Sealing device for a battery cell with sealing element

Abstract

The invention relates to a closure device (1) for closing a battery cell (20) with a lid (2) having a recess (3) through which a liquid, in particular an electrolyte, can be filled into the battery cell (20), and with a closure lid (4) for closing the recess (3), wherein the recess (3) is designed as a stepped recess and has a stepped surface (3.11) recessed relative to the outside of the lid (2), wherein a sealing element (7) is arranged between the stepped surface (3.11) and the closure lid (4).

Description

[0001] The invention relates to a closure device for closing a battery cell with a lid having a recess through which a liquid, in particular an electrolyte, can be filled into the battery cell, and with a closure lid for closing the recess.

[0002] Battery cells are used in various technical fields and, for example, as energy storage devices for electric vehicles such as cars with hybrid or electric drives. Typically, several battery cells are used, which are electrically connected and function as a cohesive battery system.

[0003] The individual battery cells often have a cylindrical geometry and consist of a cylindrical housing, which is gas-tightly sealed at each end by sealing devices. The sealing device has a lid, and usually at least one of the two lids has a recess, mostly located in the center, through which an electrolyte can be added during the manufacturing of the battery cell.

[0004] After the electrolyte is added, a rubber ball is pressed into the recess, sealing it. In the next step, a cap is placed over the rubber ball and welded to the cap. The rubber ball primarily prevents contamination of the electrolyte by the weld. Without this additional protection, gases released during welding could penetrate into the battery cell and contaminate the electrolyte. While the use of the rubber ball for sealing has proven effective in the past, the manufacturing process is relatively complex. First, the rubber ball must be positioned in the recess, and then the cap must be attached and welded.

[0005] Based on this, the invention aims to provide a closure device that can be manufactured in a simpler manner, but which at the same time ensures a reliable seal. Furthermore, the invention aims to provide a corresponding manufacturing process.

[0006] The problem is solved in a closure device of the type mentioned above by the fact that the recess is designed as a stepped recess and has a stepped surface that is recessed from the outside of the cover, wherein a sealing element is arranged between the stepped surface and the closure cover.

[0007] This design allows for a highly reliable seal. Furthermore, it offers manufacturing advantages, as only the cap needs to be assembled as a single element for sealing, eliminating the step of pressing in a rubber ball with regard to the closure device and manufacturing process discussed above. Instead, the sealing element is positioned between the stepped surface and the cap, ensuring a seal only upon the cap's placement. It is unnecessary to create a seal before the cap is fitted and welded. The stepped surface can serve as a bearing surface for the sealing element, which is then compressed by the cap between the stepped surface and the cap to achieve the seal.

[0008] By being designed as a stepped recess, the recess can have different internal diameters. Advantageously, the recess has at least two different internal diameters, so that these different diameters divide the recess into two sections, as will be explained below. The stepped surface can be created by a change in diameter, so that the recess has a larger diameter on one side of the stepped surface, particularly above the stepped surface, and a smaller diameter on the other side, particularly below the stepped surface. The stepped surface can be arranged parallel to the outside and, in particular, also parallel to the inside of the lid. The stepped surface can be set back from the outside of the lid by between 1 and 20 mm, preferably between 3 and 15 mm, particularly preferably between 5 and 10 mm, and most preferably between 7 and 8 mm.Advantageously, the recess has only a single stepped surface.

[0009] With regard to the sealing element, it has proven advantageous for it to consist of a sealant or an adhesive, or to incorporate these components. A sealant can ensure a reliable seal when compressed by the cap. The sealant can be open-pored or closed-pored. A foam sealant, particularly polyurethane (PU) foam, is advantageous. Other materials can also be used. The sealant can be in the form of a ring, especially an O-ring, and have a substantially circular cross-section. However, a flattened cross-section, such as a semicircle, or other cross-sections are also possible. To ensure a secure hold, the sealant can be bonded to the step surface. The sealant can be pre-mounted on the step surface.The sealant is pre-applied to the cell. This simplifies the actual sealing process and prevents the cap from slipping. The sealant can therefore already be applied when the battery cell is filled with liquid. After filling, the cap can be placed on the cell and then welded to the lid. The sealing process can thus be carried out very quickly.

[0010] Designing the component as an adhesive, or at least incorporating adhesive, can also lead to a reliable seal. In this case, the closure cap can be bonded to the lid or the step surface via the adhesive. This achieves a reliable seal and simultaneously pre-fixes the closure cap, allowing it to be securely welded in a subsequent step. The adhesive

[0011] With regard to the geometric design of the sealing element, it has proven advantageous for it to be designed as a sealing bead. The sealing element can thus be positioned within the areas to be sealed, which can reduce the overall material usage. This will be explained in more detail below with regard to the design of the cover and the arrangement of the sealing element. Advantageously, the sealing element is designed as a closed profile, so that, for example, a bore or the second recess area explained below can be sealed by the sealing element forming a closed circumferential border around the corresponding opening in the stepped surface.

