Method for producing a cell housing for a battery cell of a motor vehicle traction battery, and corresponding cell housing

Abstract

The invention relates to a method for producing a cell housing (2) for a battery cell (1) of a motor vehicle traction battery, wherein the cell housing (2) has a peripherally enclosed interior space (3) and openings (8) on opposite sides which can be closed by means of housing covers (9). The cell housing (2) is produced by means of roll forming, wherein, prior to the roll forming, a wall thickness of the cell housing (2) is locally reduced and / or at least one recess (13, 22, 24, 26) is produced in a housing wall (4, 5, 6, 7) of the cell housing (2). The invention further relates to a cell housing (2) for a battery cell (1) of a motor vehicle traction battery.

Description

[0001] DESCRIPTION

[0002] Method for producing a cell housing for a battery cell of a traction battery of a motor vehicle and corresponding cell housing

[0003] The invention relates to a method for producing a cell housing for a battery cell of a traction battery of a motor vehicle, wherein the cell housing has a circumferentially enclosed interior space and openings on opposite sides that can be closed by means of housing covers. The invention further relates to a cell housing.

[0004] From the prior art, for example, the document US 2019 / 0 393 456 A1 is known. This describes a battery module housing with a rectangular tubular structure, which comprises a first side plate and a second side plate, wherein the first side plate and the second side plate have target portions at their upper and lower ends, respectively, and spacers that protrude vertically from the target portions. Furthermore, the battery module housing has an upper plate and a lower plate, which are arranged at upper and lower portions of the first and the second side plates, respectively, wherein the upper and the lower plates each have wing portions that are supported by the spacers of the first and the second side plates.The wing sections of the upper and lower plates are joined to the target sections by electromagnetic pulse welding such that the outer sections of the wing sections contact the target sections and the inner sections of the wing sections are separated from the target sections by a gap.

[0005] Furthermore, the document DE 10 2020 105 607 B3 discloses a battery module of a traction battery of a motor vehicle, with a module housing through which a cooling medium flows, with a plurality of battery cells arranged in the module housing and which can be cooled via the cooling medium, wherein the module housing has a base body designed as an extruded profile and open at the end faces, and wherein the module housing further has end plates which are inserted into the base body designed as an extruded profile and are welded to the extruded profile in a fluid-tight manner all around.

[0006] The object of the invention is to propose a method for producing a cell housing for a battery cell, which has advantages over known methods, in particular enables rapid and cost-effective production of the cell housing with a short cycle time and low and uniform wall thicknesses.

[0007] This is achieved according to the invention with a method for producing a cell housing for a battery cell having the features of claim 1. It is provided that the cell housing is produced by roll forming, wherein prior to roll forming a wall thickness of the cell housing is locally reduced and / or at least one recess is produced in a housing wall of the cell housing.

[0008] Advantageous embodiments with useful further developments of the invention are specified in the dependent claims. It should be noted that the exemplary embodiments explained in the description are not limiting; rather, any variations of the features disclosed in the description, the claims, and the figures are feasible.

[0009] The cell housing is preferably a component of the battery cell, but can of course also be separate from it, in particular prior to assembly of the battery cell. The battery cell itself is preferably part of a traction battery for a motor vehicle. The battery cell is designed in particular as a lithium-ion battery cell or as a dry battery cell. The traction battery is, for example, a component of the motor vehicle or is separate from it. The traction battery serves to temporarily store electrical energy for a drive device of the motor vehicle. The drive device is provided and designed to drive the motor vehicle, i.e. ultimately to provide a drive torque directed towards driving the motor vehicle. The drive device is electrically connected to the traction battery and is supplied with electrical energy by it, at least temporarily.Conversely, it can be provided that electrical energy generated by the drive device is stored in the traction battery.

[0010] The traction battery comprises at least one battery cell, i.e., precisely one or more battery cells, which are installed in a battery housing of the traction battery. Preferably, a plurality of such battery cells are arranged next to one another in the battery housing, namely in such a way that they abut one another in at least one direction, thereby supporting one another. Preferably, in addition to the at least one battery cell, an elastic element is arranged in the battery housing, which at least temporarily generates a pressing force that compresses the battery cells in the aforementioned direction. The elastic element serves, in particular, to compensate for dimensional changes of the at least one battery cell. For example, the dimensions of the battery cell change depending on an ambient condition, such as an ambient temperature, an ambient pressure, or the like.Operating conditions of the battery cell and / or the age of the battery cell can also result in a change in dimensions.

[0011] The battery cell is preferably in the form of a prismatic battery cell. A prismatic battery cell is understood to be a battery cell that has a specific external shape, namely essentially a cuboid. This means that the cell housing is cuboid-shaped or at least has a cuboid-shaped basic shape. Of course, however, it can be provided that at least one attachment is arranged on the cell housing or extends from the cell housing, so that the battery cell as a whole can deviate somewhat from the cuboid shape. For example, an opening and / or a recess is formed in the cell housing. Edges and / or corners of the cell housing can also be rounded.

[0012] The cell housing has one or more housing walls which completely and continuously enclose the interior in at least one direction or in an imaginary sectional plane. If the battery cell is round, it has, for example, only a single housing wall. In the case of a prismatic shape of the battery cell, there are preferably four housing walls, two of which are arranged parallel to one another or at least approximately parallel to one another. Viewed in cross-section with respect to a longitudinal central axis of the cell housing, the housing walls preferably have different extensions, so that two first housing walls are spaced closer together than two second housing walls. Each of the two first housing walls is connected to one of the second housing walls on opposite sides or merges into this.

