Method for manufacturing a joining unit, and joining unit, in particular an energy storage unit

Abstract

The invention relates to a method for manufacturing a joining unit (10, 40, 40'), in particular an energy storage unit (30) of an energy storage device or an electrolyzer, wherein a first component (12, 44, 44') is provided, which has a first connection section (20, 44a, 44a') formed from a metallic material, wherein a second component (24, 24a, 24b, 42) is provided, which has a second connection section (24, 24a, 24b, 48) formed from an electrically insulating material, in particular a plastic. The first connection section (20, 44a, 44a') and the second connection section (24, 24a, 24b, 48) are arranged in contact with each other and joined together by means of a thermal joining process, according to which at least the second connection section (24, 24a, 24b, 48) is heated at least locally.

Description

[0001] The invention relates to a method for producing a joining unit, in particular for an energy storage unit of an energy storage device, e.g., for a motor vehicle. A first component is provided that has a first connection section formed from a metallic material, and a second component is provided that has a second connection section formed from an electrically insulating material. Furthermore, the invention also relates to a joining unit, in particular for an energy storage unit of an energy storage device for a motor vehicle.

[0002] Primarily in connection with the construction of energy storage systems for motor vehicles, but also in other applications, processes are used to join different components, especially for joining metallic components on the one hand with electrically insulating components, e.g. plastic components, on the other. In these processes, either a plastic component is attached to the metallic component in an injection molding process, or adhesives and / or sealing materials are used, depending on the application. These adhesives or sealants must then be additionally applied in a separate process step and subsequently cured, for which curing units such as ovens are used in the subsequent process. Overall, such joining processes are very cost-intensive and complex.

[0003] DE 100 25 207 A1 describes a fuel cell formed from a stack of membrane electrode assemblies arranged one behind the other with their flat sides facing one another, each separated from the other by a bipolar plate, with a single pole plate serving as an end plate in front of the first and behind the last membrane electrode assemblies. The stack is traversed by distribution and collection channels for supplying and discharging fuel, oxidant, and coolant to the fuel cell. The membrane electrode assemblies, the bipolar plates, and the end plates are each surrounded by a plastic frame, which can be attached to the individual units or plates by an injection molding process. These plastic frames are sealed together by welding or gluing.

[0004] Furthermore, DE 10 2007 007 986 A1 describes an energy storage device for electrical energy, comprising, among other things, a housing for at least one energy storage cell mounted and secured within the housing, which consists of at least one pair of electrodes enclosed on all sides by a flexible housing. The flexible housing is tightly sealed on at least one side of the energy storage cell by a seam, creating a border adjacent to the pair of electrodes. The energy storage cells are secured in the housing by clamping at least one border between the housing modules. This eliminates the need for the usual folding of the weld seams.

[0005] The object of the present invention is to provide a method and a joining unit, in particular for an energy storage unit, which allow the most efficient production possible.

[0006] This object is achieved by a method and a joining unit according to the respective independent patent claims. Advantageous embodiments of the invention are the subject of the dependent patent claims, the description, and the figures.

[0007] In a method according to the invention for producing a joining unit, in particular an energy storage unit of an energy storage device for a motor vehicle, a first component is provided which has a first connection section formed from a metallic material, and a second component is provided which has a second connection section formed from an electrically insulating material. The first connection section and the second connection section are arranged in contact with one another and joined to one another in a material-locking manner by means of a thermal joining method, according to which at least the second connection section is heated at least locally.

[0008] The invention is based on the finding that it is possible to provide a very stable, robust, and materially bonded connection between a component made of an electrically insulating material, e.g., a plastic component, and a metallic component by at least partially melting the component made of the electrically insulating material. This melting can be achieved by the aforementioned thermal joining method, according to which at least a portion of the second connection section formed from the electrically insulating material is heated, at least locally. As explained in more detail later, such heating can be provided, for example, by a heating device for heating the second connection section, or by radiation, e.g., by means of a laser, but also by mirror welding, friction welding, hybrid welding, or the like.Depending on the design, this enables local, point-like, or linear heating of the second connection section and the creation of a very narrow, even delicate joining contour, as well as large-area melting and, accordingly, the creation of a large-area joining connection to the first connection section. This advantageously provides numerous different application possibilities for the described method. Furthermore, a further finding underlying the invention has been that a material-locking joint provided in this way is not only extremely mechanically stable, but also fluid-tight. Thus, such a thermal joining process can not only create a stable connection between the two connection sections, but, if desired, also a sealing joint between the two connection sections.At least locally heating at least the second connection section is significantly simpler and faster than, for example, the use of adhesives. It is also possible to create much more delicate joints, especially in hard-to-reach areas, which is not possible with conventional injection molding processes or can only be achieved in a very complicated way. Furthermore, no additives such as an adhesive are required for this type of thermal joining process. This allows for savings on additional components, weight, and material. The joint can also be implemented in an extremely space-saving manner and in the tightest of spaces, since no additional material needs to be attached to the joining partners. This therefore provides a particularly efficient joining process and manufacturing method for producing a joining unit, e.g. an energy storage unit of an energy storage device for a motor vehicle.An additional adhesive or sealant can therefore be omitted or at least significantly reduced in quantity. The investment and running costs for curing units, as well as the space, personnel, and energy required for this, can be reduced or eliminated. The molten electrically insulating material, such as a plastic, cures significantly faster than an additionally applied adhesive or sealant. This allows the joined parts to be further processed sooner and with less effort. The risk of the two joined parts losing their relative position is also correspondingly lower. With circumferential connecting seams, a media-tight connection can be created between the parts in addition to positional fixation. In other words, an additional functionality, namely a sealing function, can be integrated using this joining process.

