Battery housing cover with a fibre composite with an oxide matrix

Abstract

The invention relates to a battery housing cover (10) for covering at least one battery cell (26), wherein the battery housing cover (10) comprises a fibre composite with an oxide matrix. The invention also relates to a layer system (14) for a battery housing cover (10) with a first layer (16) made of a fibre composite with an oxide matrix and a second layer (18) made of a thermally insulating material. The invention further relates to the use of a fibre composite with an oxide matrix for a battery housing cover (10), a method for producing a layer system (14) and a method for producing a battery housing cover (10).

Description

[0001] Battery housing cover with fiber composite with oxide matrix

[0002] The invention relates to a battery housing cover according to the preamble of claim 1. Furthermore, the invention relates to an arrangement comprising a battery cell and a battery housing according to claim 13 and to an electric vehicle having such an arrangement according to claim 14. The invention further relates to a layer system according to claim 15, a use of a fiber composite with an oxide matrix according to claim 18, a method for producing a layer system according to claim 19, and a method for producing a battery housing cover according to claim 21.

[0003] With the increasing popularity of electric cars, the issue of fire safety is becoming increasingly important. This is due to the fact that lithium-ion battery cells used to power a vehicle can generate particularly intense heat in the event of a fire. In the event of thermal runaway of a battery cell, the excess pressure built up within it is released through a pressure relief valve. This means that the pressure relief valve opens and releases a hot, supersonic gas stream, sometimes containing metallic particles and / or soot, into the environment. The gas stream escapes through the pressure relief valve in a directed jet that spreads out in a cone shape. The temperature of the gas can exceed 1200 °C.The hot gases and the particles present in the gas can perforate the battery housing cover and cause life-threatening flames and smoke to penetrate the vehicle's passenger compartment, as battery systems are often located beneath the passenger compartment. Furthermore, if one battery cell catches fire, neighboring battery cells often also catch fire.

[0004] There are regulations (for example, GTR20; Global Technical Regulation on Electric Vehicle Safety - EVS) that stipulate that in the event of a fire involving at least one battery cell, the occupants in the passenger compartment are protected for at least five minutes. Accordingly, the penetration of flames and smoke must be prevented for that time.

[0005] The underlying object of the invention is therefore to provide a battery housing cover, a layer system, an arrangement, an electric vehicle, the use of a fiber composite with an oxide matrix and methods for producing a layer system and for producing a battery housing cover, which are suitable for enabling particularly good protection of the occupants in a vehicle.

[0006] The object is achieved according to the invention with the features of the independent claims. Further advantages and practical embodiments are explained in connection with the dependent claims.

[0007] A battery housing cover according to the invention serves to cover at least one battery cell. The battery housing cover can be part of a multi-part battery housing, wherein at least one battery cell can be accommodated in the battery housing. In particular, the battery cell is a lithium-ion battery. The battery housing cover can be designed in particular as a plate or as a base pan. In particular, this is a battery housing cover for arrangement in an electric vehicle, wherein one or more battery cells for supplying power to an electric vehicle are covered by the battery housing cover. In the vehicle, the battery housing cover can be arranged above the at least one battery cell, viewed in the vertical direction of the vehicle, or else arranged below the at least one battery cell.The battery housing cover is arranged such that it is positioned in an outlet direction of a pressure relief valve or a rupture disc of a battery cell.

[0008] According to the invention, the battery housing cover comprises a fiber composite with an oxide matrix. In particular, the battery housing cover comprises an oxide-ceramic composite material. An oxide-ceramic composite material is also commonly referred to as an oxide-ceramic matrix composite (OCMC).

[0009] Such a fiber composite with an oxide matrix comprises, in particular, a plurality of fibers. The fibers are, in particular, oxide-ceramic multifilament fibers. Alternatively, they can also be silicate fibers, in particular glass fibers, carbon, or mineral fibers. In the context of the present invention, silicate fibers are understood to mean fibers that consist predominantly of SiO2. The SiO2 content is, in particular, at least 90% and preferably at least 94%. The SiO2 content can be up to 99.95 wt. In addition to SiO2, glass fibers contain a certain proportion of Al2O3 and can also contain other components such as MgO, B2O3, or CaO. The glass fibers can, in particular, also be so-called E-glass fibers, comprising or consisting of aluminum borosilicate glass. Glass fibers, in particular, have the advantage of being particularly cost-effective while having similar properties.The fibers are embedded in a matrix (also called slurry). The oxide-ceramic multifilament fibers can be continuous oxide-ceramic fibers and / or short oxide-ceramic fibers. Silicate fibers can also be continuous fibers or short fibers. Continuous fibers have a length in the range of many tens of centimeters to many meters. Short fibers have a length in the range of a few millimeters to a few centimeters. A fiber referred to here is in particular a fiber bundle (roving) which comprises a large number of individual fibers. The matrix can also be an oxide-ceramic material. The oxide-ceramic fibers and / or the oxide-ceramic matrix are composed in particular of aluminum oxide, mullite or a mixture of aluminum oxide and mullite. According to an advantageous embodiment, the fibers can be composed of 60 to 100 wt.% aluminum oxide and 0 to 40 wt.%-% silicon dioxide. The matrix can in particular consist of 70 to 100 wt.% aluminum oxide and 0 to 30 wt.% silicon dioxide.

