Heat conduction and battery arrangement

Abstract

Heat conduction arrangement (1) with a heat conduction core (2) and at least one metallic heat conduction layer (3) adjacent to this heat conduction core (2), wherein the heat conduction core (2) consists of a metal fiber composite (4) which is completely enclosed by the at least one heat conduction layer (3), wherein air-filled cavities are present between metal fibers (5) of the metal fiber composite (4) and the metallic heat conduction layer (3) is formed in the form of a metal foil (8) which has a perforation (9) or as a metal mesh (13), wherein a mesh size of the metal mesh (13) is smaller than a cross-sectional area and / or a minimum length of the intact and / or defective metal fibers (5) present in the metal fiber composite (4).

Description

[0001] The invention relates to a heat conduction arrangement with a heat conduction core and at least one metallic heat conduction layer adjacent to this heat conduction core. The heat conduction core consists of a metal fiber composite on which the heat conduction layer is applied. Air-filled cavities are present between the metal fibers of the metal fiber composite, and the metallic heat conduction layer is in the form of a metal foil. Furthermore, the invention relates to a battery arrangement with a battery and a cooling device, wherein the battery comprises at least one battery cell and a housing on which the cooling device is arranged.

[0002] With the rise of electromobility, there is a steadily increasing demand for high-performance energy storage systems, particularly in the automotive industry. These energy storage systems take the form of batteries, which provide the energy necessary to power electric motors. Due to the power required to propel a vehicle, the current flowing through the stator windings of these motors is high enough to cause significant heating. This current flow not only heats up the electric motor itself, but also the batteries from which the necessary current is drawn. To prevent thermal damage to the batteries, cooling systems can be used, which are integrated into the battery casing.

[0003] Because the battery housings inherently exhibit high surface tolerances due to their manufacturing process, the contact area between the battery housing and the cooling system is significantly smaller than the actual potential contact area between the two. This is disadvantageous in two ways: firstly, the effective contact area for heat conduction is reduced, and secondly, heat-insulating air pockets are present in non-contacting areas, i.e., in the resulting cavities between the battery housing and the cooling system. Such cavities can also be a result of the design. The overall consequence is a significant reduction in heat flow between the battery and the cooling system.

[0004] The same applies to the internal structure of a battery. In particular, high manufacturing tolerances are to be expected between the battery's cell modules and the battery housing. For this reason, a gap is usually incorporated into the design, as compensation is necessary in any case.

[0005] To increase heat conduction between the cell module and the battery housing, as well as between the battery housing and the cooling system, it is possible to introduce heat-conducting materials, for example in the form of thermal pads, between the contact surfaces.

[0006] These materials are generally based on metal oxides embedded in elastomers and, on average, exhibit only ten percent of the thermal conductivity of the embedded metal oxide. The metal oxides themselves, however, possess a maximum thermal conductivity of twenty percent of that of the underlying metal oxide. Furthermore, the already low thermal conductivity decreases dramatically with increasing material thickness.

[0007] US patent 2009 / 0117345A1 discloses a thermal interface material composite consisting of an elastomer-based thermal interface material or a phase-change material and at least one additional separating layer made of a metal or polymer. Furthermore, additional layers, in particular release papers or transfer films, can be included in the thermal interface material composite for the application or insertion of the material between a heat-generating component and a heat-dissipating component. These release papers or transfer films are siliconized, with the applied silicon serving as a separating layer. The release papers or transfer films are removed during or after the application of the thermal interface material composite. The thicknesses of the individual layers are in the range of a few micrometers, and in some cases, only in the range of nanometers.

[0008] Such complex material combinations can therefore only compensate for very small manufacturing tolerances. Tolerances down to the range of a few millimeters cannot be compensated for to a disadvantageous degree.

[0009] Furthermore, DE 10 2009 052 508 A1 discloses a heat conduction arrangement with a heat-conducting core and at least one metallic heat-conducting layer adjacent to this core. The heat-conducting core consists of a metal fiber composite onto which the heat-conducting layer is applied. Air-filled cavities exist between the metal fibers of the metal fiber composite, and the metallic heat-conducting layer is in the form of a metal foil.

[0010] JP 2014 - 212 182 A and JP 2003 - 332 505 A also show heat-conducting arrangements with metal fiber composites, but in this case, there are no air-filled cavities between the metal fibers of the metal fiber composite. Instead, the metal fiber composites are embedded in thermally conductive filler materials.