[0009] This idea offers great advantages, above all, in the production of joined components, referred to herein as joining units, in the automotive sector and / or in the production of energy storage devices, such as batteries or fuel cells, e.g. for motor vehicles, but also of stationary energy storage devices, such as stationary fuel cells or stationary batteries, in particular high-voltage batteries. Nevertheless, other applications are also conceivable, e.g. the use of the manufacturing method in the manufacture of electrolyzers or parts thereof, or in the assembly of a motor vehicle, in particular in body production. Although the preferred embodiments of the invention, which are explained in more detail below, largely relate to energy storage applications, the aspects and features explained therein can also apply analogously to other applications.

[0010] In this context, a joining unit refers to a component or part that comprises at least two individual parts joined together, namely the first part and the second part. The joining unit can also be referred to as a joined unit, joined part, joining component, joined component, etc.

[0011] The joining unit can, for example, be a joining unit or a component of an energy storage unit of an energy storage device. The energy storage unit can, for example, be an electrochemical or chemical energy storage unit. The energy storage device can, for example, be designed as a fuel cell and / or as a battery, in particular a high-voltage battery, e.g. for a motor vehicle or as a stationary energy storage device. The first component of the energy storage unit, which has the first connection section made of a metallic material, does not necessarily have to be made entirely of the metallic material, although this can nevertheless be the case. The same applies to the second component.In particular, this does not have to be formed entirely from the electrically insulating material, but has at least the second connection section which is formed entirely from the electrically insulating material.

[0012] The electrically insulating material is at least partially meltable and has a melting point which is lower than that of the metallic material from which the first connection section is made. The electrically insulating material is preferably a plastic or comprises at least one plastic, but it can also be another electrically insulating material, e.g. natural rubber or wax. The second component can be a plastic component, for example. The electrically insulating material can also be a plastic with a filler material, e.g. a fiber-reinforced plastic, e.g. a plastic with embedded fibers, e.g. made of glass, carbon, metal, or the like. The filler material, which can also be made of glass, carbon, metal, or the like, can also be in a form other than fiber, e.g. as a powder, plate, or the like. The filler material does not necessarily have to be meltable orhave a melting point lower than the metallic material from which the first connection section is made. In principle, any plastic can be used as a component of the electrically insulating material. The use of thermoplastics or a thermoplastic material, e.g., polyethylene naphthalate (PEN), is particularly advantageous, which is very useful when the second connection section is designed, for example, as the frame of an MEA (membrane electrode assembly). However, any other plastics are also suitable.

[0013] In principle, any metallic material can also be used.

[0014] This means that the process can be used in many applications where a metallic component needs to be joined to a plastic component, for example, in a mechanically stable and optionally fluid-tight manner.

[0015] Once the first connection section and the second connection section are arranged in contact with each other, there is physical contact between the first and second connection sections. This creates a contact surface between the first and second connection sections. The material-locking joint is created in this contact area, i.e., via this contact surface, after the thermal joining process.

[0016] The thermal joining process is defined such that, when carried out, this joining process leads to at least local heating of the second connection section, preferably at the aforementioned contact surface. This heating is designed such that at least local melting of the electrically insulating material, e.g. the plastic, of the second connection section occurs, in particular in the contact area with the first connection section, i.e. preferably at the aforementioned contact surface. In other words, a part of the electrically insulating material of the second connection section that is in direct contact with the first connection section melts, whereby the material-locking connection to the first connection section is created after the molten electrically insulating material has solidified or hardened again.

[0017] Before the thermal joining process is applied, the second connection section is in a solid state. In other words, the electrically insulating material of the second connection section is solid in this state and not soft or already partially melted or liquefied. The first and second connection sections are thus arranged next to one another in a solid state. Subsequently, the contact surface of the second connection section is partially melted to the first connection section by applying the thermal joining process, according to which at least this part of the second connection section is locally heated.

[0018] Depending on the desired geometric design of the joint, a corresponding geometric configuration for the local heating of the second connection section can be provided according to the thermal joining process. In other words, the joint connection between the two connection sections is ultimately created in the areas that are locally heated. Therefore, if no joint connection is to be created in a specific contact area between the two connection sections, this can be achieved by not heating the second connection section in this area. This also allows for targeted free areas to be provided in the joint, and the joint connection can be designed with geometric flexibility and according to requirements.

[0019] In an advantageous embodiment of the invention, the joining unit of the energy storage unit is produced as a cell separator for placement between two battery cells of the energy storage unit embodied as a battery module. Such a cell separator, often also referred to as a cell separator element, can thus be arranged between two battery cells of a battery module. Such a cell separator serves to spatially separate the battery cells from one another, prevent the spread of fire in the event of a fire occurring in the battery, and, in some cases, also thermally insulate the battery cells from one another. Furthermore, they are used for swelling compensation.The cell separating device can therefore be designed to be elastically deformable in at least one direction, wherein this direction, in a state of the cell separating device installed in the battery module, can correspond, for example, to a stacking direction of a cell stack of the battery module in which the plurality of battery cells of the battery module are arranged next to one another.

[0020] The battery cells may be lithium-ion cells. These are preferably designed as prismatic battery cells and / or pouch cells. These cells therefore have a substantially rectangular geometry in a top view in the stacking direction.

[0021] According to a further very advantageous embodiment of the invention, a cell separation unit is provided as the first component, which has a wall made of the metallic material enclosing an interior space, wherein at least a part of the peripheral edge region of the cell separation unit represents the first connection section. The wall can be designed, for example, as a flexible outer shell. In particular, the wall can be provided by one or two thin metal foils joined together. The two metal foils can be joined together peripherally in the edge region. The interior space enclosed by the wall can be filled with a gas, for example, air. As a result, the cell separation device or the cell separation unit encompassed by it is designed as a type of air-filled cushion or air-filled bag and can accordingly be elastically deformed with respect to the application of pressure.The cell separation unit can therefore be compressed accordingly when the battery cells expand, and expand again accordingly when they contract. The two metal foils mentioned above can be joined together at the edges by a weld.