[0012] According to an alternative embodiment, the sealing element is designed as an adhesive film. The adhesive film can have a flat geometry and be applied to the step surface. Geometrically, the adhesive film can be circular. However, an angular, particularly rectangular, or other geometric shape is also possible. It is important that the adhesive film covers the opening of the second recess area in the step surface, ensuring a reliable seal. To guarantee reliable coverage, the adhesive film can be electrolyte-resistant. The adhesive film can be used to immovably connect the closure cover to the step surface, preventing unwanted relative movement, especially during the welding of the closure cover to the lid.

[0013] Furthermore, it has proven advantageous for the lid and the closure cap to be arranged flush with each other. This design ensures that the closure cap does not protrude from the lid after connection. Instead, the closure cap can be completely within the contour of the lid. The closure cap and the lid can each have an outer and an inner surface, with the respective inner surfaces facing the interior of the battery cell and the outer surfaces facing away from the battery cell or its interior, respectively. To achieve the flush arrangement, the respective outer surfaces can lie in a common plane. The thickness of the closure cap is advantageously dimensioned so that it rests on the stepped surface while simultaneously being flush with the outer surface of the lid.The thickness of the lid advantageously corresponds to the offset of the stepped surface relative to the outside of the lid.

[0014] According to an advantageous embodiment of the invention, the closure cap and the lid are made of the same material, in particular an aluminum alloy. When both elements are made of the same materials, they can be welded together with a material-pure weld, which generally results in high strength. Aluminum or an aluminum alloy has proven to be particularly advantageous, among other reasons, due to its light weight, high mechanical stability, and good corrosion resistance.

[0015] Regarding the arrangement of the end cap and the lid, it has proven advantageous for both to share a common central axis. Both the end cap and the lid can be designed as solids of revolution, and the central axis can correspond to their respective axes of symmetry. Due to the shared central axes—that is, the central axis of the lid coinciding with the central axis of the end cap—the two elements are arranged concentrically. The recess can thus be located centrally in the lid, and the central axis can accordingly extend centrally through the recess. Overall, both the lid and the end cap can therefore have a cylindrical geometry. Furthermore, the shared central axis can also correspond to the central axis or axis of symmetry of the battery cell.This means that the battery cell can have a cylindrical casing, which is closed at each end by a locking device, and the casing can be arranged concentrically to the central axis.

[0016] According to an advantageous embodiment, the recess is designed to have a first recess area located axially outside the central axis of the lid and a second recess area located axially inside the central axis of the lid. The first recess area may have a larger diameter than the second recess area. The two recess areas may be directly connected and merge seamlessly. The recess areas may be arranged one behind the other in the axial direction. The first recess area may extend inwards from the outside of the lid, and the second recess area may extend outwards from the inside of the lid.

[0017] The first recess area can have a side surface extending circumferentially in the axial direction towards the central axis of the cover, and the closure cover can contact this side surface, particularly circumferentially. Similarly, the second recess area can also have a side surface extending circumferentially in the axial direction towards the central axis of the cover, and this side surface can also be contacted by the closure cover, particularly circumferentially. It can be provided that a press fit exists between the side surface of the first recess area and / or the side surface of the second recess area and the closure cover in order to secure the closure cover and seal the recess circumferentially. The side surfaces of the recess can be designed as inner surfaces.

[0018] The side surfaces of the respective recess areas can be cylindrical or conical. Advantageously, the side surface of the second recess area is conical and the side surface of the first recess area is cylindrical. The conical design allows for a press-fit connection when the closure cap is pressed in, as the closure cap is compressed by the conical design during insertion. For shrink-fitting, exclusively cylindrical side surfaces can also be used. The cone angle of the conical side surface(s) can advantageously be in the range of 1 to 10 degrees, preferably in the range of 3 to 7 degrees, and particularly preferably in the range of 4 to 6 degrees. In particular, the cone angle is essentially 5 degrees.

[0019] Regarding the closure cover, a monolithic design has proven advantageous. This allows the cover to be both robust and easy to manufacture. Furthermore, a monolithic closure cover facilitates simple assembly of the cover or easy closure of the recess, as it eliminates the need to assemble multiple individual, loose components.

[0020] Regarding the cap, it has proven advantageous for it to be sintered or pressure-cast. These methods allow for relatively simple production of the cap. Alternatively, the cap can also be manufactured using a forming process. For example, it can be produced by forging, particularly by die forging.

[0021] To ensure a reliable hold for the sealing element, it has proven advantageous for the lid to have a groove for its placement. The groove holds the sealing element in position, preventing it from slipping. The groove can be geometrically adapted to the geometry of the sealing element. It can extend axially from the stepped surface. The groove can be deep enough that the sealing element protrudes slightly axially from the groove and thus also from the stepped surface. This ensures that the sealing element can compress the lid when the cap is placed on the lid. The sealing element can be elastically pressed or formed into the groove. Advantageously, the groove is arranged concentrically to the central axis, so that it surrounds the central axis.The groove can thus have an annular geometry in a top view, allowing the sealing element to be arranged circumferentially within the groove to ensure a reliable seal. For manufacturing, the groove can be milled into the step surface, for example. The groove can surround the second recess or the opening of the second recess area located in the step surface at a constant circumferential distance.