[0011] Against this background, the invention aims to design a heat conduction arrangement of the type mentioned above in such a way that it enables compensation for distances that are significantly greater than those described in the prior art. Furthermore, the invention aims to provide a battery arrangement of the type mentioned above with improved cooling.

[0012] The first problem is solved with a heat conduction arrangement according to the features of claim 1. The dependent claims relate to particularly advantageous further developments of the invention.

[0013] According to the invention, a heat conduction arrangement is provided with a heat conduction core and at least one metallic heat conduction layer adjacent to this heat conduction core. The heat conduction core consists of a metal fiber composite, which is completely enclosed by the at least one heat conduction layer, thus the metal fiber composite is virtually embedded in the at least one heat conduction layer.

[0014] Such a thermally conductive arrangement combines several advantages. Firstly, it allows for the bridging of both small distances between a heat source and a heat sink, ranging from 0.1 mm to 0.5 mm, and larger distances, ranging from 0.5 mm to 5 mm, and particularly up to 2 mm, with high thermal conductivity. This is due to the high flexibility, i.e., the pronounced elastic properties in the form of a high modulus of elasticity and a high yield strength of the metal fiber composite, combined with its high compressibility.

[0015] The compressibility is largely due to the air-filled cavities present between the metal fibers of the metal fiber composite according to the invention, the volume of which is minimized when the metal fiber composite is compressed. Furthermore, the encasing of the metal fiber composite with the heat-conducting layer provides a large contact area with the heat sink and the heat source. At the same time, the heat-conducting layer offers protection against any metal fibers that might protrude from the metal fiber composite, thus reducing the risk of defects. Despite the air-filled cavities between the metal fibers of the metal fiber composite, the use of metals with correspondingly high thermal conductivity coefficients allows for an overall thermal conductivity of the heat-conducting arrangement in the range of 10 watts per kelvin per meter to 20 watts per kelvin per meter, or even up to 25 watts per kelvin per meter.This overall thermal conductivity would therefore be at least twice as high as that of thermally conductive materials based on metal oxide particles embedded in elastomers. Furthermore, only a slight fluctuation in the overall thermal conductivity of the heat-conducting arrangement would be expected when it is compressed, in the range of one watt per Kelvin per meter to two watts per Kelvin per meter. This should also be the case if the thickness of the heat-conducting arrangement varies across its surface area due to its adaptation to the surface contours of the heat source and heat sink.

[0016] Regarding the thermal conductivity layers, it is conceivable that only one thermal conductivity layer is provided, which, for example, overlaps the metal fiber composite at least partially in the edge regions, either facing towards or away from it. Alternatively, two thermal conductivity layers could be provided, completely enclosing the metal fiber composite and overlapping at least partially in their edge region. This overlapping edge region could also be used to bond the thermal conductivity layers together, for example, by means of a material bond. Any protrusion of the thermal conductivity layers beyond the metal fiber composite can vary depending on the requirements. An unbonded portion of the edge region could serve for pressure equalization during the compression of the thermal conductivity arrangement.

[0017] Furthermore, due to the reduced manufacturing effort and the materials used in the heat conduction arrangement according to the invention, there is a significant cost saving compared to heat conduction materials which are based on metal oxide particles embedded in elastomers.

[0018] According to the invention, the metallic heat-conducting layer is further provided to be in the form of a perforated metal foil or a metal mesh. The mesh size of the metal mesh is smaller than the cross-sectional area and / or the minimum length of the intact and / or defective metal fibers present in the metal fiber composite.

[0019] The metal foil could have a thickness in the range of 0.1 mm to 0.5 mm, and particularly a thickness of 0.2 mm. Suitable materials for this metal foil include, for example, aluminum and copper, but also steels and / or aluminum-coated steels. Using the metal foil as a heat-conducting layer allows for excellent conformability to the cavity between the heat source and heat sink, which the heat-conducting arrangement is intended to fill, while simultaneously providing a large contact area. Furthermore, due to its continuous, closed-surface structure, the metal foil is particularly well-suited for enclosing the metal fiber composite and preventing fiber escape.