[0022] In order to withstand the higher pressures in a battery module, the metallic foils must be welded together solidly and the resulting delicate weld seams are subject to high forces, which, as described, emanate from the battery cells.

[0023] It is therefore a further very advantageous embodiment of the invention if at least a first frame part made of the electrically insulating material, in particular of a plastic, is provided as the second component, which represents at least part of the second connection section, in particular wherein the second component additionally has a second frame part which is also part of the connection section, wherein the first frame part and the second frame part are arranged on the part of the edge region of the cell separation unit in such a way that the part of the edge region of the cell separation unit is located between the first and the second frame part. Two functions can be provided simultaneously by the first frame part and in particular also by the second frame part: Firstly, this can advantageously provide electrical insulation of the cell separation device at the edge.It is precisely these edge regions of a cell separator that form part of the outer side of a battery module. The poles of the battery cells are typically also arranged on these outer sides. The edge insulation, which is provided by the at least one first frame part and in particular also by the second frame part, can advantageously provide reliable electrical insulation, especially of the cell poles and the cell connectors. A further additional function that can be provided by the first frame part, which is or will be joined to the cell separator unit using the thermal joining method, is that it can thereby provide an incompressible spacer in the edge region of the cell separator, e.g. in the form of an incompressible frame running all the way around the cell separator.This allows a certain minimum distance to be provided between the battery cells in the edge region and defined by the thickness of the cell separation device in this edge region. This prevents, for example, the cells from being compressed too strongly during assembly of the battery module or cell stack, which could also flatten the cell separation unit. The cells can therefore advantageously be held at a defined minimum distance from one another by the cell separation device. A particularly great advantage of the first frame part and in particular also of the second frame part is that the weld seams described above, or in general the joints between the two metal foils for providing the cell separation unit, can be stabilized and supported by this plastic frame.Especially when installed in the battery module, this additional plastic frame exerts a compressive force via the cells onto these weld seams or joints between the metal foils, and the metal foils are additionally sealed and stabilized in their peripheral edge area by being compressed in the area of ​​the weld seams. The probability or risk of leaks in the separating elements in the edge area or in the area of ​​the joints between the metal foils can thus be significantly reduced, and a resulting loss of function of the cell separating elements can be prevented. Furthermore, the described thermal joining process can be used to join the frame parts and the cell separating unit in the edge area to form a single unit, particularly with a material bond.This non-detachable connection makes the components easier to handle and ensures that the safety function of the electrical insulation is maintained where necessary. Slipping or similar problems are thus eliminated. Furthermore, handling and positioning of the components in subsequent processes, such as subsequent module assembly, is simplified.

[0024] According to a further advantageous embodiment of the invention, it is provided that the first frame part and the second frame part, after being arranged on the part of the edge region, each protrude beyond the edge region, wherein in the thermal joining process the edges of the first and second frame parts protruding beyond the edge region are additionally joined to one another, in particular fused to one another.

[0025] The two frame parts can therefore advantageously be fused together in the protruding edge area using the same joining process, creating a frame unit that encompasses or encloses the cell separation unit at the edge. Viewed in cross-section, the two joined frame parts then result in a U-shaped geometry. The outer edge of the cell separation unit is thus enclosed by the plastic frame, or encompassed or enclosed by the fused part of the two frame parts. This also provides particularly reliable and secure insulation of the edge of the cell separation unit.

[0026] The frame or the first and second frame parts can, for example, have a rectangular geometry. In this case, the first and second frame parts run around the edge region of the cell separation unit along a closed contour. However, it is also conceivable to design the frame so that it is only provided on two opposite sides or edges of the cell separation unit. In this case, it can also be provided that the frame is not provided by two frame parts joined together, but by a first frame part which, for example, is placed around a first edge of the cell separation unit, enclosing or encompassing it in a U-shape, and is then joined to this edge on both sides using the thermal joining process. The same procedure can be repeated for a second frame part on the opposite side edge of the cell separation unit.

[0027] The frame part, both the first and the second frame part, can generally be very thin and can be provided, for example, in the form of a plastic film or a film made of another electrically insulating material.

[0028] In a further advantageous embodiment of the invention, the cell separation unit is arranged between two battery cells, so that a minimum distance between a first cell edge region of the first battery cell and a second cell edge region of the second battery cell is defined by the thickness of the cell separation unit in the region of the joined frame parts. This advantageously allows the joined frame parts to simultaneously provide an incompressible spacer in the edge region of the cells.

[0029] The surrounding frame, which is provided by at least a first frame part, can also be partially recessed for certain applications.

[0030] In a further advantageous embodiment of the invention, a joining unit or component of a fuel cell stack, in particular a unit cell of a fuel cell stack, which represents the energy storage unit, is produced as the joining unit of the energy storage unit. In conventional fuel cells, media-tight spaces usually have to be created. Seals are also typically used, which take on this function when pressed together, or non-detachable connections by applying additional adhesive between the partners to be joined or by welding the individual metallic plates, or a combination of these methods. Frequently, so-called MEAs (membrane electrode assemblies), i.e. membrane electrode units, are connected to individual plates or bipolar plates. In the context of the present invention, individual plates refer to single-pole plates.The MEA is usually constructed in such a way that the CCM (catalyst coated membrane), i.e., the catalyst-coated membrane of the reaction zone, is embedded in a plastic frame, e.g., made of PEN. This advantageously allows such an MEA to be joined to an adjacent metallic plate, e.g., a bipolar plate or a single plate, using a thermal joining process as described above, while simultaneously sealing it against this plate. This can also result in enormous advantages in terms of time savings, material savings, and efficiency in the production of such a fuel cell unit.

