Battery cell for a battery, method for manufacturing such a battery cell, and vehicle with a battery

Abstract

The present invention relates to a battery cell (1) for a battery, comprising a housing (5) defining a longitudinal center axis (4), which has a shell (7) circumferentially (6) around the longitudinal center axis (4) and ends (9) at opposite longitudinal ends of the housing (5). The shell (7) has an outer surface (11) extending away from the longitudinal center axis (4) and intended for coating with a potting compound (10), which has a surface structure (12) formed by circumferential grooves (13) introduced into the outer surface (11), in particular by rolling or hydroforming. The invention relates in particular to a method for manufacturing a battery cell (1) and further in particular to a vehicle with a battery comprising several battery cells (1) according to the invention.

Description

[0001] The invention relates to a battery cell for a battery according to the preamble of claim 1. The invention relates in particular to a method for producing such a battery cell and further in particular to a vehicle with a battery.

[0002] Conventional battery cells are encapsulated with a potting compound for mutual fixation, connection to a battery housing, and for liquid and gas sealing and / or electrical insulation. Due to the manufacturing process, the surfaces of the battery cells are smooth, which poses the risk that the connection created by the potting compound could fail due to mechanical stresses occurring during production and, in particular, during subsequent intended use.

[0003] A battery cell of the type mentioned above is known from document DE 10 2019 208 063 A1. It has a surface structured by means of an electron beam, to which a sealing or insulating element serving as a liquid and gas seal and / or electrical insulation is bonded. The structuring of battery cell surfaces using electron beam-based processes is uneconomical, particularly for the large quantities required, as these processes are comparatively difficult to manage on an industrial scale and are associated with relatively high time, personnel, and cost expenditure. Corrosion-protective coatings and coverings on the cell body surface are damaged by subsequent thermal pretreatment processes such as laser ablation. This means that corrosion protection on pretreated surfaces is sometimes no longer present and may have to be subsequently reapplied.

[0004] The object of the invention is therefore to provide an improved or at least a different embodiment of a battery cell. In particular, an advantageous method for producing such a battery cell and a vehicle with a battery are to be specified.

[0005] In the present invention, this object is achieved in particular by the subject matter of the independent claims. Advantageous embodiments are the subject matter of the dependent claims and the description.

[0006] A battery cell for a battery, in particular a traction battery of a vehicle, is proposed, comprising a housing defining a longitudinal center axis, a shell extending circumferentially around the longitudinal center axis, and bases at opposite longitudinal ends of the housing. Furthermore, said shell has an outer surface facing away from the longitudinal center axis, intended for wetting with a potting compound, pretreated in particular by a plasma, laser, or chemical process. Essential to the invention is that the outer surface has a surface structure formed by circumferential grooves introduced into the outer surface, in particular by rolling or hydroforming.

[0007] The circumferential grooves provided in the surface structure enlarge the outer surface in comparison to, for example, a smooth outer surface. This has the advantage that an improved bond between a potting compound applied to the outer surface and the housing can be achieved. This is because the enlarged outer surface provides a comparatively large contact area between the potting compound and the outer surface, so that shear and tensile forces in particular can be better transmitted, and an improved form fit between the potting compound and the outer surface is achieved. Furthermore, the enlarged outer surface improves heat transfer between the battery cell and the potting compound, so that more effective temperature control of the battery cell, in particular improved cooling, can be achieved.

[0008] The said potting compound is advantageously intended for securing the battery cell to an adjacent battery cell and / or to a battery housing of a battery. Furthermore, the potting compound can be used for liquid and gas sealing and / or electrical insulation of the battery cell. The potting compound can be a curable foam or a curable adhesive.

[0009] The invention understands the term "circumferential grooves" to mean a continuous, elongated depression in the outer surface. The circumferential grooves are particularly narrower than, for example, grooves. Furthermore, the circumferential grooves can each have a groove depth of <1 mm and preferably <1 µm, measured in the direction of a surface normal perpendicular to the outer surface, and / or a groove width of <1 mm and preferably <1 µm, measured transversely to the surface normal.

[0010] According to the understanding of the invention, the circumferential grooves extend in the circumferential direction or substantially in the circumferential direction across the outer surface. The term "in the circumferential direction" can be understood as the circumferential direction that rotates around the longitudinal center axis in a plane oriented orthogonally to the longitudinal center axis. Furthermore, the term "substantially in the circumferential direction" can be understood as any circumferential direction that rotates around the longitudinal center axis.

[0011] In an alternative embodiment, this also includes a spiral or helix that is created during rolling and rolling, and in a further alternative embodiment, surface structures that are not completely circumferential, such as those that are transferred to the surface of the component during sandblasting or by means of laser-structured hydroforming tools.