[0013] The housing wall or the housing walls of the cell housing preferably have wall thicknesses of less than 2 mm, less than 1.75 mm or at most 1.5 mm. Particularly preferably, at least one of the housing walls is designed with a wall thickness of at most 1.0 mm, at most 0.8 mm or at most 0.6 mm. More preferably, the wall thickness is even smaller and amounts to at most 0.4 mm, at most 0.3 mm or at most 0.25 mm. Particularly preferably, the wall thickness of one of the housing walls is greater than a specific value, in particular 1 mm, and the wall thickness of another of the housing walls corresponds at most to the specific value, in particular it amounts to at most 1 mm. It can be provided that the wall thicknesses of opposite housing walls are identical. However, different wall thicknesses of opposite housing walls can also be implemented.

[0014] The cell housing has openings on opposite sides through which the interior opens into the exterior of the cell housing. The openings can be closed by housing covers; a first of the openings is thus closed by a first housing cover and a second of the openings is closed by a second housing cover, namely during assembly of the battery cell. The housing covers preferably close the openings completely, in particular in a fluid-tight manner. In particular, the housing covers are connected to the cell housing, preferably by a material bond, particularly preferably by welding.

[0015] Preferably, the housing covers have connection terminals for the battery cell, via which electrical contact can be made with the battery cell. The connection terminals are assigned to different potentials of the battery cell or different poles of the battery cell. Thus, preferably, one of the connection terminals represents a positive pole and another of the connection terminals represents a negative pole of the battery cell. The connection terminals are arranged on the outside of the battery cell so that they can be electrically contacted or are accessible for electrical contact from the outside environment. In the case of the prismatic battery cell, the connection terminals are preferably arranged on opposite sides of the battery cell, namely a first of the connection terminals on the first housing cover and a second of the connection terminals on the second housing cover.However, it can also be provided that both connection terminals are located on the same housing cover. The connection terminals are electrically connected to electrodes arranged in the cell housing. In addition to the electrodes, the cell housing contains an electrolyte, which is filled into the battery cell during its production. This occurs, in particular, through a filling opening. This can be made in one of the covers or in the cell housing.

[0016] In order to keep the weight of the battery cell as low as possible and to enable good heat conduction, the cell housing is made of light metal, in particular aluminum or an aluminum alloy. Particular preference is given to using a wrought aluminum alloy, which in particular belongs to the 3000 series of aluminum-manganese alloys or the 5000 series of aluminum-magnesium alloys. The aluminum alloy is particularly preferably naturally hard. For example, the alloys EN AW-1098, EN AW-1200, EN AW-3003, EN AW-3103, EN AW-5310 and EN AW-5754 are used as aluminum alloys. Particular preference is given to the alloy EN AW-3003, which is characterized by particularly good material properties. The aluminum alloy is therefore an aluminum-manganese-copper alloy (AlMnCu), in particular an aluminum-manganese-copper wrought alloy.However, steel, especially clad steel, preferably nickel-plated steel, can also be used. Due to the higher strength, thinner wall thicknesses are possible. The cladding achieves good media resistance. Roll forming of such a cladding is easily possible.

[0017] In order to manufacture the cell housing in a particularly economical manner, it should be carried out by roll forming. Roll forming is carried out in particular as cold roll forming and thus performs cold forming. It can also be referred to as roll forming. During roll forming, a semi-finished product is formed into the cell housing. The semi-finished product is understood to be the starting material of a manufacturing process in which it is formed into the desired shape for the cell housing by roll forming. The semi-finished product is manufactured from a semi-finished product that is provided for the process. The applicant's aim was to achieve shorter cycle times in the production of the cell housing than those achievable with other forming processes, for example deep drawing.However, it has been determined that manufacturing the cell casing using common bulk forming processes, such as extrusion, is not economically feasible. The reason for this is that, to achieve sufficient cost-effectiveness, extrusion must be performed using a large extrusion length. Due to the thin wall thickness of the cell casing walls, however, this process results in deformation of the cell casing, requiring either a shorter extrusion length or extensive post-processing of the cell casing.

[0018] For this reason, the cell housing is to be manufactured by roll forming. Roll forming is generally classified as bending according to DIN 8580, or more precisely as roll bending according to DIN 8586. The semi-finished product used is in particular a sheet metal, preferably a metal sheet. The cell housing is accordingly in the form of a formed sheet metal part or bent sheet metal part, or more precisely as a roll-formed part. To the applicant's surprise, it has been found that the cell housing can be manufactured by roll forming, even with short cycle times. In particular, tolerances for the wall thickness of the cell housing are reliably maintained. During roll forming, the semi-finished product is formed in such a way that two areas of the semi-finished product are arranged side by side or overlapping.These two areas are connected to each other, in particular in a material-locking and / or form-fitting manner, so that the cell housing has a closed cross-section.

[0019] In a first variant of the method for producing the cell housing, the wall thickness of the cell housing is to be reduced locally before roll forming, i.e. only in a limited area and not for the entire cell housing. The cell housing is characterized in this respect by different wall thicknesses that are produced before roll forming. Such a procedure has the advantage that during the production of the cell housing a structure is formed which either offers advantages directly during production or is subsequently required on the cell housing. For example, it is provided to reduce the wall thickness of the cell housing only locally such that a valve membrane for a burst valve is present on the cell housing. It can also be provided to reduce the wall thickness in a bending area of ​​the cell housing in order to improve bending of the semi-finished product in the bending area during roll forming.

[0020] The wall thickness is reduced in particular by forming, for example bulk forming, which is carried out before roll forming. The wall thickness is preferably reduced on the same production line that is also used for bending or roll forming the semi-finished product to manufacture the cell housing. For example, the reduction is carried out by means of at least a first processing stage of the production line and the bending is carried out by means of a second processing stage of the production line. The sequence of the processing stages is arbitrary. There can therefore first be at least a second processing stage, followed by a first processing stage and then again a second processing stage. In principle, however, the wall thickness is reduced first and only then is the bending carried out.