[0031] Therefore, a further very advantageous embodiment of the invention provides a metallic plate, in particular a bipolar plate or single plate, as the first component, wherein the first connection section is provided by at least part of an edge region of the plate. Furthermore, a membrane electrode assembly, namely the MEA described above, is provided as the second component, wherein the second connection section represents a frame of the membrane electrode assembly that surrounds a reaction region of the membrane electrode assembly, in particular wherein the thermal joining connection between the first and second connection sections provides a fluidic seal between the first and second connection sections.

[0032] Advantageously, the described thermal joining process eliminates the need for prior injection molding of a plastic frame around such a plate, for example, a bipolar plate or single plate. Such a plate can then simply be placed on the corresponding MEA, and subsequently, the MEA can be partially melted by heating in the edge area or in the area of ​​its frame made of the electrically insulating material, in particular its plastic frame, in order to create a sealed joint to the plate.

[0033] A unit cell of a fuel cell has a membrane electrode assembly, which can also be referred to as a membrane electrode arrangement, and additionally either a bipolar plate or alternatively two individual plates arranged on opposite sides of the membrane electrode assembly. In principle, the structure of a bipolar plate can be similar or equivalent to the structure of two individual plates. A fuel cell or a fuel cell stack can be formed by stacking several such unit cells. Between two MEAs there are then either two individual plates or a bipolar plate. The ends of the stack can be delimited by individual plates. A free space through which flow can take place, for example in the form of channels, can be formed between the individual plates or within the bipolar plate. Accordingly, two adjacent individual plates can also be joined together in a sealing manner.Joining methods known from the prior art can be used for this purpose. If a respective unit cell comprises an MEA and a bipolar plate, the individual unit cells can also be joined together using the thermal joining method to form the fuel cell, namely by partially melting the plastic of the plastic frame of the associated MEA located between two bipolar plates. The MEA and bipolar plate can be layered successively, and after each additional layer, a thermal joining process can be carried out for bonding, i.e., for the material-locking connection of the plastic frame of the MEA to the adjacent bipolar plate, as described.

[0034] A combination of the described thermal joining process with conventional joining processes such as bonding or adhesive seals to form a fuel cell stack is also conceivable.

[0035] The plates, i.e., the individual plates and / or bipolar plates, can generally be very thin, for example, foil-like. Furthermore, media ports can be integrated into the plates and the corresponding frame parts of the MEAs as through-holes or recesses. These media ports can be used to supply and remove media to and from the reaction zone, as well as to supply and remove cooling water. However, the media supply and removal can also be realized through external channels that are flanged to the fuel cell stack. The joining connection between an MEA and an adjacent metallic plate can be designed depending on the situation and requirements. For example, this joining connection can be provided by a closed, circumferential joining contour.In addition, such a contour or another contour, for example one surrounding the media ports, can be provided with corresponding interruptions to create passage areas for the media. By using the thermal joining process in such a fuel cell, in particular for producing a fuel cell unit, an additional sealing effect between the metallic plate and the MEA can be created by the molten frame material, i.e. the electrically insulating material of the MEA frame. Additional sealing material can thus advantageously be omitted, and the sealing function is easy to implement. Furthermore, the risk of a short circuit at the alignment points can be reduced. The number of individual components to be stacked is reduced by the prior formation of an assembly consisting of the MEA and bipolar plate or individual plates.The MEA gains stability through the welded bipolar plate or individual plates. Furthermore, quality assurance during the stacking process can be simplified, particularly through simpler technical implementation of the measurement technology. For example, only one sensor for the metallic edge is sufficient for measurement. By sealing the two components together—that is, the MEA and at least one metallic plate—a new "module" is created that simplifies the stacking process, handling, and the logistics chain.

[0036] In a further advantageous embodiment of the invention, a component of a stationary energy storage device is produced as the joining unit. This stationary energy storage device can in turn be designed as a battery, in particular a high-voltage battery, as already described above, or a fuel cell, as also described above.

[0037] In a further advantageous embodiment of the invention, a part of an electrolyzer is produced as the joining unit. For example, the structure of an electrolyzer is similar to that of a fuel cell. An electrolyzer comprises several electrolysis cells arranged in a row, in which the necessary redox reaction takes place through supplied electrical energy. Such an electrolysis cell can accordingly represent the joining unit. Such an electrolysis cell can also have a membrane with a surrounding frame, as well as plates arranged on one or both sides of it, e.g. two individual plates or a bipolar plate. The plates can be made of a metallic material and the frame of the membrane unit can be made of an electrically insulating material, e.g. plastic. Several of these joining units can be stacked to provide the electrolyzer, in particular analogously to that described for the fuel cell.

[0038] In a further advantageous embodiment of the invention, a component of a motor vehicle is produced as the joining unit during vehicle assembly, in particular during body construction. The described method also offers significant advantages in body construction. The joining unit can accordingly represent a component of the body of such a vehicle. For example, to produce such a body component, a metallic component can be joined as the first component to a film made of an electrically insulating material, e.g., a plastic film, as the second component.