[0010] Fiber composites with an oxide matrix, and in particular oxide-ceramic composites or composites with silicate fibers, are known for their high thermal (cycling) resistance, chemical resistance, and mechanical shock resistance. These exhibit sufficient resistance at temperatures up to 1300°C. Fiber composites with an oxide matrix, and in particular oxide-ceramic composites, are also suitable for applications subject to thermal shock. The material can withstand temperature gradients of up to 1000°C / sec or 1000°C / cm. Fiber composites with an oxide matrix are also insensitive to mechanical shock loads, vibrations, and cyclic loading. When used in a battery housing cover, this material can withstand the hot, particulate, directed gas flow escaping from a battery cell.For example, it has already been achieved that, when gases escape at 1200°C, the temperature on the outside of the battery housing cover is only 200°C maximum through a suitable arrangement of the oxide-ceramic composite material. This effectively protects surrounding vehicle components, especially the passenger compartment, and provides sufficient time for vehicle occupants to exit the vehicle.

[0011] A fiber composite with an oxide matrix as described above has the further advantage that a deformable, yet flexible, flat material can be initially produced in the ceramic green state, which is adaptable to various surfaces. It can also be easily transported and used at an application site in a wet state. Fiber composites with an oxide matrix, and especially oxide-ceramic composites such as mullitic composites, have the advantage of being mechanically stable and transportable even in the dried, but still unsintered, state (green compact).

[0012] In particular, the fiber composite with an oxide matrix is ​​a nonwoven-based fiber composite with an oxide matrix, and in particular, a nonwoven-based oxide-ceramic composite material. In particular, it is a nonwoven made of individual ceramic fibers or a silicate nonwoven. The fibers are generally short fibers. The advantage of these nonwovens is that they are more cost-effective than composite materials made of continuous fibers, as they can be produced from cutting residues, among other things. Furthermore, such short-fiber nonwovens are mechanically stable and easily deformable in their green state.

[0013] In a practical embodiment, the battery housing cover has a base body, which can be made of metal, such as alloyed steel or aluminum, or of glass fiber reinforced plastic (GRP) or carbon fiber reinforced plastic (CFRP). At least one section of the fiber composite with an oxide matrix is ​​then arranged on the base body. The section can extend over the base body so that it is completely lined from the inside. In the case of a base body made of GRP / CFRP, the section can also be embedded or laminated into the base body.

[0014] The at least one section made of fiber composite with an oxide matrix is ​​in particular strip-shaped. In this case, strip-shaped means that the section has a longitudinal extent that is at least as great as its transverse extent. In particular, the section is designed such that it extends over several pressure relief valves of battery cells arranged in a row. A strip in this case has in particular a width of at least 50 mm. The length depends in particular on the arrangement of the battery cells. Alternatively, a section is designed such that it extends over only one pressure relief valve, for example with a circular geometry in order to be adapted as far as possible to the gas flow that has a round cross-section and escapes from a pressure relief valve. In this case, the diameter is in particular at least 25 mm.

[0015] As an alternative to arranging a section on the base body, it is also conceivable that the entire battery housing cover is made of fiber composite with an oxide matrix and in particular of oxide-ceramic fiber composite material or at least part of the base body is made of fiber composite with an oxide matrix.

[0016] The described purely local reinforcement, in which only a strip or circular section is arranged on the base body, is particularly suitable for prismatic or round cells. For pouch cells, battery housing covers made entirely of or fully lined with an oxide-ceramic composite material are suitable.

[0017] In particular, the section with the fiber composite with an oxide matrix is ​​firmly bonded to the base body. This allows the fiber composite with an oxide matrix to be glued to the base body. Suitable adhesives include conventional spray or instant adhesives. Bonding represents a simple method of joining in this case.

[0018] Alternatively, the section containing the fiber composite with an oxide matrix can also be laminated into the base body. This is particularly possible if the base body is made of CFRP or GFRP.

