Method for thermally bonding a battery module to a housing component, battery arrangement and motor vehicle

Abstract

The invention relates to a method for thermally bonding at least one battery module (12) to a housing component (16) using a curable thermal interface material (20), wherein, while the thermal interface material (20) is in a viscous state (Z), the at least one battery module (12), the housing component (16), and the thermal interface material (20) are arranged relative to each other such that the thermal interface material (20) is located between the housing component (16) and the battery module (12). The thermal interface material (20) is electrically conductive, and after arrangement, an electrical voltage (U) is applied to the thermal interface material (20) to generate an electric current (I) through it.

Description

[0001] The invention relates to a method for thermally bonding at least one battery module to a housing component using a curable thermal interface material. While the thermal interface material is in a viscous state, the at least one battery module, the housing component, and the thermal interface material are arranged relative to one another such that the thermal interface material is located between the housing component and the battery module. Furthermore, the invention also relates to a battery assembly and a motor vehicle.

[0002] In high-voltage batteries of electric vehicles, heat is generated during rapid charging and when power is drawn, which must be dissipated as effectively as possible to increase service life. For this purpose, the battery modules of such a high-voltage battery can be cooled using a cooling system. To connect the battery modules to such a cooling system as efficiently as possible, a thermal interface material (TIM), for example in the form of a gap filler, is often used between the battery modules and the cooling system. Such gap fillers are often two-component reactive materials that require several hours after mixing to achieve their final properties. Another subgroup of thermal interface materials are thermally conductive adhesives. These can cure more quickly than typical gap fillers.Nevertheless, such adhesives must not cure too quickly to prevent them from being partially cured or cross-linked before the joining partners, namely the at least one battery module and the housing component, have even been joined. In any case, the fastest possible but targeted curing of such a thermal interface material would be desirable.

[0003] DE 10 2017 100 030 A1 describes a device for providing a uniform distribution of waste heat in a battery pack. The device comprises the battery pack, a cold plate, a coolant reservoir, a support structure between the battery pack and the coolant reservoir, and a deformable thermally conductive paste for filling the space between cells of the battery pack and the coolant reservoir to provide thermal contact between the cells and the coolant reservoir to distribute the waste heat. The thermally conductive paste can be a liquid polymer or liquid gel. The thermally conductive paste can be crosslinked, and the crosslinking can be performed thermally or photochemically. Other crosslinking methods include ultraviolet and laser crosslinking.

[0004] The object of the present invention is to provide a method, a battery arrangement and a motor vehicle which enable the curing of a thermal interface material arranged between a battery module and a housing component to be as fast as possible and controlled in terms of time as precisely as possible.

[0005] This object is achieved by a method, a battery arrangement, and a motor vehicle having the features according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figure.

[0006] In a method according to the invention for thermally bonding at least one battery module to a housing component using a curable thermal interface material, the at least one battery module, the housing component, and the thermal interface material are arranged relative to one another while the thermal interface material is in a viscous state such that the thermal interface material is located between the housing component and the battery module. The thermal interface material is electrically conductive, and after being arranged, an electrical voltage is applied to the thermal interface material to generate an electrical current through the thermal interface material.

[0007] This has the major advantage that the heat loss resulting from the current flow through the thermal interface material and caused by the ohmic resistance of the thermal interface material can be used to accelerate the curing of the thermal interface material. The acceleration of the curing process can also be controlled in a targeted manner by applying the voltage. In particular, the point in time at which this acceleration of curing should begin through the application of the electrical voltage can be specifically controlled by choosing the point in time at which the voltage is applied or activated. This can also prevent the thermal interface material from curing too prematurely. Another major advantage is that the heat causing the acceleration of curing is generated internally within the material and does not have to be introduced into the thermal interface material from outside.This allows the generated heat to be used much more efficiently, reducing heat loss. The heat is generated precisely where it's needed, namely within the thermal interface material. This advantageously eliminates the need for additional external heat to accelerate the curing process.