[0039] In a further advantageous embodiment of the invention, the thermal joining takes place by means of a heating device which is brought into physical contact with the first and / or second connection section, in particular with the first connection section, and is heated. This procedure is particularly suitable when larger-area joints are to be provided. By physically arranging such a heating device on a corresponding connection section, this section can also be stabilized. The heating device can simultaneously function as a support and be used, for example, to exert additional pressure during the joining process. It is preferred to arrange the heating device on the first connection section and not on the second connection section.The heat from the heating device can be transferred directly to the second connection section made of electrically insulating material via the metallic first connection section, causing it to melt in a targeted manner. This also prevents the heating device from sticking to the second connection section itself. Furthermore, the electrically insulating material of the second connection section is melted in the contact area with the first connection section, or melts first or most intensely, and thus precisely where the material-to-material joint is to be created, namely at the contact surface with the first connection section.

[0040] According to a further advantageous embodiment, the thermal joining is carried out by means of a laser, by means of whose radiation the first and / or second connection section is at least locally heated. This laser or the radiation provided by the laser can, for example, be directed directly at the second connection section to heat it. This allows for targeted melting of the second connection section. However, the laser beam is preferably not directed directly at the second connection section, but rather also preferably at the first connection section. The local heating of the metal of the first connection section then leads directly to the local heating of the corresponding, contacting region of the second connection section and to its melting.

[0041] The use of a laser avoids direct physical contact with the second attachment section, and in particular with the first attachment section, and sticking is prevented even in the case of direct action on the second attachment section.

[0042] Furthermore, the use of a laser can create a particularly delicate and thin joining contour. Especially in the case of the cell separation element, this procedure also allows, for example, the simultaneous creation of the joining connection between a frame part and the cell separation unit, as well as the simultaneous creation of the joining connection between the two metallic foils that form the cell separation unit or are components of it.

[0043] In general, thermal joining processes that are suitable are heat conduction processes that heat the surfaces to be joined either through direct contact and melt the electrically insulating material in the mold (e.g. mirror welding), so that this material then bonds with the joining partner, for example through the application of additional pressure. Heat can also be introduced via a laser beam. This, for example, heats the metal in the mold at the points where the electrically insulating material is to be joined, so that the electrically insulating material melts there and forms a bond with the metal. The bond can be optimized by applying additional pressure. With a circumferential seam, this can also create a media-tight connection. Other heat conduction processes such as induction are also possible.

[0044] Furthermore, the invention also relates to a joining unit, in particular for an energy storage unit of an energy storage device for a motor vehicle, wherein the joining unit was produced by means of a method according to the invention or one of its embodiments.

[0045] In particular, the invention also relates to a joining unit, e.g., for an energy storage unit of an energy storage device for a motor vehicle, wherein the joining unit comprises a first component having a first connection section formed from a metallic material, and a second component having a second connection section formed from an electrically insulating material, e.g., plastic. The first connection section and the second connection section are arranged in contact with one another and are joined to one another in a material-locking manner via an at least melted and resolidified region of the second connection section.

[0046] The advantages described for the method according to the invention and its embodiments apply equally to the joining unit according to the invention.

[0047] The invention also includes further developments of the joining unit 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 joining unit according to the invention are not described again here.

[0048] The invention also includes an energy storage unit and / or an energy store with a joining unit according to the invention or one of its embodiments, as well as a motor vehicle with a joining unit according to the invention or one of its embodiments, wherein a motor vehicle with an energy store according to the invention or one of its embodiments.

[0049] 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.

[0050] According to a further embodiment, the energy storage unit can also represent a stationary energy storage device.

[0051] Furthermore, the invention also relates to an electrolyzer with a joining unit according to the invention or one of its embodiments.

[0052] 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.

[0053] Exemplary embodiments of the invention are described below. Shown are: Fig. 1 a schematic representation of individual method steps for producing a cell separation device according to an embodiment of the invention; Fig. 2 a schematic cross-sectional view of a part of a manufactured cell separator between two battery cells according to an embodiment of the invention; Fig. 3 a schematic representation of several cell separation devices during the manufacturing process according to another embodiment of the invention; Fig. 4 a schematic and perspective illustration of a fuel cell unit with an MEA joined to a bipolar plate via a reflow process according to an embodiment of the invention; Fig. 5 shows a schematic representation of individual manufacturing steps for producing a fuel cell unit with a bipolar plate and an MEA according to an embodiment of the invention; and Fig. 6 a schematic representation of the individual process steps for producing a fuel cell unit with an MEA and two individual plates according to a further embodiment of the invention.

[0054] 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.

[0055] In the figures, the same reference symbols designate elements with the same function.