[0019] A particularly cost-effective solution is when the fiber composite with an oxide matrix is ​​fastened to the base body in a force-fitting manner, for example by clamping or screwing. In a further practical embodiment of the battery housing cover, the fiber composite with an oxide matrix, and in particular an oxide-ceramic composite material, forms a first layer and a second layer made of a thermally insulating material is arranged on the side of the first layer facing the inside of the battery housing cover, i.e. on a side facing the at least one battery cell and in particular facing away from a base body. The thermally insulating material serves in particular as a thermal barrier for the heat generated in the event of a fire in one or more battery cells. Secondly, the thermally insulating material can act as a soot catcher.This is particularly relevant to avoid short circuits on electrical conductors or other battery cells inside the battery system.

[0020] Alternatively, the order of the layers on the base body of the battery housing cover can also be reversed, so a second layer of a thermally insulating material can be arranged between the first layer of the fiber composite with an oxide matrix and the base body. In this case, the first layer of fiber composite with an oxide matrix facing the battery cell serves as the mechanical shielding of the battery housing exterior, and the thermally insulating material arranged between them acts as a thermal barrier.

[0021] The layer thickness of the first layer of the fiber composite with an oxide matrix is ​​in particular at least 0.3 mm and preferably at least 0.5 mm. The layer thickness of the first layer is in particular between 0.3 mm and 3 mm and preferably between 0.4 mm and 2 mm.

[0022] The layer thickness of the second layer of thermally insulating material is in particular at least 1 mm and preferably at least 3 mm. The layer thickness of the second layer is in particular between 1 mm and 8 mm and preferably between 3 mm and 6 mm.

[0023] The total layer thickness of the first and second layers can be adjusted depending on the available installation space and safety requirements. With the described two-layer system, total layer thicknesses of less than 1.8 mm were achieved, meeting safety requirements. The layer thickness of the fiber composite with an oxide matrix is ​​0.6 mm to 0.8 mm, and the layer thickness of the thermally insulating material is 1 mm. The layer thicknesses of the respective layers can be determined using scanning electron microscopy (SEM) or computed tomography (CT).

[0024] The thermally insulating material is in particular a material which can withstand temperatures of at least 1000°C in the short term - such as silica or silica with mica or mica - and preferably withstands temperatures of at least 1000°C in the long term (ie over 15 minutes) - such as mullitic materials.

[0025] In particular, the thermally insulating material is needle-punched nonwoven or needle-felt. In particular, the thermally insulating fiber material is an oxide-ceramic or mullite material made of silicon dioxide and aluminum oxide. Alternatively, it is a silica-based nonwoven. The nonwoven comprises, in particular, short mullite fibers that are needle-punched to form a nonwoven. The short fibers are, in particular, 3 mm to 50 mm long. In particular, the insulating fiber material is binder-free. The material marketed under the Maftec™ brand by Mitsubishi Chemical Corp. or the material marketed under the Fibermax™ brand by ME Schupp Industriekeramik GmbH have proven particularly suitable. The thermally insulating material is, in particular, a mat-shaped material containing oxide-ceramic short fibers made of Al2O3 and / or mullite.All of the above fiber materials have the advantage that they are non-flammable and are also inexpensive and lightweight.

[0026] In order to bond the first layer of fiber composite with an oxide matrix and the second layer of thermally insulating material, a matrix is ​​arranged between them. The matrix is ​​preferably the material that is already used as a matrix for the fiber composite with an oxide matrix. If the fiber composite with an oxide matrix has not yet dried, the thermally insulating material can simply be placed on the wet first layer. The slip that has not yet dried then infiltrates the second layer, at least superficially. A first transition layer is formed. When the matrix or slip dries, the first layer of fiber composite with an oxide matrix and the second layer of thermally insulating material adhere to one another. If the fiber composite with an oxide matrix has already dried, a further layer of slip or slip can be applied.Matrix is ​​applied to bond the first layer to the second layer.

[0027] Alternatively, it is also conceivable for the first layer of fiber composite with an oxide matrix and the second layer of the thermally insulating material to be bonded together by means of an adhesive layer. In this case, the first and second layers can be bonded together in the dry state.

[0028] In a further practical embodiment, in the layer system in which the second layer of thermally insulating material faces the battery cells, a third layer of a ceramic raw material is arranged on the inner side of the second layer of thermally insulating material facing the battery cells. The inner side is the side facing away from the first layer. In particular, the ceramic raw material is mullite or a milled mullitic material. The ceramic raw material is in particular a refractory material and can withstand temperatures of over 1000°C. The third layer serves in particular as mechanical protection for the comparatively soft second layer consisting of the thermally insulating material and in particular prevents the second layer from shattering due to the hot gas flow from the failing battery cells.