[0008] The battery module can have one or more battery cells. Such a battery cell can, for example, be designed as a lithium-ion cell. The housing component can be a component of a battery housing. Optionally, several battery modules can be accommodated in such a battery housing. The housing component can, for example, represent a housing base or a housing cover of such a battery housing, or any side wall or partition between two receiving areas within the battery housing for accommodating respective battery modules. The housing component can also be simultaneously designed as a cooling device. This can, for example, comprise cooling channels through which a coolant can flow. The housing component can also be indirectly connected to an additional cooling device. As a result, the battery module can advantageously be cooled via the housing component.The thermal interface material located between the battery module and the housing component ensures efficient heat dissipation from the battery module to the housing component during operation of the battery module.

[0009] If the thermal interface material is arranged between the battery module and the housing component, the thermal interface material preferably contacts the battery module on the one hand and the housing component on the other. The thermal interface material can provide a thermal interface material layer between the battery module and the housing component. In particular, the surface of the housing component which faces the battery module and on which the thermal interface material is arranged can be substantially flat or planar. Furthermore, the arrangement comprising battery module, thermal interface material and housing component is designed such that the battery module is electrically insulated from the housing component. Therefore, although the thermal interface material is electrically conductive, there is no electrically conductive connection between the battery module and the housing component.The battery module can, for example, be formed or provided with an electrically insulating protective film on a side facing the housing component, which, when properly arranged, contacts the thermal interface material. Additionally or alternatively, the surface of the housing component facing the battery module can be electrically insulating, for example, with an electrically insulating coating or film or similar.

[0010] The application of electrical voltage to the thermal interface material can be switched on and off at will. This means that once the thermal interface material has sufficiently cured according to at least one predetermined criterion, the applied voltage can be deactivated again accordingly. An electrical voltage is therefore only applied to the thermal interface material for the purpose of accelerating its curing or to start or trigger the curing process. With some thermal interface materials, e.g. some polymerization adhesives, a "kick-start" using energy, e.g. external energy, is sufficient to initiate the curing process. This starting energy can also be provided by the current flow induced by the voltage, whereby the voltage can also be applied for a relatively short time in order to trigger a corresponding current pulse.

[0011] The electrical voltage can generally be applied, for example, for a predetermined period of time. Furthermore, depending on the selected level of the electrical voltage, the rate of accelerated curing of the thermal interface material can be determined and controlled. This enables rapid and defined curing. The side of the battery module facing the housing component, which represents an outer side of the battery module, can in particular be provided by the sides of the cells contained in the battery module.

[0012] According to a further very advantageous embodiment of the invention, a thermally conductive adhesive is used as the thermal interface material. The use of a thermally conductive adhesive has the great advantage that, once it has cured, even mechanical loads can be transmitted via this thermally conductive adhesive. In other words, forces can then be transmitted between the module and the housing component via this thermally conductive adhesive. This can also be advantageously utilized during production, because if partially defined strengths are already achieved during production, the housing component or the battery module assembly part can be moved or rotated upside down.Using the above-described process for accelerated curing of the thermally conductive adhesive, the adhesive can at least partially cure shortly after the material has been applied to the housing component, for example, in the battery tray, and the battery module has been joined, thus absorbing mechanical loads and providing a certain degree of handling strength. Such a thermally conductive adhesive can, for example, be provided on a polymer basis. This has the significant advantage that the curing of reactive polymers in particular can be greatly accelerated through the introduction of heat. As described, the introduction of heat results from the application of voltage to the thermal interface material, which in turn causes a current to flow through the thermal interface material, which in turn generates heat within the thermal interface material itself.

[0013] In a further advantageous embodiment of the invention, the thermal interface material comprises an electrically conductive filler, in particular in the form of electrically conductive particles, which is embedded in an electrically non-conductive matrix, for example a polymer matrix, of the thermal interface material. By embedding an electrically conductive filler in a matrix, an electrically conductive thermally conductive adhesive or, in general, an electrically conductive thermal interface material can be easily provided. Furthermore, electrically conductive fillers, in particular electrically conductive particles such as aluminum, have the advantage of also being very thermally conductive. This allows the thermal interface material to be simultaneously designed with very good thermal conduction properties.It can also be provided that the thermal interface material comprises not only electrically conductive fillers, but also, for example, various fillers, only some of which are electrically conductive. However, it is particularly preferred that the thermal interface material exclusively comprises electrically conductive fillers embedded in the electrically non-conductive matrix. This makes it particularly easy to ensure that when a voltage is applied to the thermal interface material, an electric current also flows through the thermal interface material.