[0056] Fig. 1 shows a schematic representation of individual process steps for producing a cell separation device 10 according to an exemplary embodiment of the invention. The cell separation device 10 is an example of a joining unit, e.g., an energy storage unit of an energy storage device for a motor vehicle. In this example, the energy storage unit represents a battery module, and the energy storage device, for example, a high-voltage battery for the motor vehicle. The energy storage device can also represent a stationary energy storage device. The cell separation device 10 comprises a cell separation unit 12. This, in turn, comprises an outer shell 14, which encloses an interior space. The outer shell 14 is metallic and, in the present example, is provided by two foils 16a, 16b joined to one another. The foils 16a, 16b can be pre-embossed to form a bulged, three-dimensional structure.The foils are joined together, for example, welded, in an edge region 20 by a corresponding joining contour 22. This circumferential weld seam 22 can be composed of individual weld seam sections, which in this example are designed to run in a straight line and overlap. The joining of the two metal foils 16a, 16b to form the cell separation unit 12 takes place in a first process step S10. In a subsequent second process step S12, two frame parts, namely a first frame part 24a and a second frame part 24b, are provided. These are each rectangular in shape. The length and width of each frame part 24a, 24b can essentially correspond to a length and width of the cell separation unit 12.Preferably, however, the frame parts 24a, 24b are designed to be somewhat longer and wider than the cell separation unit 12, so that the frame parts 24a extend beyond the edge region 20 at least in sections and at least on one side of the cell separation unit 12, and in the present example, on all sides. The frame parts 24a, 24b are made of an electrically insulating material, which in this and the examples explained below is a plastic, but can in principle also be another electrically insulating, meltable material. The frame parts are now arranged in the edge region 20 of the cell separation unit 12.If these are arranged as intended in the edge region 20, in particular covering the weld seam 22, in particular covering both sides, on the cell separation unit 12, as shown, for example, in the subsequent step S14, the two frame parts 24a, 24b are joined to the edge region 20 of the cell separation unit 12 and, at the same time, are materially connected to one another in the projecting edge region. Joining is carried out using a thermal joining process designed such that the frame parts 24a, 24b are melted at least in some areas. In addition, pressure can be exerted on the respective frame parts 24a, 24b in the direction of the intermediate edge region 20 of the cell separation unit 12. The partially melted plastic bonds to the metallic material in the edge region 20 at the contact surface with the edge region 20 of the cell separation unit 12.This creates an extremely stable connection between the frame parts 24a, 24b and the cell separation unit 12. Furthermore, this simultaneously allows the two frame parts 24a, 24b to fuse together in their protruding edge regions. As a result, the metallic edge 18 surrounding the cell separation unit 12 is completely covered by the plastic of the frame parts 24a, 24b. The metallic edge 18 surrounding the cell separation unit 12 can thus be reliably electrically insulated from the outside. The cell separation device 10 thus completed can then be arranged between two battery cells of a battery module or for the production of a battery module.

[0057] Fig. Figure 2 shows a schematic cross-sectional view of a portion of such a cell separator 10 in a state arranged between two battery cells 28 of a battery module 30. The battery cells 28 can be designed, for example, as prismatic battery cells. The cell walls adjacent to the cell separator 10 are designated 28a in this case. Fig. Figure 2 again shows the outer shell 14 of the cell separation unit 12, which surrounds or encloses the interior space 32 of the cell separation unit 12. The interior space 32 can be gas-filled, in particular air-filled. This gives the cell separation unit 12 a certain flexibility and elastic deformability in the central region. The outer shell 14 is again, in particular as shown in Fig. 1 and comprises two films 16a, 16b, which are joined together via a welded connection 22 along a weld contour 22. The edge region of the joined films 16a, 16b is again designated 20. This edge region 20 is now enclosed by a plastic frame 24. This frame 24 completely covers the metallic edge 18 of the outer shell 14. The frame 24 can in turn optionally consist of two films 24a, 24b. The frame 24 can, as previously described, have been joined to the edge region 20 of the cell separation unit 12, namely by a thermal joining process in which part of the plastic of the frame 24 is melted and thus bonded to the metallic material of the cell separation unit 12 in the edge region 20, optionally with additional pressure. The heating of the plastic of the frame 24 only takes place for a limited time.Once the plastic material has melted sufficiently, the heating process can be stopped. If the frame 24 is pressed against the corresponding surfaces of the edge region 20 of the cell separation unit 12, the molten plastic material of the frame 24 solidifies again and forms a very stable bond with the metal in the edge region 20 of the cell separation unit 12. As shown in . Fig. 2, the projecting edges of the respective films 24a, 24b are also fused together, so that the edge 18 is also covered with plastic.

[0058] In principle, it is also conceivable for the frame not to extend completely around the edge region 20 of the cell separation unit 12. It would also be conceivable to provide such a frame 24 only on opposite edge regions 20, for example, at the top and bottom of the cell separation unit 12 or on the left and right of a cell separation unit 12. The frame 24 can then, for example, also be provided solely by a plastic component, for example, a plastic film wrapped around the edge region 20, which is fused to the metal in the edge region 20 of the cell separation unit 12 by heating.

[0059] In addition to a circumferential frame 24, application to selected edges of the cell separation unit 12 is also conceivable. For example, in series production it is advisable to implement a continuously running process. If, for example, such a frame element 24 is to be applied to a specific edge of the cell separation unit 12, this can be implemented for this edge in such a way that two plastic bands or strips are applied to the upper and lower sides of the sheets that form the cell separation unit 12, in the respective edge areas. The two plastic bands or strips are therefore arranged on opposite sides in the edge area of ​​the cell separation unit 12. These plastic bands or strips are connected to the sheet or additionally to one another by means of pressure rollers, for example. For this purpose, the plastic bands or strips can protrude over the edge of the sheets. This then leads to a U-shaped lap of the sheet edge after joining.

[0060] This procedure can also be used for series production by providing several cell separation units 12, which are arranged next to each other and in particular are not yet separated from each other, with the corresponding plastic bands or strips at the same time, similar to the one shown in Fig. 3 and described below.

[0061] Fig. 3 shows a schematic representation of several cell separation devices 10 during the manufacturing process according to a further exemplary embodiment of the invention. The cell separation devices 10 can be designed as described above. In the present example, several cell separation devices 10 can be manufactured simultaneously. For this purpose, for example, the cell separation units 12 can be formed from a common first metal foil 16a' and a common second metal foil 16b' by joining them, for example by laser welding, in a respective edge region 20. Subsequently, or in a same process step, the frame parts 24a, 24b, initially designed as a one-piece overall frame, can be placed on both sides of the respective cell separation units 12, as in Fig. 3, and then joined to the cell separation units 12 by laser welding along a circumferential contour by means of a laser 34 and a laser beam 36 provided thereby.