[0029] Alternatively, in the layer system in which the second layer of thermally insulating material faces the battery cells, a third layer comprising a fiber composite with an oxide matrix is ​​arranged on the inner side of the second layer of thermally insulating material facing the battery cells. Such a fiber composite with an oxide matrix has, in particular, a plurality of fibers. The fibers are, in particular, oxide-ceramic multifilament fibers. Alternatively, they can also be silicate fibers, in particular glass fibers, carbon or mineral fibers. The fibers are embedded in a matrix. The fibers can be continuous fibers and / or short fibers. The third layer comprising a fiber composite with an oxide matrix is ​​connected to the second layer in particular by means of an adhesive layer. The layer thickness of the third layer is, in particular, at least 0.2 mm and preferably at least 0.5 mm.The layer thickness of the third layer is in particular between 0.2 mm and 7 mm and preferably between 0.5 mm and 5 mm.

[0030] In addition to the ceramic raw material, this third layer also contains an additive. The additive can be selected depending on the application and design of the third layer. In particular, the additive is an organic additive, especially polyvinyl alcohol (PVA). The organic additive increases the elasticity of the third layer and prevents the particles from chalking onto the ceramic raw material in the green body. A good compromise between elasticity and fire retardancy is achieved particularly with concentrations / proportions of organic additive in the third layer of 2% to 20% and in particular of 5% to 10%. A third layer containing an organic additive is well suited for beam and flame reflection, i.e. as mechanical protection for the second layer.The gas stream emitted by a battery cell does not penetrate the third layer; instead, the third layer acts as a kind of armor and reflects the beam. The third layer then largely prevents the hot gases from penetrating the thermally insulating layer and further reduces the backside temperature.

[0031] Together with the second layer and the first layer, this achieves the best possible thermal decoupling of the exterior of the battery housing cover from the battery cells. Specifically, the third layer containing the organic additive is applied as a suspension to the second layer, and the suspension infiltrates the second layer. This creates a second transition layer. In this transition layer, the concentration of the ceramic raw materials decreases over the infiltration depth. The infiltration depth can range from 10% to 90% of the layer thickness of the second layer. In particular, the layer thickness of the second transition layer is greater than the layer thickness of the aforementioned first transition layer.

[0032] Alternatively, the additive can also be water glass. Water glass also causes the third layer to become elastic, but in such a way that the material of the third layer softens when heated. This allows the gas flow to burn a hole locally into the third layer. The gas flow can then enter the second layer through a kind of crater in the third layer and spread within the second layer. The second layer therefore serves as a jet or flame catcher. In particular, soot particles are absorbed in the second layer. The second layer also serves to dampen the momentum of the gas flow and any particles it may contain. The third layer and the first layer serve to mechanically contain the gas spreading in the second layer and to provide thermal insulation.

[0033] As already mentioned above, a suspension is used in particular to apply the ceramic raw material. The ceramic raw material, in particular together with the additive, is suspended in water. The suspension is then applied to the second layer. The suspension can be applied by brushing (e.g., with a brush), spraying, spinning, or using a waterfall method. After the water evaporates, part of the ceramic raw material has penetrated into the second layer, and part remains on the surface of the second layer of thermally insulating material, forming the armor. Here, too, the infiltration depth into the second layer can range from 10% to 90% of the layer thickness of the second layer.

[0034] In particular, in the battery housing cover, the fiber composite with an oxide matrix is ​​present as a green compact. This means that the fiber composite with an oxide matrix has not yet been sintered. If a third layer comprising a ceramic raw material or a fiber composite with an oxide matrix is ​​present, this is also arranged on the battery housing cover in a green state. This has the advantage that energy-intensive sintering can be eliminated. The use of a green compact is particularly possible if the fiber composite with an oxide matrix is ​​a mullitic material, which remains elastic even in the dried state due to the organic additive and does not break or chalk. Sintering only occurs when a thermal runaway or explosion of a battery cell ('in situ') and the subsequent combustion of neighboring cells.This provides a further advantage, namely that in the event of a fire, the material can initially absorb energy for sintering. The invention also relates to an arrangement of at least one battery cell in a battery housing with a battery housing cover as described above. In particular, a plurality of battery cells are arranged in one or more rows. These can each be clamped together. Such an interconnected arrangement of a plurality of battery cells can also be referred to as a battery module. In particular, at least one battery module is arranged in a battery housing. The battery housing cover is arranged relative to the at least one battery cell in such a way that a pressure relief valve or a bursting disc is directed towards the battery housing cover and any escaping gas flow strikes the battery housing cover. The battery cell is, in particular, a lithium-ion rechargeable battery.