[0021] In a second variant of the method for producing the cell housing, at least one recess is produced in the housing wall of the cell housing prior to roll forming. The housing wall of the cell housing is understood to be a region of the cell housing which, in the case of a round battery cell, is curved or, in the case of a prismatic battery cell, is preferably flat at least in some regions, particularly preferably continuously. Provision can be made for the recess to be designed with a closed edge, i.e., with a continuous and uninterrupted edge that completely encompasses the recess. In principle, the recess already exists in the housing wall prior to roll forming. For example, the cell housing is formed in the region of the recess during roll forming. For example, the valve membrane mentioned above is located in such a recess.In this case, the recess is preferably formed at the same time as the valve membrane. Of course, it is also possible to create the recess in the cell housing after roll forming.

[0022] The process can be used either in the first variant or in the second variant, or both variants can be used together. The latter is particularly the case if the recess is created by locally reducing the wall thickness of the cell housing. In either case, the cell housing can be manufactured with a high level of dimensional accuracy and short cycle times, i.e. in a short time with high unit quantities, and at particularly low production costs. In addition, a very homogeneous material structure is achieved, especially away from an area in which the material-locking and / or form-fitting connection takes place, as well as high dimensional accuracy with regard to the wall thickness. The cell housing is also manufactured with a visually smooth and uniform surface.

[0023] Preferably, a semi-finished product is provided, in particular a sheet metal part. The semi-finished product is then converted into a semi-finished product by reducing the wall thickness and / or creating the recess. The semi-finished product is then rolled into the final shape of the cell housing. Wherever processing steps on the cell housing are discussed within the scope of this description, this includes both the semi-finished product and the semi-finished product. The terms semi-finished product and semi-finished product are used solely to refer to processing steps that take place prior to roll forming. The production of the cell housing therefore includes reducing the wall thickness and / or creating the recess as well as roll forming. The semi-finished product represents the starting material used for this process, while the semi-finished product is understood to be a partially manufactured cell housing.

[0024] A further development of the invention provides that the wall thickness is reduced by profile rolling, in particular strip profile rolling, or by flexible rolling. During the reduction of the wall thickness, the cell housing is preferably displaced in the same direction of movement as during roll forming. The feed direction during the production steps of the cell housing therefore does not change. Profile rolling serves in particular to reduce the wall thickness in the direction of movement of the cell housing during profile rolling, i.e. to reduce the wall thickness in an area that has its largest dimensions in the direction of movement. Preferably, the reduction of the wall thickness takes place continuously in the direction of movement. A recess or depression created in this process is therefore produced across the entire semi-finished product and is therefore present as an endless recess.

[0025] By means of flexible rolling, however, the wall thickness is preferably reduced in an area that has its greatest dimensions in a direction that is angled to the direction of movement, in particular at right angles to it. Flexible rolling causes, in particular, a local elongation of the semi-finished product, which is preferably taken into account when manufacturing the cell housing. Flexible rolling is a cold rolling process in which different wall thicknesses can be produced using an adjustable roll gap. For example, the wall thickness of the cell housing is reduced locally by at least 30%, at least 40%, or at least 50%, based on a wall thickness of the semi-finished product. This allows targeted structures of the cell housing to be manufactured. For example, the reduction in wall thickness is used to design at least one stiffening profile, for example a stiffening bead, on the cell housing.Flexible rolling is also called TRB rolling (TRB: Tailored Rolled Banks).

[0026] A further development of the invention provides for the recess to be produced by punching or perforating. This is particularly the case if the recess is a through-hole. Punching is a simple and cost-effective method.

[0027] A further development of the invention provides that after reducing the wall thickness and / or after creating the recess, and before roll forming, the cell housing is machined. Reducing the wall thickness or creating the recess can result in a dimensional change in the semi-finished product, so that it has different external dimensions than the semi-finished product. For example, widening occurs, i.e. an increase in dimensions transverse to the feed direction. Machining preferably serves to reduce the width of the semi-finished product and thus adjust it to a desired width. This achieves particularly good dimensional accuracy. A further development of the invention provides that the cell housing is closed with a material fit and / or form fit after roll forming. After roll forming, it is necessary to finally close the cell housing.This is preferably done by a material-to-material bond, for example, by welding or soldering, or by a form-fitting bond, for example, by flanging. Sealing is achieved, for example, by joining adjacent areas of the cell casing together, namely by a material-to-material bond and / or a form-fitting bond. Joining, for example, creates a seam on the cell casing, which seals it. In the case of welding, the seam can also be referred to as a weld seam. In either case, the objectives mentioned above are achieved.

[0028] A further development of the invention provides that the cell housing is cut to length after roll forming, in particular after closing. Cutting the cell housing to length preferably takes place only after roll forming. Until cutting to length, the cell housing is integrally connected to other areas of the semi-finished product. In particular, before cutting to length, the cell housing has a length that significantly exceeds its final length, for example, at least 50%, at least 75%, or at least 100% longer. Cutting to length is carried out, for example, by machining, in particular by sawing.

[0029] A further development of the invention provides that the wall thickness of the cell housing is reduced in a bending region of the cell housing and subsequently the cell housing is bent along the bending region during roll forming, and / or that the wall thickness of the cell housing is reduced in connecting regions of the cell housing and subsequently the connecting regions are connected to one another in a material-locking and / or form-fitting manner. For example, the reduction in wall thickness takes place in the bending region. The wall thickness in the bending region is selected such that particularly favorable properties of the cell housing are achieved during the subsequent bending or bending process in the bending region or along the bending region. For example, a recess is produced in the bending region in order to achieve a particularly tight bending radius during bending.Particularly preferably, the bending region has a specific longitudinal extension, preferably in the direction of movement, and the cell housing is subsequently bent along the bending region, preferably in the aforementioned direction across the entire bending region. In the case of a prismatic battery cell, for example, several parallel, spaced-apart bending regions are produced, in each of which the wall thickness of the cell housing is reduced. The cell housing is subsequently bent along these bending regions to achieve the prismatic shape of the cell housing.