[0062] Alternatively, instead of a frame, plastic bands or strips can be applied to both sides of the edges so that they extend over the edges of the multiple cell separation units. Furthermore, joining can generally also be achieved using the aforementioned pressure rollers, which move over the plastic bands applied to the edges, particularly on both sides, so that, for example, between such a pair of rollers are located the two edges of the metal sheets forming the cell separation units 12, as well as an upper plastic strip and a lower plastic strip, between which the edges of the two metal sheets of the cell separation units 12 are located. As an alternative to joining using the pressure rollers, laser welding or other welding methods can also be used.

[0063] Subsequently, the cell separation devices 10 thus manufactured can be separated from one another, for example by a separation process, for example by cutting apart or the like.

[0064] Fig. 4 shows a schematic representation of another example of a joining unit 40 of an energy storage unit for an energy storage device, e.g., of a motor vehicle or for a stationary energy storage device. In this example, the joining unit 40 is designed as a fuel cell unit 40. This comprises a so-called MEA 42, namely a membrane electrode assembly 42, which in this case is arranged on a bipolar plate 44 and joined to it. The MEA 42 comprises a centrally arranged reaction region 46 and a plastic frame 48 surrounding it. Recesses 50 are arranged in this plastic frame 48 and correspondingly in the bipolar plate 44 arranged underneath, through which media ports are provided. These serve for the media supply and removal, in particular for the cooling water as well as for the reactants or starting materials of the reaction, i.e. for the reaction products.The MEA 42 and such a bipolar plate 44 can generally be designed as known from the prior art. Typically, such an MEA 42 is joined to a bipolar plate 44 using adhesives and / or sealants. The particularly fluid-tight connection between the MEA 42 and the bipolar plate 44 can now advantageously also be produced using the thermal joining method already described. This joining connection is in turn achieved by at least locally melting a portion of the plastic of the frame 48 of the MEA 42. The molten plastic then bonds accordingly to the underlying bipolar plate 44, in particular in an edge region thereof or along the desired joining contours. The joining connection provided by the molten plastic is designated 52 in the present case.On the one hand, this is arranged circumferentially in the edge region 48a of the frame or the edge region 44a of the underlying bipolar plate 44 and, in this example, also surrounds the recesses 50 for the media ports. The joint 52 can also be partially interrupted, for example, to allow for media supply and / or removal, e.g., into a space between the MEA 42 and the bipolar plate 44.

[0065] An exemplary manufacturing method for producing such a fuel cell unit 40 is exemplified in Fig. 5 shown. Fig. 5 again shows the individual process steps during the manufacture of such a fuel cell unit 40, which in the present example again comprises an MEA 42 and a bipolar plate 44, or is formed by the MEA 42 and the bipolar plate 44. In a first step S16, the MEA 42 and the bipolar plate 44 are first provided. In the present example, the bipolar plate 44 is made entirely of metal. The frame 48 of the MEA 42 is made entirely of plastic and, as described, surrounds the reaction area 46, which is rectangular in the present example.The bipolar plate 44 can also be divided into a reaction region 44b and a surrounding frame region 44a, so that when positioned one above the other, as occurs in step S18, the edge region 44a of the bipolar plate 44 rests in direct contact with the edge region 48 of the MEA 42, and the corresponding reaction regions 44b, 46 also lie one above the other in the correct position. Subsequently, in step S20, this arrangement is positioned on a support element 54, which simultaneously represents a heating device 56. This is heated accordingly in step S22 and thus transfers the heat to the bipolar plate 44, which in turn transfers the heat to the MEA 42 located above it, whereby the plastic in its edge region 48 is partially melted.During heating, as occurs in step S22, a force F, in particular a contact force, can additionally be exerted on the arrangement of MEA 42 and bipolar plate 44, i.e., simultaneously or overlappingly. This presses the corresponding edge regions 44b, 46 together. The melted plastic of frame 48 of MEA 42 thus bonds stably and materially to the metallic material of frame region 44a of bipolar plate 44.

[0066] In step S24, the heat supply via the heating device 56 is initially stopped, as is the application of compressive force. Furthermore, the heating device 56, as well as the pressing structure 58, which can be placed on top of the frame region 48 of the MEA 42 to provide the application of compressive force with force F, can be removed again, e.g., after the molten plastic has solidified again. Finally, in step S24, the fuel cell unit 40 is provided, in which the MEA 42 is now joined to the bipolar plate 44 via the molten and resolidified plastic 52.

[0067] A fuel cell unit 40 can be formed not only from an MEA 42 and a bipolar plate 44, but alternatively also from an MEA 42 and two individual plates 44`, as shown in Fig. 6 is illustrated schematically.

[0068] In particular, Fig. 6 shows individual process steps for producing a fuel cell unit 40` according to a further embodiment of the invention, wherein the fuel cell unit 40` now consists of the MEA 42 and two individual plates 44`. The MEA 42 can be designed as previously described and is positioned between the two individual plates 44` to provide the fuel cell unit 40`. The recesses in the individual plates 44 for the media ports are designated 50` in this case. The manufacturing process for the fuel cell unit 40` can be carried out in a manner analogous to Fig.5 and is therefore only briefly explained below: In step S16`, the two individual plates 44` and the MEA 42 are first provided. The individual plates 44 can also have a central reaction region 44b` and an edge region 44a`. In step S18`, the individual plates 44` and the MEA 42 are arranged one above the other in the correct position so that the plates 44 are each in direct contact with the MEA 42, in particular the corresponding edge regions 44a` and 48. In step S20`, this arrangement is placed on a support 54, which in turn is simultaneously designed as a heating device. Furthermore, in step S22`, the printing support 58 is then placed on the other side of this arrangement onto the upper individual plate 44`. Furthermore, in this example, the printing support 58 is now also simultaneously designed as a heating device 56`.In step S22', the two heating devices 56, 56' are activated, or via them, the individual plates 44' and thus the MEA 42 in the edge region 48 are heated, at least locally. Furthermore, a compressive force F is simultaneously exerted on the assembly, so that the MEA 42 is compressed between the individual plates 44', at least in the corresponding edge regions 48. Subsequently, the heating is deactivated, and the compressive force F can also be terminated after the molten plastic of the frame region 48 of the MEA 42 has cured or resolidified. Subsequently, the heating devices 56, 56' can be removed, and the joined fuel cell unit 40' can be provided in step S24'.