[0022] According to an alternative embodiment, the groove can also be arranged on the cap side, so that the cap can have a groove. Specifically, the cap can have a groove on its side facing the stepped surface. The sealing element can then be arranged in this groove of the cap and come into contact with the stepped surface when the cap is placed on the cap. To create the sealing effect, the sealing element can then be elastically deformed by the stepped surface within the groove. The groove can be arranged concentrically to the central axis of the cap and extend axially into the cap in the manner of a ring arranged concentrically to the central axis. For further details regarding the design and arrangement of the groove, please refer to the above. These descriptions also apply analogously to the arrangement on the cap.

[0023] According to an advantageous embodiment of the invention, a support projection is provided for the sealing element. This support projection can extend axially beyond the stepped surface, allowing the sealing element to be positioned slightly higher than the stepped surface. This design enables the sealing element to have a smaller diameter while maintaining the same surface pressure between the sealing element and the closure cap. Structurally, the support projection can be ribbed. To prevent the sealing element from slipping, it can be attached to the support projection, particularly via an adhesive layer. In a top view, the support projection can have an annular geometry, thus circumferentially surrounding the second recess or the opening of the second recess located in the stepped surface.Therefore, the support projection can be arranged concentrically to the central axis of the lid. Alternatively, the support projection can be located on the closure lid. Furthermore, the support projection can be designed to correspond to a groove, in particular a groove on the closure lid side. This design allows the support projection to ensure that the sealing element is pressed into the groove or elastically deformed into it when the closure lid is placed on the lid.

[0024] According to an advantageous embodiment of the invention, the closure cap is cylindrical. Such a closure cap is very easy to manufacture. The axial extent of the closure cap can be significantly less than the radial extent, so that the closure cap can have a disc-shaped geometry overall. The closure cap can have a side surface arranged concentrically to its central axis. This side surface can contact the side surface of the cap, particularly around its circumference. Due to its cylindrical shape, the outer surface of the closure cap can have the same, or at least substantially the same, size or diameter as the inner surface of the closure cap. The closure cap can be adapted to the design of the recess and, in particular, to the design of the first recess area.The closure cover can completely fill the first recess area, particularly its entire volume. This design allows for a zero gap between the recess area and the closure cover, enabling a very simple welded connection. The radial dimensions of the first recess area and the closure cover can be identical. The same applies to the radial dimensions.

[0025] Furthermore, the closure cap can be press-fitted to the lid. Such a press fit results in an even more reliable seal, as the press fit itself provides a certain degree of tightness.

[0026] In this context, a conical design for the closure cap has proven advantageous. It is particularly beneficial if the closure cap is conical when the recess or the first recess area is cylindrical. However, the design can also be reversed, meaning that the side surface of the closure cap can be cylindrical and the side surface of the cap or the first recess area can be conical. Thus, it can be provided that at least one conical side surface interacts with a cylindrical side surface to achieve a press fit. The closure cap can then be pressed into the cap or the recess by a force acting in the direction of the central axis.The conical shape of at least one side surface causes a slight, particularly elastic and / or plastic, deformation of the cylindrical side surface, and this deformation creates a surface pressure between the two side walls. Alternatively, instead of pressing the cap in, it can also be designed so that the closure cap is shrunk into the lid or the recess. A press fit can also be achieved in this way.

[0027] Furthermore, the closure cap may also have a first closure area located axially outside the center of the cap and a second closure area located axially inside the center of the cap. The first closure area may have a larger diameter than the second. The two closure areas may be monolithically connected. The first closure area may have a disc-shaped geometry, and the second closure area may have a pin-shaped geometry. The second closure area may project axially beyond the first. In a side cross-sectional view, the closure cap may thus have a T-shaped geometry.The two closure areas can each have a side surface, which can be arranged concentrically to the central axis of the closure lid and which can extend axially with respect to the central axis. The two side surfaces can be designed as outer surfaces.

[0028] It may be provided that at least one of the closure areas is conical. It is advantageous for one of the closure areas to be conical if the recess areas are cylindrical. Thus, it may be provided that at least one conical side surface interacts with a cylindrical side surface to achieve a press fit. If at least one recess area is already conical, or if the closure cap is to be press-fitted to the lid using a shrink-fit process, both closure areas or their respective side surfaces may be cylindrical. The second closure area may project into the second recess area.

[0029] With regard to the aforementioned task, a method for manufacturing a closure device is further proposed, which allows the production of a closure device of the type described above. The following steps are provided: - Providing a lid blank; - Cutting out, in particular punching, a closure lid blank from the lid blank; - Inserting the blank closure cap into a forming tool, in particular a die; - Forming the blank cap into a cap.