[0030] Additionally or alternatively, the wall thickness of the cell housing is reduced in connecting regions. These connecting regions are subsequently connected to one another, namely by a material fit and / or form fit. The connecting regions are located in particular at an edge of the semi-finished product, thus forming, for example, a free edge of the semi-finished product. The connecting regions are preferably arranged so as to overlap one another and are subsequently fastened or connected to one another. For example, the wall thickness is selected such that the wall thickness of the cell housing in the connecting regions corresponds overall to the wall thickness of the cell housing away from the connecting regions, in particular directly adjacent to the connecting regions. As a result, the wall thickness of the cell housing remains constant or at least substantially constant even after the connecting regions have been connected to one another.However, it is particularly preferred to use both of the described variants, so that both the bending area and the connecting areas are created by reducing the wall thickness of the cell housing. This allows for particularly efficient production of the cell housing.

[0031] A further development of the invention provides that the material-to-material connection is carried out by welding or soldering and / or the form-fitting connection is carried out by flanging. As already mentioned, the connection of the connecting regions is carried out material-to-material connection, form-fitting connection, or by a combination of material-to-material and form-fitting connection. Form-fitting connection in the form of flanging comprises reshaping the connecting regions such that they engage with one another. Flanging thus results in a multi-layer design of the cell housing, in particular a design with at least four layers. In any case, a reliable holding of the connecting regions to one another is ensured. Preferably, the wall thickness in the connecting regions is reduced. However, this is not necessary. It can also be provided that the wall thickness of the connecting regions corresponds to the wall thickness of an adjacent region of the cell housing.For example, in this case the connecting areas are arranged butt-jointed and connected to each other, namely in the manner described.

[0032] A further development of the invention provides that, during the flanging process, a connecting means is arranged between the connecting areas and subsequently melted at least partially by heat treatment. The connecting means serves, for example, to create the integral connection. It can be a solder used for soldering. Alternatively, the connecting means is a sealant, for example a polymer, in particular a thermoplastic, which is melted at least partially by heat treatment so that it fits particularly tightly against the connecting areas. In either case, a particularly reliable connection between the connecting areas is created.

[0033] A further development of the invention provides that the recess is produced as a depression or as a passage opening. The term “depression” is understood to mean a recess which only partially extends through the cell housing or the housing wall. In this respect, the depression has a base which delimits it in a direction facing away from an opening of the depression. In contrast, the passage opening extends continuously through the cell housing or the housing wall. The passage opening is thus characterized by two spaced-apart openings which are arranged on opposite sides of the housing wall. By producing the depression or the passage opening, desired features of the cell housing can be designed at an early stage, for example during roll forming.

[0034] A further development of the invention provides that the reduction in wall thickness takes place by forming a first depression that extends through a first surface of the cell housing on a first side and by forming a second depression that extends through a second surface of the cell housing on a second side opposite the first side. Of course, the reduction in wall thickness can only be carried out on one of the sides of the cell housing or of the semi-finished product, so that either the first depression or the second depression is produced. However, it is particularly preferred to form depressions on opposite sides of the cell housing or of the semi-finished product in order to locally reduce the wall thickness of the cell housing there. The first depression and the second depression can overlap with one another.Preferably, however, they are spaced apart from each other in cross-section, so that they are not directly opposite each other.

[0035] The first recess and the second recess preferably have different cross-sectional shapes. Preferably, the first recess is wider than the second recess. It can be provided that the first recess is produced to set a defined wall thickness of the housing wall, whereas the second recess serves to produce the bending region. Particularly preferably, a plurality of first recesses are formed on the first side and / or a plurality of second recesses are formed on the second side. Preferably, the cross-sectional shapes of the first recesses are identical or at least similar to one another. This also applies additionally or alternatively to the cross-sectional shapes of the second recesses. With such a procedure, a particularly flexible shaping of the cell housing is implemented.

[0036] A further development of the invention provides that the cell housing is provided with a coating, at least in some regions, in particular prior to roll forming. The coating is, for example, in the form of a film coating, which is particularly preferably applied to the inside and / or outside of the cell housing. The coating serves, in particular, to provide electrical insulation. It is preferred to apply the coating prior to roll forming. However, this can also be done during roll forming or only after roll forming. The coating achieves particularly advantageous properties of the cell housing.

[0037] A further development of the invention provides that the recess is produced by forming, separating, or ablation. Forming is used in particular if the recess is in the form of a depression. Cutting or removing, however, is preferably used when producing the recess as a passage opening. Forming is in particular pressing, for example extrusion, or the aforementioned strip profile rolling or flexible rolling. During the forming process, bulk forming of the semi-finished product or the cell housing is carried out. Separating is particularly preferably punching, whereas removal is preferably carried out by laser ablation. The described procedure enables a flexible design of the cell housing.

[0038] A further development of the invention provides that the cell housing is moved in a direction of movement during roll forming and the recess is limited in the direction of movement. The direction of movement corresponds in particular to a longitudinal direction of the semi-finished product or semi-finished product, i.e. a direction in which the semi-finished product or semi-finished product has its largest dimensions. In this respect, the direction of movement can also be referred to as the longitudinal direction of the semi-finished product or semi-finished product. A transverse direction and a vertical direction are each perpendicular to the longitudinal direction and are also arranged perpendicular to one another. The longitudinal direction, the transverse direction and the vertical direction thus form a Cartesian coordinate system with one another. The material thickness of the semi-finished product or semi-finished product is in the vertical direction, and its width is in the transverse direction.The recess is designed or manufactured in such a way that it has limited dimensions in the direction of movement or in the longitudinal direction. In particular, the recess is delimited in the longitudinal direction by two spaced-apart edges, at which the material thickness of the semi-finished product or cell housing changes, in particular abruptly. For example, the recess extends completely through the semi-finished product in the transverse direction. However, only a partial extension of the semi-finished product in the transverse direction can also be implemented. Such a design of the recess enables flexible production of the cell housing.

