Cell separating element

Abstract

The invention relates to a cell separating element, having a housing (1) in which a fluid is provided and which is formed by two film-like housing parts (2, 3). These are connected to one another in a sealingly fixed manner along their edge (4, 5), wherein at least one integral connection (13) running over the length of the edge (4, 5) is provided in the edge region. Said connection is covered by an elastically deformable cover part (14) which is provided on the edge (4, 5) of the housing.

Description

[0001] Cell separation element

[0002] The invention relates to a cell separation element according to the preamble of claim 1.

[0003] Such cell separators are used in energy storage systems for motor vehicles. The energy storage system consists of battery cells arranged next to and / or on top of each other, between which the cell separators are placed to separate them electrically and thermally. The cell separator serves, on the one hand, to absorb swelling forces. Swelling is a phenomenon whereby the cells swell over their lifetime. This aging-related swelling is also superimposed by charge-related swelling, which causes the cells to swell during charging and shrink again during discharging.

[0004] It also happens that a battery cell in the energy storage system fails, causing it to overheat and emit gases. In this case, the cell separators prevent neighboring battery cells from overheating.

[0005] These cell separators have two film-like housing parts that define a space for a fluid, which can be a gas or a liquid. These housing parts are welded together across the edge of the cell separators (DE 10 2019 130 499 A1). The fluid in the space allows external forces acting on the cell separator to be easily absorbed and compensated for. In addition, the fluid at least reduces the risk of a neighboring battery cell or possibly the entire energy storage device being damaged by a battery cell that is too hot. However, with this known cell separator there is a risk that under corresponding pressure the housing parts will separate in the area of ​​the welded joint, causing the contents of the cell separator to leak out.

[0006] The invention is based on the object of designing such a cell separation element in such a way that, with simple manufacturing and structural design, it ensures a reliable, temporally homogeneous pressure distribution on the cells, which has a positive effect on the service life and aging behavior of the cells. Furthermore, the separation of adjacent components during their deformation under the influence of heat should be ensured.

[0007] This object is achieved according to the invention in the generic cell separation element with the characterizing features of claim 1.

[0008] In the cell separator according to the invention, the cover part ensures that, in the event of a corresponding volume expansion of the cells or the housing components, the two edges of the housing parts do not diverge in the area of ​​the welded joint. The cover part absorbs the volume expansion of the housing parts through corresponding elastic deformation, while the pressure occurring during the elastic deformation is diverted to the weld seam, so that the edges of the housing parts do not diverge from each other in the area of ​​the weld seam. The edges therefore remain adjacent to each other in the area of ​​the welded joint and do not diverge from each other.

[0009] A secure attachment of the cover and optimal compressive load on the weld seam are achieved when the cover extends at least close to the outer peripheral side of the housing edge. This design allows the cover to be reliably attached to the edge of the housing. Depending on the application, it is advantageous to have the cover on the top and bottom of the housing edge.

[0010] With such a design, the two cover parts on the top and bottom sides of the housing edge can be separated from each other. However, a preferred design is when the cover parts provided on both sides of the housing edge are formed integrally with each other.

[0011] This one-piece design is advantageously achieved by the housing edge having perforations distributed around its circumference, through which the material of the cover part extends. The areas of the cover part extending through the perforations contribute to its secure attachment to the housing edge.

[0012] However, it is also possible to form the two cover parts on the top and bottom as a single piece, with the material of the cover part encompassing the outer peripheral surface of the housing edge. In this case, the openings in the housing edge are not necessary. However, the openings can of course also be provided additionally, which contributes to a secure attachment of the cover part to the housing edge.

[0013] An optimal design is achieved when the cover part is thickened in the area of ​​the welded joint. This provides sufficient material for elastic deformation of the cover part to reliably prevent the edges of the housing parts from separating in the area of ​​the welded joint. The outer side of the thickened area of ​​the cover part is advantageously roof-shaped. The thickened area can then be arranged on the housing edge so that the welded joint is at the height of the roof edge.

[0014] In an advantageous embodiment, a region of the cover part extending from the thickened region toward the outer peripheral side of the housing edge has a constant thickness. This region of the cover part can be used to securely hold or fasten the cover part to the housing edge. It is advantageous if this region of constant thickness extends to the outer peripheral side of the housing edge. Then, since the cover part and thus the region of constant thickness extend across the width and circumference of the housing edge, the housing edge is also protected over most of its width and circumferential length.

[0015] A secure connection of the cover part to the housing edge is advantageously achieved if the cover part is connected to the housing edge in a flat manner.

[0016] The housing parts are preferably made of metal foils.