[0030] The advantages already described with regard to the closure device result. The lid blank can initially be a semi-finished product, particularly one with a cylindrical shape. By separating the closure lid blank from the lid blank, material costs can be significantly reduced, as the closure lid blank does not need to be provided separately but is instead generated as a byproduct. This is because the recess in the lid blank can be produced or at least pre-formed simultaneously during the separation process. Thus, a separate step for producing or pre-forming the recess in the lid blank can be eliminated. It is advantageous if the separation process is chipless, so that no material is lost. In this respect, a stamping process has proven particularly beneficial. However, a drilling process, for example using a core drill, can also be employed.

[0031] After the closure lid is cut out of the lid blank, it is not necessarily required that the lid immediately has its final geometric shape. Since a cylindrical area can be removed during the cutting process, but the resulting recess may be a stepped recess, it can be reshaped into a stepped recess in a subsequent step. Alternatively, the lid blank can be prepared accordingly beforehand. For example, the first recess area can already be incorporated into the lid blank, and the second recess area can then be created by cutting it out.

[0032] After cutting, the resulting cap blank is placed in a forming tool, in particular a die, and then formed within the forming tool. A punch may be used for this purpose, which presses the cap blank into the forming tool or die, thus forming it into the cap.

[0033] Furthermore, the method may include the step of cutting a groove into the lid or the closure cap and inserting a sealing element into the corresponding groove. If no groove is provided or is not intended to be provided, the method may include applying a sealing element, in particular gluing a sealing element, to the stepped surface.

[0034] Furthermore, with regard to the aforementioned task of manufacturing the closure device, the following steps are proposed: - Inserting the lid into the recess; - Welding, especially laser welding, of the closure cap to the lid.

[0035] These steps can be performed with or without the steps described above. The advantages already described with regard to the closure device result. By inserting the closure cap into the lid or the recess, the recess is closed. The sealing element is then compressed regardless of its position, thus ensuring a tight seal. The closure cap can be inserted into the lid or the recess. Alternatively, it can also be pressed in or shrunk in place if a press fit with the lid is desired, as explained above.

[0036] In the next step, the end cap is welded to the end cap. This creates a gas-tight seal around the battery cell. The weld seam runs along the gap between the end cap and the end cap and can be circular. The end cap and end cap can be welded from the outside. Laser welding has proven particularly effective, as it is characterized not only by high precision but also by its suitability for automation.

[0037] Furthermore, it may be provided that the sealing element is positioned before the lid is inserted, either in a groove or on the step surface or the support projection.

[0038] Further details and advantages of the invention will be explained in more detail below with reference to the accompanying schematic drawings of various embodiments. These drawings show: Fig. 1 a schematic, cutaway side view of a locking device for a battery cell according to a first embodiment; Fig. 2a a schematic, cutaway side view of a lid of a closure device for a battery cell according to a further embodiment; Fig. 2b a schematic, cutaway side view of the locking device according to Fig. 2a; Fig. 3 two schematic, perspective representations of a tool for manufacturing a closure lid; Fig. 4 A schematic, cutaway side view of a locking device for a battery cell with an insulating device Fig. 5 a schematic, cutaway side view of a closure device with a sealing plug for a battery cell; Fig. 6 a schematic, cutaway side view of a closure device with a sealing element resting on a stepped surface for a battery cell; Fig. 7 a schematic, cutaway side view of a closure device with a sealing element arranged in a groove of the closure cover for a battery cell; Fig. 8 a schematic, cutaway side view of a closure device with a sealing element arranged in a groove of the closure cover for a battery cell; Fig. 9 a schematic, cutaway side view of a closure device with an adhesive film; Fig. 10 A schematic side view of a battery cell with a cylindrical casing which is closed at both ends by a locking device.

[0039] The presentation of Fig. Figure 1 shows a schematic, cutaway side view of a locking device 1, with which a device shown in the illustration of the Fig. 10. The battery cell 20, which can be schematically identified, can be closed. The battery cell 20 is cylindrical and has a cylindrical casing 21, which is closed at the top and bottom by a locking device 1. Fig. 1, Fig. Figures 2 and 4 to 9 show various embodiments of a corresponding locking device 1, with which one side of the housing 21 can be closed. The other side of the housing 21 can also be closed by a locking device 1 shown in the illustrations. Alternatively, the other side can also be closed by a simple circular disc. The individual features of the various locking devices 1, which are described in more detail below, can be partially combined with one another, so that the description of the individual embodiments should not be considered exhaustive. Rather, the description is intended to focus specifically on the differences between the various embodiments.

[0040] The presentation of Fig. Figure 1 shows a section of a flat, essentially disc-shaped cover 2, which is gas-tightly connected around its circumference to the cylindrical housing 21 of the battery cell 20. The cover 2 has a recess 3 in its center, providing access to the interior of the battery cell 20. An electrolyte can be added through this recess 3 during the manufacturing process of the battery cell 20. After the electrolyte has been added, the recess 3 must be sealed gas-tight. A sealing cap 4 is provided for this purpose, as shown in the illustration. Fig. 1 is designed as a flat cylindrical disc adapted to the recess 3. Once the closure cover 4 has been positioned accordingly, it is joined to the cover 2 by means of a laser welding process. The laser beam is moved in an essentially circular path along the seam between cover 2 and closure cover 4, so that the cover 2 and the closure cover 4 are firmly and inseparably joined together. The battery cell 20 is then gas-tightly sealed by the closure device 1.