[0039] A further development of the invention provides that the recess is angled relative to the bending region and / or the connecting regions. This particularly means that a longitudinal center axis of the recess is at an angle greater than 0° and less than 180° relative to a longitudinal center axis of the bending region and / or a longitudinal center axis of the connecting regions. The angle is preferably 45° to 135°, 60° to 120°, 80° to 100°, or approximately or exactly 90°. In the latter case, the recess is perpendicular to the bending region or the connecting regions.

[0040] For example, the recess therefore has its largest dimensions in the transverse direction. In other words, the transverse dimensions of the recess are larger than the longitudinal dimensions and larger than its vertical dimensions. However, it can also be provided that the recess runs parallel to the bending area or the connecting areas and is spaced apart. The specific orientation of the recess depends on its intended use. In any case, the described method allows for a high degree of flexibility with regard to the design of the cell housing.

[0041] A further development of the invention provides that the recess is produced in such a way that, after the cell housing has been produced, it forms a continuous step, in particular encompasses one of the openings at least in part, preferably completely. The recess can in principle be produced in any way, for example, it is formed before roll forming. The recess should form the step, in particular a step that is continuous in the circumferential direction with respect to a longitudinal center axis of the cell housing. This means that the step completely encompasses the longitudinal center axis in the circumferential direction. Preferably, the recess is arranged in the region of one of the openings, in particular it is directly adjacent to the opening and / or encompasses the opening at least in part, preferably completely. Preferably, the edge lies continuously in an imaginary plane which is, for example, perpendicular to the longitudinal center axis of the cell housing.The recess forms one edge of the opening. The wall thickness of the cell housing changes at the step. Thus, within the opening, the cell housing has a cross-sectional area up to the step that is larger than its cross-sectional area on the side of the step facing away from the opening. Conversely, the wall thickness of the cell housing, starting from the opening up to the step, is smaller than on the side of the step facing away from the opening. The step preferably forms an end stop for the housing cover associated with the opening, allowing the housing cover to be installed particularly easily in the opening.

[0042] A further development of the invention provides that the roll forming is carried out in such a way that the cell housing is double-walled at least in some regions, and / or that the cell housing is assembled from a plurality of sub-housings produced separately from one another by roll forming, in particular in such a way that the sub-housings overlap one another in some regions to give the cell housing a double-walled design. The cell housing is deformed during roll forming in such a way that a plurality of regions of the cell housing lie against one another and the cell housing is double-walled in some regions. Accordingly, two housing walls of the cell housing are directly adjacent to one another, in particular they lie directly against one another with their surfaces. The housing walls are preferably designed as a single piece and from the same material, or they are part of the cell housing designed as a single piece and from the same material.

[0043] However, the cell housing can also be composed of several sub-housings. For example, this is how the double-walled design of the cell housing is realized. The sub-housings are manufactured separately from one another by roll forming and subsequently assembled together to produce the cell housing. The sub-housings are preferably fastened to one another in a material-to-material and / or form-fitting manner, for example by welding, soldering and / or flanging. The sub-housings can be flush with one another, i.e. arranged butt-to-end. However, the cell housing is preferably assembled from the sub-housings in such a way that the cell housing is designed to be double-walled at least in some regions, namely by the sub-housings overlapping in some regions so that the housing walls present on them lie directly against one another. This ensures a high level of stability of the cell housing.For example, it is provided that the cell housing is manufactured from a semi-finished product with a base wall thickness, and that the wall thicknesses of the cell housing are selected according to an integer multiple of the base wall thickness. Thus, one of the housing walls is designed with a wall thickness corresponding to the base wall thickness, while another of the housing walls has a wall thickness that corresponds to a multiple of the base wall thickness. It can also be provided that one of the sub-housings is designed as the base housing with a continuous first wall thickness, and then another of the sub-housings is used to design the cell housing with a greater wall thickness.

[0044] In any case, it can be provided that the above-mentioned recess is made in only one of the adjacent housing walls, in particular on an outer one of the housing walls. However, it can also be provided that a recess is made in each of the housing walls, wherein at least in the outer housing wall the recess is present as a passage opening. The recesses are arranged to overlap with one another. The roll forming of the cell housing and / or the assembly of the partial housings is therefore carried out in such a way that the housing walls are arranged relative to one another such that the recesses overlap with one another, in particular centered relative to one another. It can be provided that the recesses have the same dimensions; in this case, they or their edges are preferably aligned with one another.Preferably, however, the dimensions of the recesses are different from one another, in particular the dimensions of the recess of the outer housing wall are larger or smaller than the dimensions of the recess of the inner housing wall.

[0045] Preferably, a first of the housing walls, which has a first wall thickness, is provided with the valve membrane. A second of the housing walls is then arranged in a flat, adjacent manner to this first housing wall, with a recess being created in this second housing wall that overlaps the valve membrane. The second housing wall can have the same wall thickness as the first housing wall or, alternatively, a greater wall thickness, in particular a wall thickness that corresponds to an integer multiple of the wall thickness of the first housing wall.

[0046] A further development of the invention provides that by locally reducing the wall thickness and / or creating the recess, a valve membrane of a bursting valve is formed, in which a bursting line is designed for setting a specific bursting pressure of the bursting valve. Depending on the state of the battery cell and / or ambient conditions, a specific internal pressure exists in the cell housing. For example, due to a defect in the battery cell, the internal pressure can increase significantly. To prevent an uncontrolled bursting of the cell housing, the cell housing has the bursting valve, which is provided and designed for the controlled opening of the cell housing, namely as soon as the internal pressure of the cell housing exceeds a specific bursting pressure of the bursting valve.