[0035] The invention also relates to an electric vehicle, i.e., a vehicle with an electric drive, wherein the energy for the drive is provided by at least one battery cell. The electric vehicle has an arrangement as described above.

[0036] The invention further relates to a layer system for a battery housing cover. The layer system is intended, in particular, to be designed as an insert or inlay for a battery housing cover. The layer system serves as a thermal, mechanical, and chemical barrier, so that the battery housing cover protects the environment, in particular the passenger compartment and possibly also other battery cells, from hot gases escaping from a battery cell.

[0037] The layer system comprises at least two layers: a first layer made of a fiber composite with an oxide matrix and a second layer made of a thermally insulating material. The fiber composite with an oxide matrix is, in particular, fibers and a matrix each made of oxide ceramic. The fibers can alternatively be silicate fibers. With regard to the details of the first layer, reference is hereby also made to the above description. In particular, the first layer comprises short fibers, in particular made of a mullitic material or of silicate fibers, and a mullitic matrix. The short fibers consist of one or more layers of wet-laid nonwoven fabric (wetlaicf) which has been infiltrated with the matrix. The layer thickness of the first layer is, in particular, at least 0.3 mm and preferably at least 0.5 mm and, in particular, between 0.3 mm and 3 mm and, preferably, between 0.5 mm and 2 mm.The fiber composite with oxide matrix is ​​thermally and mechanically very stable.

[0038] The layer system further comprises a second layer made of a thermally insulating material. The thermally insulating material serves in particular to minimize heat transfer from the hot gases escaping from the battery cell or generated during a subsequent battery fire to the outside of the battery housing cover – and, depending on the arrangement, to bind any smoke gases that may arise. Accordingly, the thermally insulating material has low thermal conductivity. In particular, the thermal conductivity at 1200°C is less than 0.5 W / mK and preferably less than 0.4 W / mK. The second layer has a thickness in the range of at least 1 mm and preferably at least 3 mm and in particular between 2 mm and 8 mm and preferably between 3 mm and 6 mm. The thermally insulating material is in particular short mullite fibers that are needled into a nonwoven fabric.For details on the second layer, please also refer to the above description.

[0039] The first layer and the second layer are connected, in particular, by means of an oxide-ceramic matrix. The matrix is, in particular, the mullitic matrix (the slip) of the fiber composite with an oxide matrix. A first transition layer is formed at the transition between the first layer and the second layer. Alternatively, the first layer and the second layer are connected by means of an adhesive layer.

[0040] In particular, the layer system also comprises a third layer. The third layer comprises a ceramic raw material. Alternatively, the third layer comprises a fiber composite with an oxide matrix. The third layer serves primarily to mechanically protect the rather soft second layer. The third layer consists of a monolithic material. The thickness of the third layer is in particular between 0.2 mm and 7 mm, and preferably between 0.5 mm and 5 mm.

[0041] In addition to the ceramic raw material, this third layer also contains an additive, which is an organic additive, particularly polyvinyl alcohol, or alternatively, water glass. As already described above, the properties of the third layer can be modified by adding the additives, thus achieving a different shielding behavior against hot gases. Please also refer to the above description for further details.

[0042] As described above, the third layer is applied to the second layer, particularly in the form of a suspension. Accordingly, a second transition layer is formed between the first and second layers, in which suspended ceramic raw materials and, if applicable, additives have penetrated the thermally insulating material. Depending on the suspension, a gradient of ceramic raw materials results in the second layer.

[0043] In the case that the third layer is a layer comprising a fiber composite with an oxide matrix, the third layer is connected to the second layer in particular by means of an adhesive layer.

[0044] The layer thickness of the entire layer system is in particular between 1.5 mm and 15 mm and preferably between 1.6 mm and 10 mm.

[0045] The invention further relates to the use of a fiber composite with an oxide matrix for a battery housing cover in an electric vehicle, for shielding an exterior surface against a gas flow caused by a battery cell. As already mentioned above, fiber composites with an oxide matrix offer the advantage of being very thermally and, above all, mechanically stable. In particular, the layer system described above is used for a battery housing cover.

[0046] In addition, the invention further relates to a method for producing a layer system, in particular a layer system as described above, with the following method steps:

[0047] In a first step, a first layer made of a fiber composite with an oxide matrix is ​​provided. The first layer comprises, in particular, short fibers made of an oxide-ceramic material, in particular mullite, or short silicate fibers. The first layer is preferably a wet-laid nonwoven impregnated with a slurry made of an oxide-ceramic material, also in particular mullite. In a further step, the first layer is bonded to a second layer made of a thermally insulating material (needle-punched nonwoven). The bond is made in particular by means of the slurry or matrix, which is also used for the first layer. If the slurry or matrix is ​​still wet, the second layer can simply be placed on top of the first layer and, if necessary, lightly pressed down. Alternatively, the bond can be made in the dry state by means of an adhesive layer.