[0017] To form the housing, the metal foils are plastically deformed, preferably by a deep-drawing process. The metal foils can be deformed in such a way that a pillow-shaped cell separator is formed when the two housing parts are firmly connected to each other at their edges.

[0018] The cover is preferably made of rubber or a rubber-like material. It is inexpensive, easy to attach to the housing, and allows for easy elastic deformation.

[0019] The housing parts advantageously have a thickness of only between approximately 0.3 mm and approximately 1.2 mm, preferably 0.7 mm. These wall thicknesses are sufficient, especially for metallic foils, to ensure adequate housing strength.

[0020] The fluid contained in the housing is a gas or a liquid. The gas is preferably a noble gas, preferably helium. Flame retardants or fire-protection fluids can also be provided in the housing. Examples include ammonium phosphate, aluminum hydroxide, magnesium hydroxide, triphenyl phosphate, and triethyl phosphate.

[0021] The subject matter of the application arises not only from the subject matter of the individual patent claims, but also from all information and features disclosed in the drawings and the description. Even if they are not the subject matter of the claims, they are claimed as essential to the invention insofar as they are novel, individually or in combination, over the prior art.

[0022] Further features of the invention emerge from the further claims, the description and the drawings.

[0023] The invention will be explained in more detail with reference to an embodiment shown in the drawings.

[0024] Fig. 1 in plan view a cell separation element according to the invention

[0025] Fig. 2 is a section along the line A - A in Fig. 1,

[0026] Fig. 3 shows an enlarged view of section B in Fig. 2,

[0027] Fig. 4 shows a schematic representation of a cell separator element according to the invention, located between two components, in the assembled state, with its cover part elastically deformed. The cell separator element is designed like a gas-filled cushion. In the exemplary embodiment described below, it has a rectangular outline, but depending on the application and / or installation conditions, it can also have a different outline shape, for example, oval.

[0028] The cell separation element has a housing 1 which is formed by two foils 2, 3 which, in the example, have a rectangular outline and are firmly and tightly connected to one another along their edges 4, 5 (see also Fig. 3).

[0029] The foils 2, 3 are advantageously metal foils. In the following, the foils 2, 3 are referred to as metal foils, although they may also be made of, for example, a suitable plastic, fiber-reinforced plastic, fiber-composite materials, or an elastic ceramic, etc. The area in which the edges 4, 5 abut one another is advantageously of the same width over the circumference of the metal foils 2, 3.

[0030] In the area between the circumferential edges 4, 5, the metal foils 2, 3 define a receiving space 6 filled with a gas, preferably helium. Other gases that can be used include air, CO2, N2, and the like, as well as gas mixtures, depending on the application of the cell separation element. To form the receiving space 6 (see also Fig. 2), the metal foils 2, 3 are plastically deformed accordingly, advantageously by a deep-drawing process.

[0031] As can be seen from Fig. 1, the metal foils 2, 3 are shaped such that they have obliquely running wall sections 7 to 10 adjoining the edges 4, 5, which, viewed in plan, have a trapezoidal outline and adjoin a central rectangular wall section 11. Alternatively, the transitions between the wall sections 7 to 10 could be so fluid that only a circumferential wall section is visible. The edges 4, 5 are also clearly visible. As clearly shown in Fig. 2, the wall sections 7 to 10 of the two metal foils 2, 3 are arranged at opposite angles to one another starting from the edge 4, 5. The central wall section 11 of the two metal foils 2, 3 is flat. The wall sections 11 extend parallel to one another depending on the position of the two metal foils 2, 3. As a result, the housing 1 has an essentially constant thickness 12 across its length and width.It decreases only towards the edges 4, 5 corresponding to the inclined wall sections 7 to 10. The edges 4, 5 are surrounded over most of their width on both sides by an elastically deformable cover part 14.

[0032] As a result, a uniform surface is provided by the central wall section 11, which in the assembled state causes a substantially homogeneous pressure distribution on the cells (not shown), which has a positive effect on the service life and the aging behavior.

[0033] Deviating from the described embodiment, the metal foils 2, 3 can have any other suitable spatial shape.

[0034] The metal foils 2, 3 have a relatively small thickness, preferably less than 1.2 mm. An advantageous thickness range is between approximately 0.3 mm and 0.7 mm. Such thin metal foils 2, 3 can be easily plastically deformed into the desired shape.

[0035] Aluminum or steel are examples of materials that could be used for the metal foils 2, 3. Alternatively, a suitable plastic, in particular a fiber-reinforced plastic, a fiber composite material, or even an elastic ceramic, is also conceivable.