[0014] In a further advantageous embodiment of the invention, at least 50 percent, in particular at least 60 percent, preferably at least 70 percent of the volume of the thermal interface material consists of the filler, particularly under standard conditions or normal conditions, e.g., at a temperature of 0°C and an ambient pressure of 1013.25 bar. These percentages can refer in particular to the viscous state of the thermal interface material or to the cured state.

[0015] At least a large portion of the volume of the thermal interface material consists of the electrically conductive filler. The filler content is preferably between 60 percent and 90 percent, particularly preferably in the order of 80 percent. This ensures sufficiently good electrical conductivity and provides very good thermal properties.

[0016] In a further advantageous embodiment of the invention, the voltage is applied to the thermal interface material by means of at least one pair of electrodes. Such an electrode pair comprises, for example, a positive and a negative electrode. Each electrode is thus assigned a different electrical potential. The electrodes can be, for example, elongated electrodes or point electrodes. It is particularly advantageous if the electrodes are arranged on the thermal interface material in an edge region of the battery module.

[0017] It can also be provided that the voltage is applied to different areas of the thermal interface material using several pairs of electrodes. It would also be conceivable, for example, to provide a single electrode assigned to a first potential and several second electrodes, each assigned to the same second potential or to different second potentials. In principle, the application of the voltage does not necessarily have to result in a homogeneous electrical current flow through the entire surface of the thermal interface material. It is also conceivable, for example, that such a current flow occurs, at least in an amplified manner, only in individual areas of the thermal interface material, which then, for example, harden faster than other areas of the thermal interface material.Local curing of the thermal interface material, for example, enables sufficient strength and stability of the battery module relative to the housing component, allowing subsequent manufacturing and assembly steps to be carried out without having to wait until the entire thermal interface material has fully cured. Thus, the voltage can be applied to the thermal interface material in such a way that different areas of the thermal interface material cure at different rates, or accelerated curing of the thermal interface material occurs only in one or more sub-areas of the thermal interface material.

[0018] The battery module can, as already mentioned above, comprise, for example, a plurality of battery cells. These can be arranged next to one another in a stacking direction. The battery module can, for example, have a length that is defined in the stacking direction and a width perpendicular to the stacking direction. The electrodes of an electrode pair can, for example, be arranged on opposite sides of the battery module relative to the length of the battery module or also relative to the width of the battery module. Several individual electrodes can also be provided on one side of the battery module in the length direction and / or in the width direction. However, elongated electrodes can also be provided which extend over a large part or the entire side of the battery module, for example in the length direction or in the width direction.

[0019] In a further advantageous embodiment of the invention, the application of the voltage is terminated and at least one electrode of the at least one electrode pair is removed from the thermal interface material arranged between the at least one battery module and the housing component. The electrodes can generally be arranged on the thermal interface material solely for the purpose of applying the voltage and can be removed from it again after the thermal interface material has sufficiently cured. For example, the electrodes can be provided as part of or together with a gripper that places the battery module onto the housing component wetted with the thermal interface material. However, it is also conceivable for one or more electrodes to remain in this component arrangement even after the voltage has been applied, i.e., when voltage is no longer present. It is also conceivable to use parts of the housing as such an electrode.For example, a part of the housing component itself can also function as an electrode.

[0020] Furthermore, the invention also relates to a battery assembly for a motor vehicle, which was manufactured using a method according to the invention or one of its embodiments. The battery assembly can thus comprise the battery module, the housing component, and the thermal interface material arranged between the housing component and the battery module.

[0021] The advantages described for the method according to the invention and its embodiments apply equally to the battery arrangement according to the invention.