[0041] The lid 2 as well as the smaller closure lid 4 each have an outer surface 2.1, 4.1 and an inner surface 2.2, 4.2 arranged parallel to the outer surface 2.1, 4.1, wherein the respective inner surfaces 2.2, 4.2 face the interior of the battery cell 20 and the outer surfaces 2.1, 4.1 face away from the interior of the battery cell 20.

[0042] Furthermore, the recess 3 is not a cylindrical through bore with a constant diameter, but rather is designed as a stepped recess that allows the recess 3 to be sealed by the closure cover 4 and simultaneously ensures that the closure cover 4 is positioned within the contour of the cover 2 and does not protrude upwards relative to the cover 2 or to the outer surface 2.1 of the cover 2. The design of the recess 3 is also shown in the illustration of the Fig. 2a can be seen, in which the closure lid 4 is not shown.

[0043] Due to its design as a stepped recess, the recess 3 has a stepped surface 3.11 that is set back from the outer surface 2.1 of the cover 2, thus creating a substantially cylindrical receiving space for the closure cover 4. This receiving space is also referred to as the first or outer recess area 3.1 and is adapted to the closure cover 4 in both radial and axial dimensions, so that the closure cover 4 does not protrude from the outer surface 2.1 of the cover 2. A smaller, also cylindrical, second recess area 3.2 adjoins the first recess area 3.1 in the axial direction, which is also shown, for example, in the illustration of the Fig. 2a can be seen. The two recess areas 3.1, 3.2 are each symmetrical about the central axis M and together they form the recess 3, which in cross-section resembles a T.

[0044] The design according to Fig. Figure 1 shows a disc-shaped closure cover 4 that almost completely fills the recess 3.1. The inner surface 4.2 of the closure cover 4 rests on the stepped surface 3.11, so that the closure cover 4 covers the second recess 3.1, or rather, the circular opening of the second recess 3.1. If the closure cover 4 were simply inserted into the first recess 3.1, it would not provide a sufficient seal, and gases generated during the welding process could enter the interior of the battery cell 20 and contaminate the electrolyte. Therefore, it is essential to ensure that a reliable seal of the recess 3 is established before the closure cover 4 is welded to the cover 2, preventing gases from entering the interior of the battery cell 20 through the recess 3.

[0045] The design according to Fig. Figure 1 provides for a press fit between the closure cap 4 and the cover 2. This is achieved by the closure cap 4, or rather its circumferential side surface 4.3, not being exactly cylindrical, but slightly conical. At its axially lower end, the closure cap 4 is therefore slightly smaller than the recess 3, or rather the first recess area 3.1, and slightly larger at its axially upper end. When the closure cap 4 is placed on the cover 2 without force, it initially protrudes slightly in the axial direction from the surface, or outer surface 2.1, of the cover 2. Only by applying an axial pressing force can the closure cap 4 be fully pressed into the recess 3 until its inner surface 4.2 rests completely on the stepped surface 3.11. Because the closure cap 4 is slightly conical, it is deformed by the cover 2 during the pressing process.This deformation creates a circumferential and axial force acting from the sealing cap 4 onto the cover 2. This deformation ensures a reliable seal of the recess 3 by the sealing cap 4, preventing gases generated during welding from penetrating into the interior of the battery cell 20. The sealing effect is thus achieved entirely by the press fit between the sealing cap 4 and the cover 2.

[0046] Although it was described above that the side surface 3.12 of the closure cover 4, or of the first recess area 3.1, is cylindrical and thus concentric to the central axis M, and the side surface 4.3 of the closure cover 4 is conical, this can also be reversed. That is, the side surface 3.12 of the recess 3 can be slightly conical, and the side surface 4.3 of the closure cover 4 can be cylindrical. In both cases, pressing in the closure cover 4 results in deformation and a press fit, thus creating a seal even before the final welding of the closure cover 4 to the cover 2. Therefore, in this embodiment, it is important that at least one side surface 3.12, 4.3 is conical in order to achieve deformation and thus a sealing press fit during pressing in.

[0047] The embodiment according to the Fig. 2a and Fig. 2b now differs from the embodiment of the Fig. 1 by a slightly different design of the closure cover 4 as well as by a different method for connecting the closure cover 4 to the cover 2. First, the closure cover 4 is designed as a stepped cover. That is, the disc-shaped closure cover 4 is attached according to Fig. 1. Concentric to the central axis M of the closure lid 4, a second disc-shaped area projecting in the axial direction is formed, so that the T-shaped geometry in cross-section is created, which is shown in the illustration of the Fig. 2b can be seen. According to the representation of the Fig. 2b The larger outer area is referred to as the first closure area 5 and the smaller inner area as the second closure area 6. The first closure area 5 is further adapted to the geometry of the first recess area 3.1 and the second closure area 6 to the geometry of the second recess area 3.2. That is, the diameter of the second closure area 6 essentially corresponds to the diameter of the second recess area 3.2, so that the second closure area 6 lies almost entirely against the side surface of the second recess area 3.2.