[0048] Subsequently, a third layer can optionally be applied in the form of a suspension comprising a ceramic raw material. The suspension is applied, in particular, by spraying, brushing, rolling, spin coating, or using a waterfall process. The suspension can also contain at least one additive, such as, in particular, an organic additive or water glass. Depending on the desired infiltration depth (= layer thickness of the second transition layer), the composition of the suspension and the application time can be varied. Furthermore, reference is also made to the above description.

[0049] Alternatively, a fiber composite comprising an oxide matrix can be bonded to the second layer by means of an adhesive layer as a third layer.

[0050] After the layer system has been manufactured, it can be finished. This is done primarily in the green state and, if necessary, in the wet, not yet dried state. The layer system can be shaped into the desired geometry in the dry state using diamond saws or laser cutting, for example. It is also conceivable to punch the layer system in the green state.

[0051] The drying of the layer system takes place in particular at temperatures between 40°C and 80°C for 2h to 12h, depending on the process, ie whether drying takes place in a chamber dryer or in a continuous dryer that is integrated into the production unit.

[0052] The layer system can be transported in the green state and inserted into a battery housing cover as a so-called prepreg. Furthermore, the invention also relates to a method for producing a battery housing cover, wherein a section comprising a fiber composite with an oxide matrix, and in particular a section comprising silicate fibers with an oxide matrix or comprising an oxide-ceramic composite material, is arranged on a base body of a battery housing cover. In particular, the fiber composite with an oxide matrix is ​​glued, clamped, or laminated into the battery housing cover.

[0053] Preferably, the section is a layer system as described above.

[0054] In a practical embodiment of the above process, the fiber composite with an oxide matrix is ​​applied to the base body in its green state. In the event of damage, such as a battery cell fire, the fiber composite with an oxide matrix is ​​sintered only then.

[0055] Further practical embodiments and advantages are explained below in conjunction with the figures. They show:

[0056] Fig. 1 shows a section of a battery housing cover with a section of a layer system in a first embodiment in a schematic representation in cross section,

[0057] Fig. 2 shows a section of a battery housing cover with a section of a layer system in a second embodiment in a schematic representation in cross section,

[0058] Fig. 3 shows a section of a battery housing cover with a section of a layer system in a third embodiment in a schematic cross-sectional view,

[0059] Fig. 4 shows the area marked IV in Fig. 3 in a more detailed representation in a schematic cross-sectional view,

[0060] Fig. 5 shows an arrangement of the battery housing cover according to the third embodiment of Fig. 3 and a battery cell, with a first variant of a third layer in a schematic representation in cross section, and

[0061] Fig. 6 shows an arrangement of the battery housing cover according to the third embodiment from Fig. 3 and a battery cell, with a second variant of a third layer in a schematic representation in cross section.

[0062] Figures 1 to 3 illustrate various embodiments of layer systems 14. Each shows a section of a battery housing cover 10 and a layer system 14 arranged thereon. The battery housing cover 10 comprises a base body 12, which in this case is made of steel.

[0063] Fig. 1 shows a first embodiment of a layer system 14. The layer system 14 comprises a first layer 16 made of a fiber composite with an oxide matrix (in particular an oxide-ceramic composite material) and a second layer 18 made of a thermally insulating material. The first layer 16 is arranged on the inside of the base body 12, which is directed towards the inside of a battery housing, and is adjoined by the second layer 18. Details of the individual layers are explained below. In the first embodiment of the layer system 14 shown in Fig. 1, the first layer 16 represents a mechanical battery for the gas flow, and the second layer 18 provides thermal insulation and can also serve as a shock absorber and particle or soot catcher.

[0064] Fig. 2 shows a second embodiment of the layer system 14, wherein the layer system 14 also comprises a first layer 16 made of a fiber composite with an oxide matrix and a second layer 18 made of a thermally insulating material. In contrast to the first embodiment, the order of the layers is reversed here, with the second layer 18 resting against the base body and the first layer 16 facing the inside. Here, the first layer 16 also serves as a mechanical barrier and, as it were, as protection for the second layer 18, which primarily serves for thermal decoupling.

[0065] Fig. 3 shows a third embodiment of a layer system 14, wherein a layer system 14 comprising a first layer 16, a second layer 18 and a third layer 20 is arranged on the base body 12. The layers 16, 18, 20 are named in the order from outside to inside. The first layer 16 is arranged on the inside of the base body 12, which is directed towards an inside of a battery housing, followed by the second layer 18 and the third layer 20. The third layer 20 is accordingly the innermost layer and the first layer 16 is the outermost layer.