[0036] As can be seen from Fig. 3, the connection between the adjacent edges 4, 5 is established by at least one material connection, in particular a welded connection 13. The welded connection 13 extends over the circumference of the edges 4, 5 of the metal foils 2, 3. Adhesive bonding is also conceivable for alternative materials instead of the metal foils 2, 3. A polyurethane adhesive is preferably used for this purpose.

[0037] The edges 4, 5 are surrounded on both sides by an elastically deformable cover part 14 over most of their width. It runs over the circumference of the edges 4, 5 and extends beyond the welded joint 13.

[0038] The cover part 14 has two sections 14a, 14b, of which section 14a is provided or attached to the edge 4, and section 14b is attached to the edge 5. Both sections 14a, 14b are advantageously of identical design and are preferably arranged mirror-symmetrically to each other. This has the advantage that the position of the cell separator does not need to be considered during installation.

[0039] In the illustrated embodiment, the two sections 14a, 14b are formed integrally with one another. For this purpose, the edges 4, 5 of the two metal foils 2, 3 are provided with openings 16 near the outer peripheral side 15, through which the material of the cover part 14 extends. These openings 16 are distributed over the circumference of the edges 4, 5, so that the two sections 14a, 14b are reliably connected to one another.

[0040] The sections 14a, 14b are attached to the edges 4, 5 in a suitable manner, for example by gluing, injection molding, vulcanizing, or the like. The edges 4, 5 extend outwardly beyond the cover part 14.

[0041] Deviating from the illustrated embodiment, the cover part 14 can also be designed to encompass the peripheral outer sides 15 of the edges 4, 5. In this case, the openings 16 are not absolutely necessary. Nevertheless, they can be provided in the edges 4, 5 with such a design. Deviating from the illustrated embodiment, the sections 14a, 14b can each be constructed as a single piece and placed only on the respective edge 4, 5.

[0042] Sections 14a, 14b are several times thicker than edges 4, 5 of metal foils 2, 3. Starting from the outer edge area of ​​metal foils 2, 3, sections 14a, 14b have a constant thickness in the exemplary embodiment. At a distance from the outer edge 15 and from the welded joint 13, sections 14a, 14b are thickened. Advantageously, the thickness of sections 14a, 14b increases steadily up to approximately the level of the welded joint 13, where sections 14a, 14b have their greatest thickness. Further inward, the thickness of sections 14a, 14b advantageously decreases again.

[0043] The sections 14a, 14b end at a distance from the receiving space 6. In this radially inner end region, the sections 14a, 14b are advantageously thicker than in the outer edge region of the metal foils 2, 3. The sections 14a, 14b adjoining the thickened regions 17a, 17b of the cover part 14 in the direction of the outer edge of the cell separation element are, for example, longer than the thickened regions 17a, 17b themselves.

[0044] Due to the described shape, the weld joint 13 is located in a thickened area 17a, 17b of the cover part 14. In the cross-section according to Fig. 3, the thickened areas 17a, 17b have roof-shaped outer sides 18a, 18b. The transition between the inclined sections of these outer sides 18a, 18b is advantageously curved.

[0045] The end face 19 of the cover part 14 facing the receiving space 6 of the housing 1 advantageously runs perpendicular to the edges 4, 5 of the metal foils 2, 3. The end face 19 transitions in a continuous curve into the roof-shaped outer sides 18a, 18b of the thickened regions 17a, 17b. The cover part 14 is advantageously made of an elastomer, for example a rubber or rubber-like material that can be reliably elastically deformed during use of the cell separation element. Examples of this are styrene-butadiene rubber (SBR), nitrile rubber (NBR), chloroprene rubber (CR), fluoropolymer rubber (FKM), butadiene rubber (BR), and ethylene-propylene-diene rubber (EPDM). This also ensures easy attachment of the cover part 14 to the edge 4, 5 of the housing 1.

[0046] The cover part 14 can also be made of polyurethane (PU), for example, which, like a rubber-like material, exhibits high elasticity, resilience, and excellent resistance to environmental influences. In particular, these materials offer the advantages of cost-effective production, easy attachment to the housing, and high resistance to mechanical stress.

[0047] Polyurethanes (PUR or PU) are polymeric materials synthesized through a polyaddition reaction between diols or polyols and polyisocyanates. The mechanical and thermal properties of polyurethanes can be modified by deliberately varying the degree of crosslinking and the monomers used, thus providing a wide range of materials. By specifically adjusting the chemical composition, thermosetting, thermoplastic, or elastomeric polyurethanes can be produced, which are suitable for a variety of applications.