[0012] It can expediently be provided that the circumferential grooves form circumferential ring grooves that encircle the outer surface completely closed or at least partially in a ring shape. Alternatively, it can be provided that the circumferential grooves form circumferential spiral grooves that encircle the outer surface in a cylindrical spiral shape in the direction of the longitudinal center axis. This specifies two different embodiments for circumferential grooves. The circumferential ring grooves and / or the circumferential spiral grooves can preferably each be arranged coaxially to the longitudinal center axis. Furthermore, it can be provided that the circumferential ring grooves and / or the circumferential spiral grooves are arranged uniformly relative to one another in an axial direction along the longitudinal center axis, i.e. in particular in such a way that the circumferential ring grooves and / or the circumferential spiral grooves are equally spaced from one another in the axial direction.

[0013] Furthermore, it may be expedient for the circumferential grooves to be evenly distributed relative to one another in an axial direction parallel to the longitudinal center axis. The term "evenly distributed" can in particular mean that the geometric center lines of the circumferential grooves are equally spaced from one another in the axial direction.

[0014] It can be expediently provided that the circumferential grooves abut one another, in particular directly, in an axial direction parallel to the longitudinal center axis. In other words, the circumferential grooves merge seamlessly into one another in the axial direction of the longitudinal center axis. This allows a maximum enlargement of the outer surface to be achieved.

[0015] The invention has further established that the achievable enlargement of the outer surface of the casing can be influenced by the choice of the groove profile of the circumferential grooves. Accordingly, it can be expediently provided that the circumferential grooves have a groove profile that is wavy in an axial direction aligned parallel to the longitudinal center axis. The circumferential grooves expediently have successive rounded valleys and rounded peaks in the axial direction. Alternatively, it can be provided that the circumferential grooves have a groove profile that is jagged, in particular sawtooth-shaped or triangular-tooth-shaped, in an axial direction aligned parallel to the longitudinal center axis. The circumferential grooves expediently each have jagged, sawtooth-shaped or triangular-tooth-shaped groove cross-sections.Furthermore, a triangular-tooth-shaped groove profile can be provided, in which the circumferential grooves each have groove cross-sections shaped like an isosceles triangle. The outer surface can be enlarged using the specified, preferred groove profiles. Tests have shown that, for example, using the wave-shaped groove profile, a percentage increase in the outer surface of approximately 57% compared to a smooth outer surface can be achieved - purely as an example. Furthermore, using the triangular-tooth-shaped groove profile, a percentage increase in the outer surface of approximately 100% compared to a smooth outer surface can be achieved - again purely as an example.

[0016] It can also be expedient to provide for the circumferential grooves to be introduced into the outer surface by means of a rolling process or a hydroforming process. In comparison with electron beam-based processes, the circumferential grooves can thus be produced very cost-effectively and quickly. Furthermore, both the proposed rolling processes and the hydroforming processes are comparatively easy to master. The invention understands rolling processes to be expediently machining processes in which a fine chip is removed from the outer surface of the housing by means of a suitable rolling tool. This process can result in work hardening. This means that the outer surface of the housing can be hardened, at least in sections, by a rolling process. In particular, the hardness of a near-surface edge layer of the outer surface increases.The invention understands hydroforming processes as expediently non-machining forming processes in which the outer surface of the housing is permanently, i.e. plastically, formed by means of a suitable forming tool.

[0017] It is also conceivable for the housing to be manufactured at least in sections using a deep-drawing process. For example, a pot-shaped lower part of the housing, which in particular comprises the casing of the battery cell and a first base of the battery cell, can be manufactured from a sheet metal blank using a deep-drawing process. The pot-shaped lower part of the housing can then be closed by means of the second base of the battery cell, thus completing the housing. This enables cost-effective production of the proposed battery in large quantities.

[0018] It can expediently be provided that the circumferential grooves are arranged on at least one section of the outer surface, on several separate sections of the outer surface, or on the entire outer surface. Accordingly, the surface structure can be formed only locally on a section of the outer surface, in particular exclusively on a single section of the outer surface, on several separate sections of the outer surface, or on the entire outer surface. A remaining section of the outer surface, which together with the section of the outer surface or the several separate sections of the outer surface forms the entire outer surface, can have a surface structure that has no circumferential grooves, i.e., is free of circumferential grooves.

[0019] Furthermore, it is expedient if an inner surface of the casing facing the longitudinal center axis and opposite the outer surface is smooth, i.e. free of surface structures consisting of circumferential grooves.