[0066] The first layer 16 of the respective layer systems 14 described in Figures 1 to 3 is made of a fiber composite with an oxide matrix. This may involve multiple layers of wet-laid nonwoven fabric made of short mullite fibers in a mullite matrix. The short fibers have a length of 5 mm to 25 mm.

[0067] The second layer 18 in each of the three embodiments shown is a layer of a thermally insulating material. The thermally insulating material consists of a needle-punched nonwoven made of mullite short fibers.

[0068] The third layer 20 according to the third embodiment shown in Fig. 3 comprises a ceramic raw material, here mullite. An additive, which is either PVA or water glass, is added to this.

[0069] The layer systems 14 shown in Figures 1 to 3 are arranged only in sections on the base body 12. In this case, the layer system 14 is glued to the base body 12.

[0070] In Fig. 4, the layer system 14 according to the third embodiment is shown again in detail, wherein the transitions between the individual layers can also be seen here. An oxide-ceramic matrix is ​​arranged between the first layer 16 and the second layer 18 as the first transition layer 22. This is material from the matrix of the first layer 16. The layer thickness of the first transition layer 22 is designated by di. This also corresponds to the material transition as it is formed in the first embodiment in Fig. 1 and the second embodiment in Fig. 2. A second transition layer 24 is formed between the second layer 18 and third layer 20. This second transition layer 24 is formed by infiltration when the third layer 20 is applied in the form of a suspension to the second layer 18. Depending on the duration of application and the viscosity of the suspension, the layer thickness d2 of the second transition layer 24 orthe infiltration depth of the suspension into the second layer 18 can be varied.

[0071] In the embodiment shown, the layer thickness d2 of the second transition layer 24 is greater than the layer thickness di of the first transition layer 22.

[0072] In conjunction with Fig. 5 and 6, the functioning of the layer system 14 as mechanical and thermal protection for the battery housing cover 10 is explained below.

[0073] In Fig. 5, a layer system 14 according to the third embodiment is arranged on the base body 12, with the third layer 20 being present in a first variant. This first variant of the third layer 20 comprises PVA as an additive. The PVA makes the third layer 20, comprising ceramic raw material, elastic, while remaining mechanically stable. The second transition layer 24 has a large thickness d2, so that the second layer 20 is infiltrated over a portion, i.e., 30% to 50% of its layer thickness.

[0074] In this respect, this third layer 20, according to the first embodiment of the layer system 14, serves as a kind of armor for the second layer 18. This is visualized by arrows 28, which are intended to show the gas flow escaping from a battery cell 26. The gas flow 28 expands conically outward. This gas flow 28, which may also contain particles, is reflected by the third layer 20 and redirected to the side. The third layer 20 serves as mechanical protection, while the second layer 18 and first layer 16 primarily serve to thermally insulate the exterior of the battery housing cover 10.

[0075] As can be seen in Fig. 5, the battery cell 26 emits the gas stream with a finite aperture. The gas stream 28 is reflected by the third layer 20, allowing the battery cell 26 itself as well as neighboring cells to be "hit." However, damage to the thermal insulation material (second layer 18) by particles is largely avoided. As a result, the backside temperatures on the outside of the battery housing cover remain below 150-200°C.

[0076] Fig. 6 also shows the layer system 14 according to the third embodiment, with a second variant of the third layer 20. This second variant of the third layer 20 differs from the first variant essentially in the additive in the third layer 20. The additive here is water glass. This also results in elasticity of the third layer 20 with the other ceramic raw material. Furthermore, the material can be melted locally by heat. The infiltration depth, i.e., the layer thickness d2 of the second transition layer 24, is 30 to 50% of the layer thickness of the second layer 18.

[0077] A gas stream 28 emerging from a battery cell 26 can then melt the third layer 20, allowing the gas stream 28 to penetrate the second layer 18. The gas stream 28 then spreads laterally within the second layer 18. Any soot particles and metallic particles are trapped in the second layer 18. Furthermore, the gas stream 28 in the second layer 18 is directed by the third layer 20 and the first layer 16, preventing it from spreading inward or outward. The first layer 16 and the third layer 20 reflect the gas stream 28 within the second layer 18. Thermal insulation is further provided by the second layer 18 and the first layer 16. The third layer 20 also provides mechanical stabilization for the second layer 18.

[0078] As clearly visible in Fig. 6, the thermokinetic effect of the hot gas stream 28 creates an opening 30 in the third layer 20. A portion of the gas stream 28 enters the first layer 16 almost perpendicularly, which protects the base body 12 of the battery housing cover 10. A portion of the gas stream 28 is deflected laterally and "braked" in the second layer 18. The combustion products, such as soot particles, remain in the second layer 18, and the neighboring cells are protected from hot gases.

