell spheres filled with an extinguishing agent. [3] Fire protection screen (30) according to one of claims 1 and 2, wherein the second means (50) of the active layer comprises means for gas adsorption and / or gas absorption. [4] Fire protection screen (30) according to claim 3, wherein the means for gas adsorption and / or gas absorption comprise activated carbon spheres (51), silica gel (54), zeolite spheres (52), metal oxides (53; 55) and polymers (56). [5] Fire protection screen (30) according to one of the preceding claims, wherein the means of the active layer (32) are incorporated in a common layer. [6] Fire protection screen (30) according to one of the preceding claims, wherein the means of the active layer (32) are introduced individually as individual layers. [7] Fire protection screen according to one of the preceding claims, wherein the inner layer (31) has a fibrous structure and the outer layer (33) has a fire-resistant material. [8] Fire protection screen (30) according to one of the preceding claims, wherein the fire protection screen (30) is designed as a flexible fabric or as a solid structure. [9] Battery arrangement (10) with a fire protection screen (30) according to one of claims 1 to 8. [10] A vehicle comprising a battery assembly (10) according to claim 9.

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