[0048] The cover part 14 can be manufactured using various processing techniques, with the casting process (reaction injection molding, RIM) being a preferred method. In the casting process, the two main components, namely polyol and isocyanate, are transferred into a mixing chamber in a defined mixing ratio and intensively mixed there using a high-pressure or low-pressure mixer. The reactive mixture is then poured into a prepared mold, where polymerization begins and the material hardens within a few seconds to minutes.

[0049] The mold can be made of various materials, including aluminum, steel, or plastic-based materials such as epoxy resin molds. The choice of mold material depends on the desired surface finish, the production volume, and the mechanical stresses during the casting process.

[0050] The casting process enables targeted control of material properties through various process parameters, including:

[0051] Recipe variations: By adjusting the polyol and isocyanate components, the degree of hardness, elasticity and temperature resistance can be modified.

[0052] Use of catalysts: The addition of catalysts can shorten or lengthen the reaction time, thus optimizing the flowability of the PU material during mold filling.

[0053] Pressure and temperature control: The casting process can be carried out under atmospheric pressure or under vacuum. A vacuum casting process is particularly advantageous to avoid air inclusions and ensure a homogeneous material structure.

[0054] Post-curing: To achieve the final mechanical properties, thermal post-curing can be carried out in heated chambers or ovens at temperatures between 60 °C and 120 °C.

[0055] Alternatively, the cover part 14 can be manufactured from thermoplastic polyurethane (TPU) using an injection molding process. The material is introduced into an injection molding machine in granular form, melted, and injected into a mold under high pressure. This technique is particularly suitable for thin-walled, flexible components and allows for high precision and economical series production. Depending on the specific requirements, different Shore hardness levels can be realized, allowing the cover part to exhibit either greater dimensional stability or increased elasticity.

[0056] For applications requiring additional damping, the cover part 14 can be manufactured using a foaming process. Open-cell or closed-cell PU foam can be used, offering either a soft, flexible structure or high mechanical stability. Particularly advantageous is the use of integral foam, which combines a compact outer layer with a foamed inner structure, achieving both high strength and low weight.

[0057] To further optimize the mechanical properties and surface durability, the cover part 14 can be subjected to post-treatment. For example, a coating can be applied to increase abrasion or chemical resistance. Alternatively, a plasma or corona treatment can be performed to improve the adhesion properties for subsequent bonding. If necessary, the cover part can also be mechanically post-processed, for example, by cutting, punching, or milling, to achieve precise fits.

[0058] By carefully selecting the processing method, the cover part 14 can be optimally adapted to the specific requirements. While reaction molding (RIM) offers a high degree of freedom of shape for elastic components, injection molding enables cost-effective production of thin-walled, high-precision molded parts. If additional damping properties are required, the use of PU foams is recommended. Additional surface treatment can further improve long-term durability and mechanical performance.

[0059] The cover part 14 is thus characterized by high flexibility, mechanical strength, and adaptability. Depending on the chosen manufacturing method, targeted optimization can be achieved with regard to elasticity, dimensional stability, or damping properties, making the component ideal for applications requiring both mechanical and chemical resistance.

[0060] As already mentioned, the cell separation element comprises a housing 1 formed by two foils 2, 3. In the present embodiment, these foils are rectangular and are firmly and hermetically connected to one another along their edges 4, 5 to ensure a closed structure (see also Fig. 3).

[0061] Alternatively, the cell separation element can also comprise three or more films, creating several separate chambers within the housing (not shown). These additional films can differ in material, thickness, or mechanical properties from films 2 and 3 to enable targeted adaptation to different requirements.

[0062] The foils 2, 3 are preferably made of metal, in particular aluminum or an aluminum alloy, since this material exhibits high thermal conductivity, mechanical stability, and good chemical resistance to electrolytes. Alternatively, the foils can be made of other suitable materials, such as high-strength plastics, fiber-reinforced plastics, fiber composites, or elastic ceramics. These materials can be specifically selected to ensure certain properties such as flexibility, electrical insulation, or increased chemical resistance.

[0063] The edges 4, 5 can be connected by welding, gluing, or another suitable joining method. The width of the edge regions 4, 5, where the films abut each other, is advantageously constant over the entire circumference of the cell separation element to ensure uniform mechanical strength and reliable sealing.

[0064] To further improve mechanical stability and functionality, the cell separator can be provided with an additional outer layer. This coating is preferably made of polyurethane (PU) or another suitable elastic material. The coating can have a profile, for example, in the form of a wave pattern or a textured surface, to further optimize pressure distribution and improve thermal insulation properties.

[0065] The cell separation element therefore performs several technical functions:

[0066] It ensures even pressure distribution across adjacent cells to minimize mechanical stress. It acts as a thermal barrier to reduce heat transfer between neighboring cells and prevent local overheating. Through its hermetic seal, it contributes to the structural integrity of the cell assembly and protects against the ingress of moisture or foreign matter.