[0020] Furthermore, it may be advantageous if the battery cell is a round battery cell that is rotationally symmetrical with respect to the longitudinal center axis. The battery cell bases are preferably circular and the casing circular-cylindrical.

[0021] This provides an advantageous, rotationally symmetrical round battery cell, wherein the outer surface of the casing can be particularly easily provided with a surface structure of circumferential grooves by means of a rolling process or a hydroforming process.

[0022] According to a further basic idea of ​​the invention, a method for producing a battery cell, in particular the battery cell according to the preceding description, is proposed, within the framework of which a housing defining a longitudinal center axis is provided, which has a shell running circumferentially around the longitudinal center axis and bases at opposite longitudinal ends of the housing. The shell has an outer surface facing away from the longitudinal center axis, intended for wetting with a potting compound, pretreated in particular by a plasma, laser, or chemical process, on which a surface structure is formed by circumferential grooves being introduced into the outer surface by means of a rolling process or a hydroforming process. As a result, a battery cell can be cost-effectively provided with the described, advantageous surface structure comprising circumferential grooves.The roller burnishing or hydroforming processes used are relatively simple to master and cost-effective, especially compared to laser machining of the outer surface, which is significantly more complex and cost-intensive. The battery cell can therefore be manufactured quickly and cost-effectively.

[0023] The invention understands a roller burnishing process to be expediently a machining process in which the unmachined outer surface is machined by means of a suitable roller burnishing tool, for example one or more roller burnishing rollers, with a force directed perpendicular to the outer surface (rolling force) so that a fine chip is removed from the outer surface of the housing. In this process, the yield point of the housing material is exceeded locally so that permanent plastic deformations, which the invention refers to as circumferential grooves, are created. In this process, the housing can be mounted on a clamping mandrel and its. During this process, work hardening can also occur. This means that the outer surface of the housing can be hardened at least in sections by a roller burnishing process. In particular, the hardness of a near-surface edge layer of the outer surface increases.The invention understands hydroforming processes as expediently non-machining forming processes in which the outer surface of the housing is permanently, i.e. plastically, formed by means of a suitable forming tool.

[0024] It can expediently be provided that the circumferential grooves are introduced into the outer surface on at least one section of the outer surface, on several separate sections of the outer surface or on the entire outer surface of the outer surface of the casing. As a result, the surface structure consisting of circumferential grooves is formed only locally on a section of the outer surface, in particular exclusively on a single section of the outer surface, on several separate sections of the outer surface or on the entire outer surface. In this case, a remaining section of the outer surface, which together with the section of the outer surface or the several separate sections of the outer surface forms the entire outer surface, can have a surface structure that has no circumferential grooves, i.e. is free of circumferential grooves.

[0025] It can be advantageous to perform a cleaning step prior to forming the surface structure of circumferential grooves, during which the outer surface of the casing is freed of contaminants using a plasma cleaning process, a laser cleaning process, or a chemical cleaning process. This allows any unwanted contaminants deposited on the outer surface of the casing to be removed, allowing the subsequent rolling or hydroforming process to be carried out without any loss of quality.

[0026] In particular, it can be provided that the battery cell is encapsulated with a potting compound, at least in the area of ​​the surface structure consisting of circumferential grooves. The potting compound is expediently intended for fixing the battery cell to an adjacent battery cell and / or to a battery housing of a battery. Furthermore, the potting compound can be used for liquid and gas sealing and / or electrical insulation of the battery cell.

[0027] According to a further basic idea of ​​the invention, a vehicle, in particular an electrically powered motor vehicle, is proposed which is equipped with a battery, in particular a traction battery, which has a plurality of battery cells according to the preceding description or a plurality of battery cells produced according to the previously described method. In this case, it can be provided that the battery has at least one assembly formed from a plurality of battery cells, which is framed by a cell frame of the battery and arranged in a battery housing of the battery. In this case, in order to fix the assembly of battery cells to the battery housing and to ensure liquid and gas sealing and / or electrical insulation of the battery cells, it can be provided that the assembly of battery cells or the battery cells are encapsulated in the said potting compound.

[0028] In summary, the invention expediently relates to a battery cell for a battery, comprising a housing defining a longitudinal center axis, a shell extending circumferentially around the longitudinal center axis, and bases at opposite longitudinal ends of the housing. The shell has an outer surface facing away from the longitudinal center axis, intended for wetting with a potting compound, and a surface structure formed by circumferential grooves introduced into the outer surface, in particular by rolling or hydroforming. The invention relates in particular to a method for producing a battery cell and, furthermore, in particular to a vehicle having a battery comprising a plurality of battery cells according to the invention.