[0022] In a further advantageous embodiment of the invention, the battery arrangement is designed as a high-voltage battery. For this purpose, the battery arrangement can in particular have a plurality of battery modules. Each of these plurality of battery modules can in turn comprise a plurality of battery cells. The plurality of battery modules can be arranged on a same housing component, for example in a housing tray, and thermally connected to it via the thermal interface material. The battery modules can be connected to the housing component simultaneously or sequentially via a respective thermal interface material. The procedure for this connection can be as already described above for an individual battery module.

[0023] Furthermore, the invention also relates to a motor vehicle with a battery arrangement according to the invention or one of its embodiments.

[0024] The invention also includes further developments of the battery arrangement according to the invention that have features already described in connection with the further developments of the method according to the invention. For this reason, the corresponding further developments of the battery arrangement according to the invention are not described again here.

[0025] The motor vehicle according to the invention is preferably designed as a motor vehicle, in particular as a passenger car or truck, or as a passenger bus or motorcycle.

[0026] The invention also encompasses combinations of the features of the described embodiments. The invention therefore also encompasses implementations that each comprise a combination of the features of several of the described embodiments, unless the embodiments are described as mutually exclusive.

[0027] Exemplary embodiments of the invention are described below. The exemplary embodiments explained below are preferred embodiments of the invention. In the exemplary embodiments, the described components of the embodiments each represent individual features of the invention that can be considered independently of one another, each of which also develops the invention independently of one another. Therefore, the disclosure is intended to encompass combinations of the features of the embodiments other than those shown. Furthermore, the described embodiments can also be supplemented by further features of the invention already described.

[0028] The only figure shows a schematic representation of a battery arrangement during production according to an embodiment of the invention.

[0029] The figure shows a schematic representation of a battery arrangement during production according to an exemplary embodiment of the invention. The battery arrangement 10 comprises a battery module 12, which can have, for example, a plurality of battery cells 14, a housing component 16, which can be formed, for example, as part of a battery tray 18, and a thermal interface material 20. During production of the battery arrangement 10, the battery module 12, the housing component 16 and the thermal interface material 20 are arranged relative to one another such that the thermal interface material 20 is located between the battery module 12 and the housing component 16 and, for example, contacts a first contact side 12a of the battery module and a second contact side 16a of the housing component. The first contact side 12a of the battery module 12 faces the second contact side 16a of the housing component.

[0030] The thermal interface material 20 is preferably formed as a thermally conductive adhesive 22. This adhesive can, for example, comprise an electrically non-conductive matrix 24 and a filler 26 that is electrically conductive and, in this case, is provided in the form of electrically conductive particles 28. For reasons of clarity, only some of the particles 28 are provided with a reference symbol.

[0031] If the components of the battery assembly 20 are arranged relative to one another as intended, this is done, for example, by first applying the thermal interface material 20 in a viscous state Z to the second contact side 16a of the housing component 16, and then placing the battery module 12 with its first contact side 12a thereon, whereby, for example, the thermal interface material 20 is initially pressed into the surface. The layer thickness of this material layer of the thermal interface material 20 in the z-direction shown here is a maximum of a few millimeters. The layer thickness can be, for example, less than 2 mm or less than 1 mm.

[0032] If the aforementioned components are now arranged relative to one another as intended, as shown in the figure, a targeted, accelerated curing of the thermally conductive adhesive 22 is used. This is achieved by applying a voltage U to the thermal interface material 30. For this purpose, two electrodes 26a, 26b can be provided, forming an electrode pair 26. Because the thermal interface material 20 comprises electrically conductive particles 28, the applied voltage U results in a current flow I through the thermal interface material 20, which is illustrated here by way of example by an arrow.

[0033] In the thermal interface material 20, the proportion of fillers 26, in particular thermally conductive fillers 26, is preferably significantly higher than the polymer content that provides the matrix 24. The volume ratio of filler 26 to matrix 24 is preferably approximately 80 to 20. In addition to electrically insulating fillers, such as ceramics and aluminum hydroxide, there are also electrically conductive fillers 26, such as aluminum or other metals, which are preferably used here. If, after joining the battery module 12 into the tub 18, a voltage U is applied to the electrically conductive thermal interface material 20 as described, the current I jumps from filler particle 28 to filler particle 28, and the internal resistance of the fillers can be used to accelerate the curing process, because the current flow I generates corresponding heat in these fillers 26, in particular according to Joule's first law: Qw=I2⋅R⋅t=U2R⋅t.