[0067] The cell separating element is inserted between two adjacent components 20, 21, i.e. cells, which rest on the cover part 14 running over the circumference (Fig. 4).

[0068] The battery cells or components lying next to and / or on top of each other

[0069] 20, 21 are pre-tensioned together with the cell separating element in a known manner to form the energy storage device (not shown) in order to produce a compact cell stack.

[0070] The spacing between these components 20, 21 is designed such that the thickened regions 17a, 17b of the cover part 14 are elastically compressed by the prestress of the cell stack in the assembled state. This situation is schematically illustrated in Fig. 4.

[0071] Due to the static elastic deformation of the assembly and the dynamic elastic deformation of the cell separation element caused by the swelling of the cells, pressure is exerted on the weld seam 13 via the thickened areas 17a, 17b, which ensures that the two edges 4, 5 in the area of ​​the weld seam 13 do not separate from each other and spread apart in this area.

[0072] This also ensures that the cell separator has a long service life and can perform its function perfectly. The cell separator is used to separate adjacent and / or stacked components 20, 21, particularly cells, which exhibit corresponding volume expansion (swelling) during charging / discharging in conjunction with heat generation. The cell separators provided between the cells ensure a temporally homogeneous pressure distribution on the cells, which has a positive effect on the service life and aging behavior of the cells.

[0073] A special area of ​​application for cell separation elements is, for example, energy storage devices formed from several battery cells lying next to and / or on top of one another, in particular pouch cells.

[0074] The cell separators serve to ensure a temporally homogeneous pressure distribution across the cells and also to electrically and thermally separate the battery cells within the energy storage system. Should one of the battery cells overheat during operation, for example, due to thermal runaway, the cell separator prevents neighboring battery cells from also overheating. Furthermore, the cell separators between the battery cells also serve as thermal insulation.

[0075] Since the cell separators are separate components, they can be easily inserted between the battery cells during assembly of the energy storage unit. The adjacent and / or stacked battery cells are firmly connected to each other in a conventional manner to form the energy storage unit, preferably pre-tensioned to create a compact cell stack.

[0076] Since the cover part is elastically deformable, i.e. compressible, the functionality of the cell separation element is guaranteed at all times in the manner described.

Claims

Claims 1. Cell separation element with a housing (1) in which a fluid is provided and which is formed by two film-like housing parts (2, 3) which are tightly connected to one another along their edge (4, 5), wherein at least one material-to-material connection (13) running over the length of the edge (4, 5) is provided in the edge region, characterized in that the material-to-material connection (13) is covered by an elastically deformable cover part (14) which is provided on the edge (4, 5) of the housing (1).

2. Cell separating element according to claim 1, characterized in that the cover part (14) extends at least close to the peripheral outer side (15) of the edge (4, 5) of the housing (1).

3. Cell separating element according to claim 1 or 2, characterized in that the cover part (14) is provided on the top and bottom sides of the edge (4, 5) of the housing (1).

4. Cell separation element according to claim 3, characterized in that the cover part (14) is formed in one piece.

5. Cell separating element according to claim 3 or 4, characterized in that the edge (4, 5) of the housing (1) has openings (16) distributed over its circumference, through which the material of the Cover part (14) extends.

6. Cell separation element according to one of claims 1 to 5, characterized in that the cover part (14) is thickened in the region of the material connection (13).

7. Cell separation element according to claim 6, characterized in that the outer side (18a, 18b) of the thickened region (17a, 17b) of the cover part (14) is roof-shaped.

8. Cell separating element according to claim 6 or 7, characterized in that a region (14a, 14b) of the cover part (14) extending from the thickened region (17a, 17b) in the direction of the peripheral outer side (15) has a constant thickness.

9. Cell separation element according to one of claims 1 to 8, characterized in that the housing parts (2, 3) are formed by metal foils.

10. Cell separating element according to one of claims 1 to 9, characterized in that the cover part (14) consists of rubber or rubber-like material. 11 . Cell separation element according to one of claims 1 to 10, characterized in that the cover part (14) comprises a polyurethane.

12. Cell separation element according to one of claims 1 to 11, characterized in that the material connection (13) comprises a polyurethane.

13. Cell separation element according to one of claims 1 to 12, characterized in that the cell separation element has an additional outer layer made of polyurethane.

14. Cell separation element according to one of claims 1 to 12, characterized in that the additional outer layer and / or the cover part (14) is provided with a coating.

15. Energy storage device with a cell separation element according to one of claims 1 to 14.

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