[0029] Further important features and advantages of the invention emerge from the subclaims, from the drawings and from the associated description of the figures based on the drawings.

[0030] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0031] Preferred embodiments of the invention are illustrated in the drawings and are explained in more detail in the following description, wherein the same reference numerals refer to the same or similar or functionally identical components.

[0032] Showing schematically: Fig. 1 a preferred embodiment of a battery cell according to the invention in a perspective view, Fig. 2 the battery cell Fig. 1 in a sectional view looking towards a Fig. 1 arrow II and also an enlarged section of the outer surface of the battery cell, Fig. 3 in a sectional view circumferential grooves with a groove profile, Fig. 4 in a sectional view circumferential grooves with a further groove profile, Fig. 5 a greatly simplified rolling process for producing circumferential grooves.

[0033] The Fig. 1 and Fig. 2 show a battery cell 1 realized as a round battery cell 3, which can be used in particular in a traction battery of a vehicle (not shown here) for supplying a drive motor of the vehicle. The battery cell 1 has a rotationally symmetrical housing 5 defining a longitudinal center axis 4. The housing 5 in turn has a circumferential direction 6, which in Fig. 1 is indicated by an arrow, has a completely closed casing 7 surrounding the longitudinal center axis 4 and two opposing bottoms 9 at opposite longitudinal ends. The bottoms 9 of the battery cell 1 are, purely by way of example, circular in shape, and the casing 7 is circular-cylindrical.

[0034] It is intended that the battery cell 1 is provided with a connection to adjacent battery cells 1 and, if applicable, to a non-illustrated battery housing of the traction battery as well as for liquid and gas sealing and / or electrical insulation with a Fig. 2 indicated potting compound 10. For improved connection of the potting compound 10 to the housing 5, as particularly shown in Fig. 2, it is provided that the casing 7 of the housing 5 has an outer surface 11 which points radially away from the longitudinal center axis 4 and is designed to be wetted with casting compound 10 and which has a surface structure 12 which is formed by a plurality of circumferential grooves which, for the sake of clarity, are uniformly designated by the reference number 13.

[0035] The said circumferential grooves 13 in the present case are each elongated, connected depressions in the outer surface 11 which run in the circumferential direction 6 around the longitudinal center axis 4. The circumferential grooves 13 are evenly distributed to one another in an axial direction 14 aligned parallel to the longitudinal center axis 4 and lie directly against one another in the axial direction 14, i.e. they merge seamlessly into one another. Furthermore, the circumferential grooves 13 have a groove profile 15, 16. Due to the circumferential grooves 13, the outer surface 11 has a comparatively large area, so that the contact area between the potting compound 10 and the outer surface 11 is also relatively large. As a result, shear and tensile forces in particular can be transmitted better than before, resulting overall in an improved form fit between the potting compound 10 and the outer surface 11.As a result, the connection between the potting compound 10 and the outer surface 11 can also withstand mechanical stresses that occur during the manufacture of the traction battery and / or during subsequent intended operation of the traction battery.

[0036] The Fig. 2 and Fig. 3 show a preferred groove profile 15 of the circumferential grooves 13, by means of which an optimal enlargement of the outer surface 11 can be achieved. The proposed groove profile 15 is characterized by successive serrated, sawtooth-shaped, or triangular-tooth-shaped groove cross-sections of the circumferential grooves 13 in the axial direction 14. Furthermore, a triangular-tooth-shaped groove profile 15 can be provided, in which the circumferential grooves 13 each have groove cross-sections that are designed in the shape of an isosceles triangle. Fig. Figure 4 shows another preferred, wave-shaped groove profile 16. It is characterized by successive, rounded valleys and rounded peaks in the axial direction 14. Using the illustrated, preferred groove profiles 15, 16, the outer surface 11 can be significantly enlarged, resulting in an optimal bond between the potting compound 10 and the outer surface 11.

[0037] Finally, the Fig.5 shows a highly simplified method 17 for producing a battery cell 1. Within the scope of the method 17 shown, a housing 5 is first provided which defines a longitudinal center axis 4 and is rotationally symmetrical with respect to the longitudinal center axis 4, said housing 5 having a shell 7 which extends in a circumferential direction 6 around the longitudinal center axis 4 and has bases 9 at opposite longitudinal ends of the housing 5. The shell 7 has an outer surface 11 which points radially away from the longitudinal center axis 4 and is intended for wetting with a potting compound 10. A surface structure 12 is formed on the outer surface 11 by circumferential grooves 13 being introduced into the outer surface 11 by means of a rolling process.