[0048] The second closure area 6 does not completely fill the second recess area 3.2, but only extends a short distance into the second recess area 3.2. This is also shown in the following illustration of the Fig. 3 the manufacturing process of the closure lid described in more detail 4.

[0049] Even in the design according to the presentation of the Fig. 2a and Fig. In 2b, the closure cap 4 is press-fitted to the lid 2. However, in this embodiment, the closure cap 4 is not pressed into the recess 3 or the lid 2 with considerable force, but rather it is shrunk in. For this purpose, the closure cap 4 is cooled and / or the lid 2 is heated. Due to the temperature-induced expansion or contraction, the closure cap 4 can be placed in the recess 3 without requiring much force. When the temperatures of the closure cap 4 and the lid 2 then approach each other again, the closure cap 4 expands relative to the lid 2, so that it is pressed axially against the side surfaces of the lid 2 or the recess 3. This creates a sometimes very strong press fit between the closure cap 4 and the lid 2, which ensures a reliable seal of the recess 3.Since no large pressing forces acting in the axial direction are required during shrinking, the side walls in this design can be purely cylindrical rather than conical.

[0050] Furthermore, it may also be provided that the side surface of the second closure area 6 is conical or that the corresponding side surface of the second recess area 3.2 is conical. In the case of a press connection by pressing in, the sealing effect can thus be realized both in the area of ​​the first recess area 3.1 and in the area of ​​the second recess area 3.2.

[0051] The presentation of Fig. Figure 3 now shows a schematic, cutaway side view of a tool consisting of a die 31 and a punch 32, which is movable axially relative to the die 31 and is shown with dashed lines to better illustrate the area under the punch 32. In the right-hand illustration of the Fig. In the die 31, a blank cap 10, which has a cylindrical geometry and is made of solid material, is inserted. This blank cap 10 represents the starting material for manufacturing the cap 4. To produce the cap 4 from the blank cap 10, the punch 32 is moved downwards with considerable force towards the die 31. This plastically deforms the blank cap 10 and presses it into the die 31. The die 31 acts as a mold, so that after the punch 32 moves into position, the blank cap 10 conforms to the shape of the die 31. The cap 4 formed from the blank cap 4 is then shown in the right-hand illustration. Fig. 3 to recognize. It is evident that the representation of the Fig. 3 shown closure lids 4 the closure lid 4 the Fig. 2b corresponds and the shape of the matrix 31 corresponds to a negative of the closure lid 4 to be produced. However, the closure lid 4 can also be produced according to Fig. 1. Produce in the appropriate manner. However, this would require the use of a differently designed die 31.

[0052] The cylindrical cap blank 10 was produced by stamping it out of a disc-shaped cap blank that has the outer contours of the cap 2. For this purpose, a section with a circular base is punched out of the center of the cap blank using a stamping tool, resulting in the cylindrical cap blank 10. The hole remaining in the cap blank is the recess 3, or part of it. Therefore, the diameter of the cap blank 10 can also correspond to the diameter of the second recess area 3.2. After the cap blank 10 has been stamped out of the cap blank, the cap blank can be further processed in subsequent steps, in particular to create the geometric, stepped design of the recess 3.Overall, the use of the part punched out of lid 2 as the starting product for the closure lid 4 significantly reduces the material costs.

[0053] The presentation of Fig. Figure 4 shows a sectional view of the upper part of a battery cell 20 and thus a closure device 1. The cover 2 and the recess 3 are essentially designed in the same way as in the embodiments described above, so reference is made to the above regarding their design. On the inside 2.2 of the cover 2, an insulating device 9 made of plastic is provided, which covers the inside 2.2 of the cover 2. The insulating device 9 has a bore 9.1 concentric to the recess 3, so that the central axis M runs not only centrally through the cover 2 and the closure cover 4, but also through the bore 9.1 of the insulating device 9. Furthermore, it can be seen from the illustration of the Fig. 4 to recognize that the insulating device 9 not only rests against the inside 2.2 of the cover 2, but the insulating device 9 extends into the second recess area 3.2 and thus also covers the side surface of the second recess area 3.2.

[0054] As can be seen in a comparison of the representation of the Fig. 4 with the representations of the Fig. 1, Fig. 2 to Fig. As can be seen in Figure 3, the lower, second closure area 6 is shown in the illustration of the Fig. 4 is designed to be somewhat smaller than in the preceding embodiments. This means that the diameter of the second closure area 6 is somewhat smaller. The second closure area 6 therefore does not contact the side surface of the second recess area 3.2 directly as in the preceding embodiments, but rather it contacts the side surface of the bore 9.1 of the insulating device 9. The insulating device 9 is thus located between the second closure area 6 and the second recess area 3.2.