[0020] Based on the perforation of the metal foil, it would also be possible for the air located in the cavities between the metal fibers of the metal fiber composite to escape from the heat-conducting arrangement during compression. This would allow for a complete seal of the heat-conducting layer, which is designed as a metal foil, at its edges. The perforations should be in the form of holes oriented in the direction of the thickness of the metal foil and with a diameter of less than one millimeter, ideally less than 0.1 millimeters. The holes could be produced by microneedling, etching, or laser processing.

[0021] By using a metal mesh, an airflow between the cavities of the metal fiber composite and the surrounding environment would be possible during compression of the heat conduction arrangement. Due to its mesh structure, perforation of the metal mesh would not be necessary. However, the mesh size of the metal mesh should be so small that no metal fibers from the metal fiber composite can escape from the heat conduction arrangement. This applies both to fibers inherent in the metal fiber composite and to metal fibers that have escaped due to overload, e.g., from breakage. For this reason, a mesh size of less than 1 millimeter, and preferably less than 0.1 millimeter, should be used.

[0022] In a particularly advantageous embodiment of the invention, the metal fiber composite is formed as a metal fleece with disordered metal fibers of the same and / or different fiber lengths. By means of a disordered arrangement of the metal fibers in the metal fiber composite formed as a metal fleece, isotropic mechanical properties, such as elasticity and / or stiffness, can be achieved in the spatial directions of the metal fiber composite.

[0023] A further advantageous embodiment of the invention is also characterized in that the metal fiber composite is formed in the form of a metal woven, knitted, or crocheted fabric with ordered fibers of the same and / or different fiber lengths. By ordering the metal fibers in the metal fiber composite formed as a metal nonwoven, anisotropic mechanical properties, such as elasticity and / or stiffness, can be achieved in the spatial directions of the metal fiber composite, in contrast to an ordered arrangement.

[0024] In both cases, i.e., whether the metal fibers are arranged in an ordered or disordered manner within the metal fiber composite formed as a metal fleece, the mechanical properties, such as elasticity and / or stiffness, the geometric properties of the metal fibers, such as their length and cross-section, as well as their number in the metal fleece and thus the metal fiber density and the material from which the metal fibers of the metal fleece are made, can be influenced. Suitable materials include steels, aluminum-coated steels, but also copper and aluminum, or even mixtures thereof.

[0025] Furthermore, in cases of ordered or disordered arrangement of the metal fibers in the metal fiber composite, it would be conceivable to transform them into a desired geometric shape, which could result, for example, from the positioning of the heat-conducting arrangement. This could be achieved, among other things, by pressing the metal fiber composite. Depending on the desired mechanical properties, it would be advantageous to choose an ordered or disordered arrangement of the metal fibers in order to achieve direction-dependent or direction-independent properties of the metal fiber composite and thus of the heat-conducting arrangement.

[0026] Furthermore, if the metallic heat conduction layer, designed as a metal foil, has an embossing, this can be described as advantageous in that different strength properties, such as the level of tensile strength and stiffness, can be achieved in the metal foil due to and depending on the embossing.

[0027] Furthermore, it proves very practical if the metallic heat-conducting layer has an adhesion promoter layer on its side facing the metal fiber composite, via which the heat-conducting layer can be bonded to the metal fiber composite in a material-bonded manner. This would advantageously lead to a further increase in the overall thermal conductivity of the heat-conducting arrangement, since a loose contact and thus also a change in the contact points between the heat-conducting layer and the metal fiber composite would be prevented.

[0028] Furthermore, if the adhesion promoter layer consists of a hard- or soft-solderable metal and / or a metal alloy or a thermally conductive adhesive, it offers possibilities for generating a metallurgical bond between the thermal interface material and the metal fiber composite, requiring only a thin layer thickness of the adhesion promoter layer in the range of 50 to 100 micrometers. This simultaneously guarantees a metallurgical bond between the metal fiber composite and the thermal interface material and a high thermal conductivity coefficient. For this purpose, the adhesion promoter layer could consist of tin or a tin alloy with copper and / or silver components. In an embodiment of the adhesion promoter layer as a thermally conductive adhesive, it could be epoxy- or silicone-based, with ceramic or metallic fillers incorporated into the epoxy resin or silicone.

[0029] The heat treatment necessary when using a hard- or soft-solderable metal as an adhesion promoter layer for the material-bonded connection of the heat conducting layer and the metal fiber composite could take place during or after the arrangement of the heat conducting layer around the metal fiber composite.