[0079] In all embodiments shown, the layer system 14 is arranged as a green compact on the base body 12. Sintering may, if necessary, only occur through the impact of the hot gas stream 28. List of reference symbols

[0080] 10 Battery housing cover 12 Base body

[0081] 14 Shift system / section

[0082] 16 first layer (made of oxide ceramic composite material)

[0083] 18 second layer (made of thermally insulating material)

[0084] 20 third layer (comprising ceramic raw material) 22 first transition layer

[0085] 24 second transition layer

[0086] 26 battery cells

[0087] 28 Gas flow

[0088] 30 Opening

Claims

Patent claims 1. Battery housing cover for covering at least one battery cell (26), characterized in that the battery housing cover (10) comprises a fiber composite with an oxide matrix.

2. Battery housing cover according to the preceding claim, characterized in that the battery housing cover (10) comprises a nonwoven-based fiber composite with an oxide matrix.

3. Battery housing cover according to one of the preceding claims, characterized in that the battery housing cover (10) has a base body (12) and at least one section (14) comprising the fiber composite with an oxide matrix is ​​arranged on the base body (12).

4. Battery housing cover according to the preceding claim, characterized in that the fiber composite with oxide matrix is ​​materially connected to the base body (12).

5. Battery housing cover according to one of the preceding claims, characterized in that a first layer (16) comprising the fiber composite with an oxide matrix is ​​arranged on a side facing the inside of the battery housing cover (10), and a second layer (18) made of a thermally insulating material is arranged on the side of the first layer (16) facing away from the battery housing cover (10).

6. Battery housing cover according to one of the preceding claims 1 to 4, characterized in that a second layer (18) made of a thermally insulating material is arranged between a first layer (16) comprising the fiber composite with an oxide matrix and the battery housing cover (10).

7. Battery housing cover according to one of the two preceding claims, characterized in that the thermally insulating material is a fleece or felt.

8. Battery housing cover according to one of the three preceding claims, characterized in that a matrix is ​​arranged between the first layer (16) of fiber composite with oxide matrix and the second layer (18) of the thermally insulating material, for connecting the first layer (16) and the second layer (18).

9. Battery housing cover according to one of the preceding claims 5 to 7, characterized in that an adhesive layer is arranged between the first layer (16) of fiber composite with oxide matrix and the second layer (18) of the thermally insulating material, for connecting the first layer (16) and the second layer (18).

10. Battery housing cover according to one of the preceding claims 5 and 7 to 8, characterized in that a third layer (20) comprising a ceramic raw material is arranged on the side of the second layer (18) of thermally insulating material facing the inside.

11. Battery housing cover according to one of the preceding claims 5 and 7 to 8, characterized in that a third layer (20) comprising a fiber composite with an oxide matrix is ​​arranged on the side of the second layer (18) of thermally insulating material facing the inside.

12. Battery housing cover according to one of the preceding claims, characterized in that the fiber composite with oxide matrix is ​​present as a green compact.

13. Arrangement of at least one battery cell (26) in a battery housing with a battery housing cover (10) according to one of the preceding claims 1 to 12.

14. Electric vehicle with an arrangement according to claim 13.

15. Layer system for a battery housing cover (10) with a first layer (16) made of a fiber composite with an oxide matrix and a second layer (18) made of a thermally insulating material.

16. Layer system according to the preceding claim, characterized in that it additionally has a third layer (20) comprising a ceramic raw material and / or a fiber composite with an oxide matrix.

17. Layer system according to one of the two preceding claims, characterized in that the third layer (20) further comprises an additive, wherein the additive comprises an organic additive and / or water glass.

18. Use of a fiber composite with an oxide matrix for a battery housing cover (10) in an electric vehicle.

19. A method for producing a layer system (14) comprising the following process steps: a) providing a first layer (16) made of a fiber composite with an oxide matrix, b) bonding the first layer (16) to a second layer (18) made of a thermally insulating material.

20. Method according to the preceding claim, characterized in that after step b) a third layer (20) is applied to the second layer (18), wherein the third layer (20) is applied in the form of a suspension comprising a ceramic raw material and / or wherein the third layer is arranged by means of an adhesive layer.

21. Experience for producing a battery housing cover (10), characterized in that a section (14) comprising a fiber composite with an oxide matrix is ​​arranged on a base body (12) of the battery housing cover (10).

22. Experience according to the preceding claim, characterized in that the fiber composite with oxidic matrix is ​​arranged in the green state on the base body (12).

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