[0038] The roller burnishing process described is relatively simple to master from a technical perspective. For example, during the roller burnishing process, an unmachined, e.g., smooth outer surface (not shown) of the housing 5 is machined using a suitable roller burnishing tool, here a cylindrical roller burnishing roller 20, with a force (rolling force) directed perpendicular to the outer surface 11. In this process, fine chips are removed from the outer surface 11 and, at the same time, the yield point of the material of the housing 5 is locally exceeded, resulting in permanent plastic deformations in the outer surface 11 in the form of circumferential grooves 13. The housing 5 can be mounted on a mandrel 21. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2019 208 063 A1

[0003]

Claims

[1] Battery cell (1) for a battery, in particular a traction battery of a vehicle, - with a housing (5) defining a longitudinal center axis (4), which has a casing (7) extending in a circumferential direction (6) around the longitudinal center axis (4) and has bases (9) at opposite longitudinal ends of the housing (5), - wherein the casing (7) has an outer surface (11) pointing away from the longitudinal center axis (4) and intended for wetting with a casting compound (10), characterized by , that - the outer surface (11) has a surface structure (12) formed by circumferential grooves (13). [2] Battery cell (1) according to claim 1, characterized by , that - the circumferential grooves (13) form circumferential ring grooves which encircle the outer surface (11) completely closed or at least partially in a ring shape. [3] Battery cell (1) according to claim 1 or 2, characterized by , that - the circumferential grooves (13) form circumferential spiral grooves which run around the outer surface (13) in the direction of the longitudinal center axis (4) in a cylindrical spiral shape. [4] Battery cell (1) according to one of the preceding claims, characterized by , that - the circumferential grooves (13) are arranged uniformly distributed relative to one another in an axial direction (14) aligned parallel to the longitudinal center axis (4). [5] Battery cell (1) according to one of the preceding claims, characterized by , that - the circumferential grooves (13) abut one another in an axial direction (14) aligned parallel to the longitudinal center axis (4). [6] Battery cell (1) according to one of the preceding claims, characterized by , that - the circumferential grooves (13) have a groove profile (16) which is wavy in an axial direction (14) aligned parallel to the longitudinal center axis (4). [7] Battery cell (1) according to one of claims 1 to 5, characterized by , that - the circumferential grooves (13) have a groove profile (15) which is serrated, in particular sawtooth-shaped or triangular-tooth-shaped, in an axial direction (14) aligned parallel to the longitudinal center axis (4). [8] Battery cell (1) according to one of the preceding claims, characterized by , that - the circumferential grooves (13) are introduced into the outer surface (11) by means of a rolling process or a hydroforming process. [9] Battery cell (1) according to one of the preceding claims, characterized by , that - the circumferential grooves (13) are arranged on at least one section of the outer surface (11), on several separate sections of the outer surface (11) or on the entire outer surface (11). [10] Battery cell (1) according to one of the preceding claims, characterized by , that - the battery cell (1) is a round battery cell (3) that is rotationally symmetrical with respect to the longitudinal center axis (4). [11] Method (17) for producing a battery cell (1), in particular the battery cell (1) according to one of the preceding claims 1 to 10, - in which a housing (5) defining a longitudinal center axis (4) is provided, which has a casing (7) running in a circumferential direction (6) around the longitudinal center axis (4) and bases (9) at opposite longitudinal ends of the housing (5), - wherein the casing (7) has an outer surface (11) pointing away from the longitudinal center axis (4) and intended for wetting with a casting compound (10), - wherein a surface structure (12) is formed on the outer surface (11) by introducing circumferential grooves (13) into the outer surface (11) by means of a rolling process or a hydroforming process. [12] Method (17) according to claim 11, characterized by, that - the circumferential grooves (13) are introduced into the outer surface (11) on at least one section of the outer surface (11), on several separate sections of the outer surface (11) or on the entire outer surface (11) of the outer surface (11) of the casing (7). [13] Method (17) according to claim 11 or 12, characterized by , that - before the formation of the surface structure (12) from circumferential grooves (13), a cleaning step is carried out, during which the outer surface (11) of the casing (7) is freed of impurities by means of a plasma cleaning process, a laser cleaning process or a chemical cleaning process. [14] Method (17) according to one of the preceding claims 11 to 13, characterized by , that - the battery cell (1) is encapsulated by a casting compound (10) at least in the region of the surface structure (12) comprising circumferential grooves (13). [15] Vehicle, in particular an electrically driven motor vehicle, with a battery, in particular a traction battery, which has a plurality of battery cells (1) according to one of the preceding device claims 1 to 10 or a plurality of battery cells (1) produced according to one of the preceding method claims 11 to 14.

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