[0034] Qw denotes the heat energy, I the electric current, R the electrical resistance of the fillers 26, t the time for which the current flow lasts, and U the applied voltage.

[0035] The heat Qw generated by the current flow I then advantageously leads to an accelerated chemical reaction of the curing process of the thermal interface material 20. The speed of the reaction can be accelerated by the level of the voltage U or the current I. Once the thermal interface material 20 has sufficiently cured, the voltage U can be switched off and, optionally, the electrodes 26a, 26b can also be removed. The curing of the thermal interface material 20 upon application of the voltage U does not necessarily have to occur homogeneously across the surface of the thermal interface material 20, but can also occur only in certain areas. This can already provide sufficient stability of the connection between module 12 and tub 18 in order to be able to carry out subsequent manufacturing and process steps.By accelerating the curing process, the thermal interface material 20 can now advantageously absorb mechanical loads and provide a certain degree of handling strength shortly after the thermal interface material 20 has been introduced into the tray 18 and the battery module 12 has been joined. Furthermore, this accelerated curing reaction can be specifically activated once the two joining partners, i.e., the battery module 12 and the housing component 16, have been introduced, i.e., arranged relative to one another as intended. The curing of the reactive polymers that provide the matrix 24 can be greatly accelerated by this heat input or heat generation within the thermal interface material 20.By applying the voltage U, it is now advantageously possible to generate this heat inside the thermal interface material 20 by using the fillers 26 of the thermal interface material 20 as a resistor.

[0036] Overall, the examples demonstrate how the invention can provide a method for rapidly curing a thermal interface material. The advantage of this concept is that no additional heat, such as infrared heat, is required. The fillers already contained in the thermal interface material can be used to advantage. Furthermore, the process can be precisely accelerated when strength buildup is required. 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] DE 10 2017 100 030 A1

[0003]

Claims

[1] Method for thermally connecting at least one battery module (12) to a housing component (16) by means of a curable thermal interface material (20), comprising the step: - while the thermal interface material (20) is in a viscous state (Z), arranging the at least one battery module (12), the housing component (16) and the thermal interface material (20) relative to one another such that the thermal interface material (20) is located between the housing component (16) and the battery module (12), characterized by , that - the thermal interface material (20) is electrically conductive and - after arranging to generate an electrical current (I) through the thermal interface material (20), an electrical voltage (U) is applied to the thermal interface material (20). [2] Method according to claim 1, characterized bythat a thermally conductive adhesive (22) is used as the thermal interface material (20). [3] Method according to one of the preceding claims, characterized by that the thermal interface material (20) comprises an electrically conductive filler (26), in particular electrically conductive particles (28), which is embedded in an electrically non-conductive matrix (24) of the thermal interface material (20). [4] Method according to claim 3, characterized by that at least 50%, in particular at least 60%, preferably at least 70% of the volume of the thermal interface material (20) consists of the filler (26). [5] Method according to one of the preceding claims, characterized by that the voltage (U) is applied to the thermal interface material (20) by means of at least one pair of electrodes (26). [6] Method according to one of the preceding claims, characterized bythat the voltage (U) is applied to different areas of the thermal interface material (20) by means of several pairs of electrodes (26). [7] Method according to one of the preceding claims, characterized by that the application of the voltage (U) is terminated and at least one electrode (26a, 28b) of the at least one electrode pair (26) is removed from the thermal interface material (20) arranged between the at least one battery module (12) and the housing component (16). [8] Battery assembly (10) for a motor vehicle, which was manufactured by means of a method according to one of the preceding claims, wherein the battery assembly (10) comprises the battery module (12), the housing component (16) and the thermal interface material (20) arranged between the housing component (16) and the battery module (12). [9] Battery arrangement (10) according to claim 8, characterized bythat the battery arrangement (10) is designed as a high-voltage battery. [10] Motor vehicle with a battery arrangement (10) according to claim 8 or 9.

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