[0055] In this embodiment, the sealing effect can be achieved through contact between the insulating device 9 and the closure cover 4, particularly since the insulating device 9 is made of plastic and the closure cover 4, as well as the lid 2, are made of metal. Analogous to the embodiments described above, at least one of the adjacent side surfaces can be conical. Furthermore, a press fit between the closure cover 4 and the lid 2 can also be present in this embodiment.

[0056] In the exemplary embodiments shown in the illustrations of the Fig. 5, Fig. 6, Fig. 7 to Fig. As shown in Figure 8, a seal is provided in each case to seal the recess 3, preventing gases from entering the interior of the battery cell 20. However, a press fit between the closure cover 4 and the cover 2 can also be provided for additional sealing, as described above.

[0057] In the representation of the Fig. In the embodiment shown in Figure 5, the closure cover 4 has a sealing plug 5.1, which is arranged on the side of the first closure area 5 facing the interior of the battery cell 20 and has a substantially cylindrical geometry. This sealing plug 5.1 rests against the side surface of the second recess area 3.2, thus protecting the electrolyte from unwanted gas ingress. When the closure cover 4 is positioned or pressed in, the sealing plug 5.1 is slightly deformed, particularly in its elastic range, so that it bears flat against the side surface of the recess 3 or the second recess area 3.2, thereby creating a seal in this area. In this configuration, a press fit exists between the sealing plug 5.1 and the cover 2 or the second recess area 3.2.

[0058] To connect the sealing plug 5.1 to the first closure area 5, a pin-shaped injection area 6.2 is formed on the inside 4.1 of the first closure area 5. This ensures a reliable hold for the plastic sealing plug 6.1. The injection area 6.2 projects axially from the first closure area 5, thus increasing the surface area and improving the adhesion of the sealing plug 6.1. In the embodiments described above, the sealing plug 6.1, possibly in combination with the injection area 6.2, therefore functions as the second closure area 6.

[0059] Furthermore, the presentation of Fig. It can be seen in Figure 5 that the outer surface 4.1 of the closure cap 4 is not exactly in the same plane as the outer surface 2.1 of the lid 2. This may simplify the welding of the closure cap 4 to the lid 2, but it is not absolutely necessary. That is, the two outer surfaces 2.1, 4.1 can also lie in the same plane, as is the case in the preceding embodiments.

[0060] The representation of Fig. The embodiment shown in section 6 differs from the embodiment shown in section 6. Fig. 1 essentially by the fact that a sealing element 7 is arranged between the closure cover 4 and the cover 2. Specifically, the sealing element 7 is glued onto the stepped surface 3.11 and surrounds the second recess area 3.2, or rather the circular opening of the second recess area 3.2 that terminates in the stepped surface 3.11. The sealing element 7 is thus designed as a sealing ring and is compressed by the closure cover 4 to achieve the sealing effect, so that a sealing effect between the inside 4.2 of the closure cover 4 and the stepped surface 3.11 is achieved, sealing the recess 3. This is shown in the illustration of the Fig. As can be seen in Figure 6, the sealing element 7 in this embodiment has a semicircular cross-section, so that the sealing element 7 rests flat on the cover 2 or on the stepped surface 3.11, ensuring good adhesion. Although the closure cover 4 in this and also in the other embodiments according to the Fig. 7 and Fig. 8 has no step and is not designed as a stepped lid but as a disc-shaped lid, it is nevertheless possible to alternatively use the closure lid 4 according to Fig. to use 2b.

[0061] The exemplary embodiment according to Fig. 7 now differs essentially from the embodiment of the Fig. 6 by the fact that the sealing element 7 extends into the closure cover 4. For this purpose, the closure cover 4 has a groove 3.3 on its inner surface 4.2, arranged concentrically to the central axis M, in which the sealing element 7 is arranged, at least partially. Since the sealing element 7 extends into the closure cover 4, the latter can be used in a different configuration compared to the embodiment according to Fig. 6 be somewhat thicker or have a greater axial extension. The inner surface 4.2 of the closure cover 4 thus rests almost exactly on the stepped surface 3.11, or the gap is very small. Nevertheless, it is ensured that the sealing element 7 is elastically deformed to guarantee a sealing effect. Except for the fixing in the annular groove 3.3, which ensures a predefined positioning of the sealing element 7, reference is made to the above regarding the design and arrangement of the sealing element 7. During assembly, the sealing element 7 can be pre-assembled in the closure cover 4, so that the closure cover 4 can then be positioned together with the sealing element 7 in the recess 3. It is also possible for the sealing element 7 to be, for example, glued into the groove 3.3 or frictionally secured in the groove 3.3.

[0062] The representation of Fig. The embodiment shown in section 8 differs from the embodiment according to the Fig. 7 essentially by the arrangement of the groove 3.3. Because in the example according to Fig. 7 is the groove 3.3 on the lid side and in the example according to Fig. 8 The groove 3.3 is located on the lid side or in the stepped surface 3.11. The groove 3.3 thus extends axially into the lid 2, enclosing the opening of the second recess area 3.2, however analogous to the illustrations of the Fig. 6 and Fig. 7 illustrated examples.