[0030] A particularly promising embodiment of the heat conduction arrangement according to the invention is also achieved by providing the heat conduction arrangement with an electrical insulating layer and / or an electrical insulating layer on the side of the heat conduction layer facing away from the metal fiber composite. By means of the insulating layer and / or the insulating layer, the conduction of electric current through the heat conduction arrangement could be prevented in electrically critical applications where contact between the heat source and heat sink with an electrically conductive heat conduction arrangement is undesirable. The electrical insulating layer could consist of an electrically non-conductive film that encloses the heat conduction arrangement. The film could either be in loose contact with the heat conduction layer or be rolled or laminated onto it.In the case of the insulating layer, it is conceivable to apply it to the thermal conductivity layer using known coating methods such as dip or spray coating, vapor deposition, or even cathodic sputtering. It should be noted that any perforations in the thermal conductivity layer must be continued into the insulating layer and / or insulating layer.

[0031] The second problem is also solved with a battery arrangement according to the features of claim 8.

[0032] Thus, according to the invention, a battery arrangement is provided with a battery comprising at least one battery cell and a housing, and a cooling device arranged on the battery housing. Furthermore, at least one previously described heat conduction arrangement is arranged between the battery cell and the housing and / or between the battery housing and the cooling device. In particular, the battery should be designed as a rechargeable accumulator.Due to the arrangement of the heat transfer arrangement or multiple heat transfer arrangements between the at least one battery cell and the housing, or between the housing and the cooling device, an increased heat flow would occur between the battery cell and the housing and / or between the housing and the cooling device compared to a design without a heat transfer arrangement, as well as compared to the arrangement of heat-conducting materials between the battery cell and the housing and / or between the housing and the cooling device, which are based on metal oxide particles embedded in elastomers. This would result in a lower temperature increase of the battery during operation. Thus, for example, the battery's lifespan could be increased and / or a higher current draw could be achieved.

[0033] The invention allows for numerous embodiments. To further illustrate its basic principle, some of these are shown in the drawing and described below. The drawing shows in Fig. 1 a basic structure of a heat conduction arrangement according to the invention; Fig. 2a, Fig. 2b, Fig. 2c Cross-sections of heat conduction arrangements according to the invention; Fig. 3 a heat conduction arrangement with metal mesh; Fig. 4 a battery arrangement according to the invention.

[0034] Fig. Figure 1 shows the basic structure of a heat conduction arrangement 1 according to the invention in an exploded view. The heat conduction arrangement 1 shows the heat conduction core 2, which here consists of the metal fiber composite 4. The heat conduction arrangement 1 also has the metallic heat conduction layer 3 adjacent to the heat conduction core 2, which completely encloses the metal fiber composite 4. It should be further noted that the metallic heat conduction layer 3 is designed in the form of the metal foil 8, which is provided with the perforation 9. The metallic heat conduction layer 3, designed as a metal foil 8, also shows the adhesion promoter layer 10 on its side facing the metal fiber composite 4, via which the heat conduction layer 3 is bonded to the metal fiber composite 4. The perforation 9 is also shown in the adhesion promoter layer 10, as it continues into the adhesion promoter layer 10.

[0035] Fig. 2a, Fig. 2b and Fig. Figure 2c illustrates cross-sections of heat conduction arrangements 1 according to the invention, wherein the in Fig. 2a as well as in Fig. The representations shown in 2c include heat conduction arrangements 1 whose metal fiber composite 4 is in the form of the metal fleece 7 with disordered metal fibers 5 of different fiber lengths. In contrast, the one shown in Fig. Figure 2b shows a heat conduction arrangement 1 via a metal fiber composite 4, which is formed as a metal fabric 6 with ordered metal fibers 5 of the same and different fiber lengths. The metal fiber composite 4, designed as a metal fleece 7 or as a metal fabric 6, is in turn enclosed by the heat conduction layer 3 or layers 3, which are designed as a metal foil 8. This layer again has the adhesion promoter layer 10 on its side facing the metal fiber composite 4, via which the heat conduction layer 3 is bonded to the metal fiber composite 4. Fig. 2a, Fig. 2b and Fig. Figure 2c also shows a different number of heat conduction layers 3. Fig. 2a and Fig. Figure 2b shows heat conduction arrangements 1 with two heat conduction layers 3 bonded together via the adhesion promoter layer 10. The heat conduction layers 3 enclose the metal fiber composite 4 on all sides, overlapping in their edge region 11, facing away from the metal fiber composite 4. The projection 12 of the heat conduction layers 3 over the metal fiber composite 4 differs in the Fig. 2a and Fig. 2b differ in that the excess 12 of the in Fig. 2a shows that the heat conduction layers 3 are more pronounced than the protrusion 12 of the in Fig. 2b shown heat conduction layers 3. The in Fig. In contrast, the heat conduction arrangement 1 shown in 2c only shows one heat conduction layer 3. This heat conduction layer 3 overlaps, unlike the Fig. 2a and Fig. 2b, facing the metal fiber composite 4, in the edge area 11 of the metal fiber composite 4.