[0047] In a first state of the burst valve, which exists as long as the internal pressure in the cell housing is lower than the burst pressure, the burst valve closes the cell housing. In a second state, which exists as soon as the internal pressure has reached or exceeded the burst pressure, the burst valve is open, so that a flow connection is established between an interior of the battery cell enclosed by the cell housing and an external environment of the cell housing, namely via the burst valve. In the second state, the burst valve releases the interior fluidically towards the external environment, namely permanently from the moment the internal pressure reaches or exceeds the burst pressure. The opening of the burst valve is therefore irreversible.

[0048] In order to be able to produce the cell housing cost-effectively in large series, the bursting valve is to be manufactured directly on the cell housing, namely on a housing wall of the cell housing. In this case, there is no need to produce a valve receptacle in the housing wall. Instead, the valve membrane is formed directly on the housing wall by machining it. The bursting line is formed in the valve membrane created in this way. The bursting line is in the form of a score line. A score line is a depression that only partially penetrates the valve membrane and serves as a predetermined breaking point or breaking line or as a predetermined tearing point or tearing line. The valve membrane of the bursting valve therefore tears preferentially and / or first at or along the bursting line when the bursting pressure is reached or exceeded due to the internal pressure.

[0049] In other words, the burst line is a local depression that exists in the valve membrane or in the valve area. In the area of ​​the burst line, the wall thickness of the valve membrane is thinner than away from the burst line. The burst line runs along a center line, which can be, for example, continuously straight, continuously curved, or partially straight and partially curved. The burst line preferably has its greatest extent in the direction in which the valve membrane also has its greatest extent. The burst line is designed such that the valve membrane is set to the desired burst pressure. Using this procedure, subsequent arrangement of the valve membrane on the cell housing can be dispensed with.

[0050] A further development of the invention provides that the recess is produced with a continuous edge which has a smaller wall thickness than the cell housing immediately adjacent to the recess. The recess is preferably in the form of a through-opening, i.e. it extends completely through the housing wall. The recess is delimited by the continuous edge. The edge is designed with a reduced wall thickness so that it has a support surface which is set back from an inner or outer side of the cell housing, thus providing a valve receptacle for a valve diaphragm. After the cell housing has been roll-formed, the separately produced valve diaphragm is arranged, in particular fastened, on this support surface in such a way that it completely closes the recess. The fastening is carried out in particular by welding the valve diaphragm to the support surface. The bursting line is preferably already formed in the valve diaphragm.This ensures efficient production of the cell housing. With this approach, the valve receptacle is first manufactured on a wall of the cell housing, which is then sealed with the burst valve or a valve membrane of the burst valve. This approach also fundamentally enables the aforementioned advantages to be achieved.

[0051] The invention further relates to a cell housing for a battery cell of a traction battery of a motor vehicle, in particular manufactured by the method according to the explanations in the context of this description, wherein the cell housing has a circumferentially enclosed interior and openings on opposite sides that can be closed by housing covers. It is provided that the cell housing is manufactured by roll forming, wherein, prior to roll forming, a wall thickness of the cell housing is locally reduced and / or at least one recess is created in a housing wall of the cell housing.

[0052] The advantages of such a design of the cell housing or such a procedure have already been pointed out. Both the cell housing and the method for its production can be further developed in accordance with the statements in the context of this description, so that reference is made to these in this regard. The features and combinations of features described in the description, in particular the features and combinations of features described in the following description of the figures and / or shown in the figures, can be used not only in the respectively specified combination, but also in other combinations or on their own, without departing from the scope of the invention. Thus, embodiments are also to be regarded as encompassed by the invention that are not explicitly shown or explained in the description and / or the figures, but which arise from or can be derived from the explained embodiments.

[0053] The invention will be explained in more detail below with reference to the exemplary embodiments shown in the drawings, without limiting the invention. In the drawings:

[0054] Figure 1 is a schematic representation of components of a battery cell for a traction battery of a motor vehicle,

[0055] Figure 2 is a schematic representation of a portion of the cell casing during its manufacture,

[0056] Figure 3 shows a further schematic representation of the cell housing during its manufacture, as well as

[0057] Figure 4 is a schematic representation of a semi-finished product for producing the cell housing.

[0058] Figure 1 shows a schematic representation of components of a battery cell 1, such as is used for a traction battery of a motor vehicle. The battery cell 1 has a cell housing 2, which is essentially hollow cylindrical or hollow cuboid-shaped and accordingly has an interior space 3 that is enclosed in at least one direction by housing walls 4, 5, 6 and 7. The cell housing 2 is open on both sides, so that it has openings 8 there, only one of which is visible here. The housing walls 4, 5, 6 and 7 together form an edge for each of the openings 8. The openings 8 of the cell housing 2 can be closed by means of housing covers 9, which also form a component of the battery cell 1.

[0059] The housing walls 4 and 5 are arranged parallel to one another, as are the housing walls 6 and 7. The housing walls 4 and 5 can also be referred to as side walls of the cell housing 2, the housing wall 6 represents an upper side wall and the housing wall 7 represents a lower side wall. The housing walls 4 and 5 are spaced apart from one another by a smaller distance than the housing walls 6 and 7, for example the distance between the housing walls 6 and 7 is greater by a factor of at least 3, at least 4 or at least 5 than the distance between the housing walls 4 and 5. The housing walls 4 and 5 are therefore wider than the housing walls 6 and 7, which are correspondingly narrower. Connection terminals 10 for electrically contacting the battery cell 1 or a cell pack arranged in the cell housing 2 are arranged on the housing covers 9.

[0060] The cell housing 2 is manufactured by roll forming. A burst valve 11 is manufactured in a first embodiment on the housing wall 6. The burst valve 11 is manufactured during the production of the cell housing 2. To manufacture the burst valve 11, a valve membrane 12 of the burst valve 11 is first produced, namely by locally reducing a wall thickness of the housing wall 6, which preferably takes place before roll forming. In this process, the wall thickness of the housing wall 6 is reduced starting from an initial wall thickness, so that a recess 13 in the form of a depression is formed, which is delimited by a depression edge 14 and a depression bottom 15.