[0063] The sealing element 7 can be positioned in the lid 2 before the closure cover 4 is positioned. When the closure cover 4 is put on, its inner surface 4.2 compresses the sealing element 7, thereby creating a seal. The sealing element 7 is pressed into the groove 3.3 and simultaneously presses against the inner surface 4.2 of the closure cover 4.

[0064] In the representation of the Fig.In the embodiment shown in Figure 9, a flat sealing element 7 is provided between the closure cover 4 and the stepped surface 3.11. This sealing element is designed as an adhesive film 8 and is indicated by a thick black line in the cross-sectional view shown. This adhesive film 8 can be pre-applied to the inside 4.2 of the closure cover 4, and then the closure cover 4 can be glued into the recess 3. The adhesive film 8 thus ensures an adhesive bond between the closure cover 4 and the lid 2. Furthermore, the adhesive film 8 covers the opening of the second recess area 3.2 completely, which, in combination with the flat adhesion to the stepped surface 3.11, ensures a reliable and gas-tight seal of the interior of the battery cell 20. It is also possible for the closure cover 4 to be press-fitted to the lid 2. However, due to the sealing effect of the adhesive film 8, this is not strictly necessary.

[0065] Overall, the various configurations described above allow for a reliable seal of the recess 3, so that after the sealing cap 4 is positioned in the recess 3 and welded to the cover 2, no gases can penetrate through the recess 3 into the interior of the battery cell 20. Contamination of the electrolyte is thus prevented. REFERENCE MARK LIST 1 locking device 2 lids 2.1 Outside 2.2 Inside 3 Exclusion 3.1 First exclusion area 3.11 Step surface 3.12 Side surface 3.2 second exclusion area 3.3 Nut 4 sealing caps 4.1 Outside 4.2 Inside 4.3 Side surface 5 first closure area 6 second closure area 6.1 Sealing plug 6.2 Injection area 7 Sealing element 8 adhesive film 9 Insulation device 9.1 Drilling 10 blank closure caps 20 battery cells 21 cases 31 die 32 stamps M Central axis

Claims

A closure device for closing a battery cell (20) with a lid (2) having a recess (3) through which a liquid, in particular an electrolyte, can be filled into the battery cell (20), and with a closure lid (4) for closing the recess (3), characterized in that the recess (3) is designed as a stepped recess and has a stepped surface (3.11) recessed relative to the outside of the lid (2), wherein a sealing element (7) is arranged between the stepped surface (3.11) and the closure lid (4). Closure device according to claim 1, characterized in that the sealing element (7) consists of a sealing plastic or an adhesive. A sealing device according to one of claims 1 or 2, characterized in that the sealing element (7) is designed as a sealing bead. Closure device according to one of claims 1 or 2, characterized in that the sealing element (7) is designed as an adhesive film (8). Closure device according to one of the preceding claims, characterized in that the sealing element (7) is arranged on the step surface (3.11). Closure device according to one of the preceding claims, characterized in that the lid (2) has a groove (3.3) for arranging the sealing element (7). Closure device according to one of the preceding claims, characterized in that the closure cover (4) has a groove (3.3) for arranging the sealing element (7). Closure device according to one of the preceding claims, characterized in that the lid (2) and the closure lid (4) are arranged flush with each other. Closure device according to one of the preceding claims, characterized in that the lid (2) and the closure lid (3) have a common central axis (M). A locking device according to one of the preceding claims, characterized in that the recess (3) has a first recess area (3.1) arranged axially outside with respect to the central axis of the cover (2) and a second recess area (3.2) arranged axially inside with respect to the central axis of the cover (2), wherein the first recess area (3.1) has a larger diameter than the second recess area (3.2). Closure device according to claim 10, characterized in that the outer recess area (3.1) has a side surface (3.12) extending axially to the central axis (M) of the cover (2), wherein the closure cover (4) contacts the side surface (3.12) circumferentially. A closure device according to one of the preceding claims, characterized in that the closure cover (4) is cylindrical or in that the closure cover (4) has a first closure area (5) arranged axially outside with respect to the central axis of the closure cover (4) and a second closure area (6) arranged axially inside with respect to the central axis of the closure cover (4), wherein the first closure area (5) has a larger diameter than the second closure area (6). Closure device according to one of the preceding claims, characterized in that the closure lid (4) is press-fitted to the lid (2). Method for manufacturing a closure device (1) according to one of claims 1 to 13, characterized by the following steps: - Providing a lid blank; - Cutting out, in particular punching, a closure lid blank (10) from the lid blank; - Inserting the closure lid blank (10) into a forming tool, in particular a die (31); - Forming the closure lid blank (10) into a closure lid (4). Method for manufacturing a closure device according to one of claims 1 to 13 and in particular according to claim 14, characterized by the following steps: - Inserting the closure cover (4) into the recess (3); - Welding, in particular laser welding, of the closure cover (4) to the lid (3).

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