[0069] The melting of the plastic in the edge region 48 of the MEA occurs via heat conduction, in particular via the individual plates 44', or via the previously described bipolar plate 44. Instead of a large-area heating device, the edge region 44a' of the individual plates 44' or the edge region 44a of the bipolar plate 44 can also be heated only locally in a targeted manner in order to achieve targeted and exclusively local melting of the plastic of the frame 48 of the MEA 42. This can be achieved by a special geometric shape of the heating device 56, or alternatively by laser welding.

[0070] Overall, the examples demonstrate how the invention provides for joining components for battery, fuel cell, and electrolyzer manufacturing, and in particular for welding plastics to metal surfaces to implement properties. 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 100 25 207 A1

[0003] DE 10 2007 007 986 A1

[0004]

Claims

[1] Method for producing a joining unit (10, 40, 40'), in particular for an energy storage unit (30) of an energy storage device for a motor vehicle, - wherein a first component (12, 44, 44') (30) is provided which has a first connection section (20, 44a, 44a') formed from a metallic material; - wherein a second component (24, 24a, 24b, 42) is provided which has a second connection section (24, 24a, 24b, 48) formed from an electrically insulating material; characterized by that the first connecting section (20, 44a, 44a') and the second connecting section (24, 24a, 24b, 48) are arranged in contact with one another and are joined to one another in a material-locking manner by means of a thermal joining process, according to which at least the second connecting section (24, 24a, 24b, 48) is heated at least locally. [2] Method according to claim 1, characterized bythat a cell separating device (10) of an energy storage unit (30) for arrangement between two battery cells (28) of the energy storage unit (30) to be designed as a battery module (30) is produced as the joining unit (10, 40, 40'). [3] Method according to claim 2, characterized by , that - a cell separation unit (12) is provided as the first component (12), which has a wall (14) made of the metallic material enclosing an interior space (32), wherein at least a part of a peripheral edge region (20) of the cell separation unit (12) represents the first connection section (20); - at least one first frame part (24, 24a, 24b) made of the electrically insulating material, in particular a plastic, is provided as the second component (24, 24a, 24b), which represents at least a part of the second connection section (24, 24a, 24b), in particular wherein the second component (24, 24a, 24b) additionally has a second frame part (24, 24b, 24a), which is also part of the second connection section (24, 24a, 24b), wherein the first frame part (24, 24a, 24b) and the second frame part (24, 24b, 24a) are arranged on the part of the edge region (20) of the cell separation unit (12) in such a way that the part of the edge region (20) of the cell separation unit (12) is located between the first and the second frame part (24, 24a, 24b). [4] Method according to claim 3, characterized bythat the first frame part (24, 24a, 24b) and the second frame part (24, 24b, 24a) project beyond the edge region (20) after being arranged on the part of the edge region (20), wherein in the thermal joining process the edges of the first and second frame parts (24, 24a, 24b) projecting beyond the edge region (20) are additionally joined to one another. [5] Method according to one of claims 2 to 4, characterized by that the cell separating device (10) is arranged between two battery cells (28), so that a minimum distance between a first cell edge region of the first battery cell (28) and a second cell edge region of the second battery cell (28) is defined by a thickness of the cell separating device (10) in the region of the joined frame parts (24, 24a, 24b). [6] Method according to claim 1, characterized bythat a joining unit (40, 40') of a fuel cell stack, in particular a unit cell (40, 40') of a fuel cell stack, which represents the energy storage unit, is produced as the joining unit (40, 40') of the energy storage unit. [7] Method according to claim 6, characterized by , that - a metallic plate (44, 44'), in particular a bipolar plate (44) or single plate (44'), is provided as the first component (44, 44'), wherein the first connection section (44a, 44a') is provided by at least part of an edge region (44a, 44a') of the plate (44, 44'); - a membrane electrode unit (42) is provided as the second component (42), wherein the second connection section (48) represents a frame (48) of the membrane electrode unit (42) which surrounds a reaction region (46) of the membrane electrode unit (42), in particular wherein a fluidic seal (52) between the first and second connection sections (44a, 44a', 48) is provided by the thermal joining connection (52) between the first and second connection sections (48). [8] Method according to one of the preceding claims, characterized by that as the joining unit (44, 44') an electrolyzer or a joining unit of a stationary energy storage device (30) or a joining unit of a motor vehicle is produced during motor vehicle assembly. [9] Method according to one of the preceding claims, characterized bythat the thermal joining is carried out by means of a heating device (56, 56') which is brought into physical contact with the first and / or second connecting section (20, 24, 24a, 24b, 44a, 44a', 48), in particular with the first connecting section (20, 44a, 44a'), and is heated. [10] Method according to one of the preceding claims, characterized by that the thermal joining is carried out by means of a laser (34), by means of whose radiation (36) the first and / or second connection section (20, 24, 24a, 24b, 44a, 44a', 48) is heated at least locally. [11] Joining unit (10, 40, 40'), in particular for an energy storage unit (30) for an energy storage device for a motor vehicle, wherein the joining unit (10, 40, 40') was produced by means of a method according to one of the preceding claims.

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