[0061] The local reduction of the wall thickness is achieved by forming, in particular bulk forming, which is carried out before roll forming, preferably using the same production line as the roll forming. Preferably, the local reduction of the wall thickness is carried out by strip profile rolling or flexible rolling. The recess 13 is closed at the edge, so that the recess edge 14 completely and continuously surrounds the recess 13. The recess base 15, on the other hand, delimits the recess 13 in the direction of the interior space 3 or—if the recess 13 is produced starting from the interior space 3 in the housing wall 6—to the outside.

[0062] The recess 13 is produced or the wall thickness is locally reduced in such a way that the recess 13 only partially extends through the housing wall 6, so that the recess base 15 completely and continuously closes the recess 13. A longitudinal center axis of the burst valve 11 or of the recess 13 is designated by the reference symbol xi. Further axes X2 and X3 are perpendicular to the longitudinal center axis xi, with the axes X2 and X3 also being perpendicular to one another. The axes xi, X2 and X3 thus span a Cartesian coordinate system. The two axes X2 and X3 preferably also lie in an imaginary plane which corresponds to a center plane of the housing wall 6 at least in the region of the burst valve 11, i.e. in a valve region 16, or is arranged parallel to this.The center plane preferably intersects the recess edge 14 continuously and uninterruptedly, thus forming a continuous and uninterrupted intersection line with the recess edge 14. In the direction of the axes X2 and X3, the burst valve 11 overlaps the housing wall 6 only partially, for example, in the direction of the axis X2 by a maximum of 20%, a maximum of 15%, or a maximum of 10%. In the direction of the axis X3, the burst valve 11 overlaps the housing wall 6 by a maximum of 70%, a maximum of 60%, or a maximum of 50%.

[0063] Preferably, after the local reduction of the wall thickness of the housing wall 6 to form the valve membrane 12, at least one bursting line 17 is formed in the valve membrane 12. This can take place before or after roll forming. In the illustrated embodiment, in addition to the bursting line 17, there is a further bursting line 18, wherein the bursting lines 17 and 18 are arranged at a distance from one another in some regions and run together in some regions. The bursting lines 17 and 18 are arranged at a continuous distance from the recess edge 14. For example, they are arranged centrally in the recess 13 and in the valve membrane 12, respectively, with respect to both the axis X2 and the axis X3. They extend in a first direction over at least 40%, at least 50%, or at least 60% and over at most 90%, at most 80%, or at most 70% of the extent of the recess 13 in this direction.In a second direction perpendicular to the first direction, the bursting lines 17 and 18 overlap the recess 13 by at least 40%, at least 50%, or at least 60%, and again by at most 90%, at most 80%, or at most 70%. The first direction preferably extends along the X2 axis, and the second direction extends along the X3 axis.

[0064] The burst lines 17 and 18 are preferably produced by embossing and can therefore also be referred to as stamped lines. It can be seen that both burst lines 17 and 18 are encompassed by a respective calibration area 19 and 20, respectively. In the calibration areas 19 and 20, the wall thickness of the housing wall 6 is reduced compared to the wall thickness of the valve membrane 12, but not as much as in the burst lines 17 and 18. The calibration areas 19 and 20 serve to set a precisely defined wall thickness of the housing wall 6 around the burst lines 17 and 18, in particular to reduce or even completely eliminate tolerances that occur during the local reduction of the wall thickness for producing the valve membrane 12.

[0065] The bending of the cell housing 2 during roll forming takes place along bending areas

[0066] 21. In the bending areas 21, which preferably form the edges of the cell housing 2 after its manufacture, the wall thickness of the cell housing 2 is reduced. The wall thickness is reduced before roll forming, in particular by rolling, preferably strip profile rolling or flexible rolling. Furthermore, on the cell housing 2, preferably on each of its housing walls 4, 5, 6, and 7, there is a recess 22, which is designed as a depression and only partially extends through the respective housing wall 4, 5, 6, and 7. The recesses 22 form a continuous step 23, at which the wall thickness of the cell housing 2 increases in the direction away from the respective opening 8. The step 23 forms a bearing shoulder for the respective housing cover 9.

[0067] Figure 2 shows a schematic representation of a region of the cell housing 2 during its manufacture. It can be seen that the local reduction in the wall thickness of the cell housing 2 takes place on opposite sides of the cell housing 2, in particular by strip profile rolling, so that a first recess 24 designed as a depression extends through a first surface 25 on a first side of the cell housing 2 and a second recess 26 designed as a depression extends through a second surface 27 on a second side of the cell housing 2. In the exemplary embodiment shown, there are several first recesses 24 and several second recesses 26. The first recesses 24 have the same cross-sectional shapes as one another, for example, they are each rectangular when viewed in cross section. The second recesses 26 also have the same cross-sectional shapes as one another, for example, they are triangular or trapezoidal when viewed in cross section.In any case, the second recesses 26 have smaller dimensions in the transverse direction than the first recesses 24. The second recesses 26 form the bending regions 21 already mentioned.

[0068] Figure 3 shows a further schematic representation of the cell housing 2 during its production. A tool 28 is also shown, which is preferably used within the production line. The tool 28 is in the form of a cam that rotates about a rotational axis 29. The cam can also be referred to as a cam roller. Due to its eccentric design, the tool 28 only temporarily acts on the cell housing 2; in particular, the recess 13 and thus the valve membrane 12 are produced using the tool 28. A resulting widening 30 of the cell housing 2 is removed, for example, by machining, preferably before roll forming. Figure 4 shows a schematic representation of a semi-finished product 31 for producing the cell housing 2.Roll forming is carried out on the basis of the semi-finished product 31, i.e., the semi-finished product 31 is formed into the cell housing 2 by roll forming. During this process, the semi-finished product 31 is displaced in a direction of movement indicated by arrow 32. Visible again are the recess 22 and the step 23 formed thereby, which are intended to encompass the openings 8 after the cell housing 2 has been produced. For this purpose, it is preferably provided to cut the semi-finished product 31 to length in the recess 22, preferably centrally. It is provided to produce the recess 22 in a semi-finished product prior to roll forming in order to thus form the semi-finished product 31. The described cell housing 2 for the battery cell 1 and the explained method for producing the cell housing 2 enable great flexibility. Furthermore, the cell housing 2 can be manufactured cost-effectively in large series.