[0036] In Fig. Figure 3 shows a heat conduction arrangement 1, whose metallic heat conduction layers 3 are formed in the form of a metal mesh 13. The metal meshes 13 enclose the metal fiber composite 4, which here is formed in the form of a metal fleece 7 with disordered metal fibers 5. Furthermore, the metal meshes 13 are interconnected in their edge region 11 facing away from the metal fiber composite 4.

[0037] Fig.Figure 4 shows a schematic representation of a battery arrangement 20 according to the invention. The battery arrangement 20 comprises the battery 21 and the cooling device 24. The battery 21 itself also has four battery cells 22 and the housing 23, on which the cooling device 24 is arranged. In addition, a heat conduction arrangement 1 is arranged between the battery cells 22, between the battery cell 22 facing the cooling device 24 and the housing 23, and between the housing 23 of the battery 21 and the cooling device 24. Reference symbol list 1 Heat conduction arrangement 2 thermal conductivity core 3 Heat conduction layer 4 Metal fiber composite 5 metal fibers 6 Metal woven, knitted or crocheted fabrics 7 Metal fleece 8 metal foil 9-hole 10 Liability mediator layer 11 Edge area 12 Overhang 13 Metal mesh 20 Battery arrangement 21 Battery 22 battery cells 23 cases 24 Cooling device

Claims

[1] Heat conduction arrangement (1) with a heat conduction core (2) and at least one metallic heat conduction layer (3) adjacent to this heat conduction core (2), wherein the heat conduction core (2) consists of a metal fiber composite (4) which is completely enclosed by the at least one heat conduction layer (3), wherein air-filled cavities are present between metal fibers (5) of the metal fiber composite (4) and the metallic heat conduction layer (3) is formed in the form of a metal foil (8) which has a perforation (9) or as a metal mesh (13), wherein a mesh size of the metal mesh (13) is smaller than a cross-sectional area and / or a minimum length of the intact and / or defective metal fibers (5) present in the metal fiber composite (4). [2] Heat conduction arrangement (1) according to claim 1, characterized by , that the metal fiber composite (4) is in the form of a metal fleece (7) with disordered metal fibers (5) with the same and / or different fiber lengths. [3] Heat conduction arrangement (1) according to claim 1, characterized by , that the metal fiber composite (4) is formed in the form of a metal woven, knitted or crocheted fabric (6) with ordered metal fibers (5) of the same and / or different fiber lengths. [4] Heat conduction arrangement (1) according to at least one of the preceding claims, characterized by , that the metallic heat conducting layer (3) designed as a metal foil (8) has an embossing. [5] Heat conduction arrangement (1) according to at least one of the preceding claims, characterized by , that the metallic heat conducting layer (3) has an adhesion promoter layer (10) on its side facing the metal fiber composite (4), via which the heat conducting layer (3) can be bonded to the metal fiber composite (4). [6] Heat conduction arrangement (1) according to the preceding claim, characterized by, that the adhesion promoter layer (10) consists of a hard- or soft-solderable metal and / or a metal alloy or a thermally conductive adhesive. [7] Heat conduction arrangement (1) according to at least one of the preceding claims, characterized by , that the heat conduction arrangement (1) has an electrical insulation layer and / or an electrical insulation layer on the side of the heat conduction layer (3) facing away from the metal fiber composite (4). [8] Battery arrangement (20) comprising a battery (21), wherein the battery (21) comprises at least one battery cell (22) and a housing (23), and a cooling device (24) arranged on the housing (23) of the battery (21), characterized by , that at least one heat conduction arrangement (1) according to at least one of the preceding claims is arranged between the battery cell (22) and the housing (23) and / or between the housing (23) of the battery (21) and the cooling device (24).

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