[0069] The cell housing 2 is particularly advantageously manufactured using the following steps: rolling, in particular strip profile rolling; punching; rolling, in particular flexible rolling; roll forming; joining. One or more of the steps are preferably carried out in the specified order. It can therefore be provided that firstly a first of the recesses 13, 22, 24 and 26 is produced in one of the housing walls 4, 5, 6 and 7, namely by rolling, preferably by strip profile rolling. Subsequently, a second of the recesses 13, 22, 24 and 26 is produced, namely by punching. A third of the recesses 13, 22, 24 and 26 is again produced by rolling, in particular flexible rolling. Subsequently, the cell housing 2 is shaped by roll forming and then closed by joining, in particular by material bonding and / or form-fitting, for example by welding, soldering and / or flanging.

[0070] LIST OF REFERENCE SYMBOLS

[0071] 1 battery cell

[0072] 2 cell housings

[0073] 3 Interior

[0074] 4 Housing wall

[0075] 5 Housing wall

[0076] 6 Housing wall

[0077] 7 Housing wall

[0078] 8 Opening

[0079] 9 Housing cover

[0080] 10 connection terminal

[0081] 11 Burst valve

[0082] 12 valve membrane

[0083] 13 Recess

[0084] 14 recess edge

[0085] 15 recessed floor

[0086] 16 valve area

[0087] 17 Berstritz Line

[0088] 18 Berstritz Line

[0089] 19 Calibration range

[0090] 20 Calibration range

[0091] 21 Bending area

[0092] 22 Recess

[0093] 23 Level

[0094] 24 1. Recess

[0095] 25 1. Surface

[0096] 26 2nd recess

[0097] 27 2. Surface

[0098] 28 tools

[0099] 29 axis of rotation

[0100] 30 Widening

[0101] 31 semi-finished products

[0102] 32 Arrow

Claims

CLAIMS 1. Method for producing a cell housing (2) for a battery cell (1) of a traction battery of a motor vehicle, wherein the cell housing (2) has a circumferentially enclosed interior space (3) and openings (8) which can be closed on opposite sides by means of housing covers (9), characterized in that the cell housing (2) is produced by roll forming, wherein before roll forming a wall thickness of the cell housing (2) is locally reduced and / or at least one recess (13, 22, 24, 26) is produced in a housing wall (4, 5, 6, 7) of the cell housing (2).

2. Method according to claim 1, characterized in that the wall thickness of the cell housing (2) is reduced in a bending region (21) and subsequently the cell housing (2) is bent along the bending region (21) during roll forming, and / or that the wall thickness of the cell housing (2) is reduced in connecting regions of the cell housing (2) and subsequently the connecting regions are connected to one another in a materially bonded and / or form-fitting manner.

3. Method according to one of the preceding claims, characterized in that the material connection is carried out by welding or soldering and / or the form-fitting connection is carried out by flanging.

4. Method according to one of the preceding claims, characterized in that during the flanging a connecting means is arranged between the connecting regions and is subsequently melted at least in regions by a heat treatment.

5. Method according to one of the preceding claims, characterized in that the recess (13, 22, 24, 26) is produced as a depression or as a passage opening.

6. Method according to one of the preceding claims, characterized in that the reduction of the wall thickness takes place by forming a first depression penetrating a first surface (25) of the cell housing (2) on a first side and by forming a second depression penetrating a second surface (27) of the cell housing (2) on a second side opposite the first side.

7. Method according to one of the preceding claims, characterized in that the cell housing (2) is provided with a coating at least in some areas.

8. Method according to one of the preceding claims, characterized in that the recess is produced by forming, separating or removing.

9. Method according to one of the preceding claims, characterized in that the cell housing (2) is moved in a direction of movement during roll forming and the recess (13, 22, 24, 26) is limited in the direction of movement.

10. Method according to one of the preceding claims, characterized in that the recess (13, 22, 24, 26) is angled relative to the bending region (21) and / or the connecting regions.

11. Method according to one of the preceding claims, characterized in that the recess is produced in such a way that it forms a continuous step (23) after the cell housing (2) has been produced.

12. Method according to one of the preceding claims, characterized in that the roll forming is carried out in such a way that the cell housing (2) is double-walled at least in some regions, and / or that the cell housing (2) is assembled from a plurality of partial housings produced separately from one another by roll forming.

13. Method according to one of the preceding claims, characterized in that by locally reducing the wall thickness and / or producing the recess (13, 22, 24, 26), a valve membrane (12) of a bursting valve (11) is formed, in which a bursting line (17, 18) is designed for setting a specific bursting pressure of the bursting valve (11).

14. Method according to one of the preceding claims, characterized in that the recess (13, 22, 24, 26) is produced with a continuous edge which has a smaller wall thickness than the cell housing (2) immediately adjacent to the recess (13, 22, 24, 26).

15. Cell housing (2) for a battery cell (1) of a traction battery of a motor vehicle, in particular produced by means of the method according to one or more of the preceding claims, wherein the cell housing (2) has a circumferentially enclosed interior space (3) and openings (8) which can be closed on opposite sides by means of housing covers (9), characterized in that the cell housing (2) is produced by roll forming, wherein before roll forming a wall thickness of the cell housing (2) is locally reduced and / or at least one recess (13, 22, 24, 26) is made in a housing wall (4, 5, 6, 7) of the cell housing (2).

Images