Method for producing a battery cell

Abstract

The invention relates to a method for producing a battery cell (10), the battery cell (10) comprising a housing. The battery cell (10) comprises an electrochemical cell disposed in the interior of the housing, and the housing comprises a first housing part (12). A first electrically insulating coating (14) is applied at least to the first housing part (12) before the electrochemical cell is inserted into the housing.

Description

[0001] Description

[0002] Process for producing a battery cell

[0003] The invention relates to a method for producing a battery cell according to the preamble of claim 1.

[0004] Battery cells of the type in question have a housing. An electrochemical cell is arranged in the housing. In this case, it is often necessary to provide the housing with an electrically insulating coating. This is particularly the case if the housing or a housing part that is a component of the housing is made of an electrically conductive material, such as a metallic material. In addition to electrical insulation, the coatings applied to such housings or housing parts often also fulfill other functions, such as mechanical protection and / or thermal insulation. When selecting a suitable coating, other aspects may also play a role, for example the suitability for attaching the battery cell by means of an adhesive.

[0005] In practice, the problem with coating the battery cells in question is that they are temperature-sensitive due to the electrochemical cell located inside the battery cell. The temperature of the battery cell must not normally exceed 60°C during the coating process. Furthermore, care must be taken when handling the battery cell to avoid electrical accidents, such as short circuits, since a "live" battery cell must be handled during the coating process and subsequent quality control of the coating.

[0006] These constraints limit the selection of suitable coatings and coating processes. This limits the possibilities for meeting the various coating requirements.

[0007] Therefore, processes for manufacturing battery cells have already been developed in the prior art to better meet the diverse requirements for coatings of such battery cells. For example, DE 102020 111 243 A1 discloses a lithium-ion battery whose housing has different coatings on different surfaces. In this case, a thermally insulating coating is applied to surfaces of the battery housing that, during the intended use of the lithium-ion battery, are adjacent to other batteries. Where the battery is adjacent to a heat-dissipating module housing, however, a thermally conductive coating is applied.

[0008] This is intended to ensure that, in the event of thermal runaway of the battery, heat can be dissipated through certain surfaces, while also minimizing the transfer of heat energy to neighboring batteries through other surfaces. However, the fundamental problem of limited coating options resulting from the electrochemical cell inside the battery remains when applying the individual coatings.

[0009] The invention is therefore based on the object of demonstrating a method for producing a battery cell in which the problems described above do not occur or at least occur to a reduced extent, in particular wherein a wider selection of coating methods is available and / or the execution of the coating method and, if appropriate, a downstream quality control is simplified.

[0010] The object is achieved by a method for producing a battery cell having the features of independent claim 1. The features of the dependent claims relate to advantageous embodiments.

[0011] The method provides that the battery cell has a housing. The housing is in particular a rigid housing, a so-called hard case. In this context, the housing can have an at least substantially cuboidal basic shape. In other words, the battery cell can be a prismatic battery cell. In this case, the housing has in particular two flat sides and four narrow sides, which have a significantly smaller extension in the thickness direction of the cell than the flat sides and the narrow sides in the other extension directions of the cell. The battery cell has an electrochemical cell arranged inside the housing. The electrochemical cell can in particular be a lithium-ion cell. Accordingly, the battery cell is a secondary battery or an accumulator.

[0012] The battery cell can have one or more electrical connection elements for electrically contacting each pole of the electrochemical cell. The electrical connection elements can be arranged, in particular, on the narrow sides of the housing. In particular, two connection elements can be arranged on one narrow side of the housing, or one connection element can be arranged on each of the opposite narrow sides of the housing.

[0013] The housing has at least a first housing part. The first housing part is made of an electrically conductive material, preferably a metallic material.

[0014] The object is achieved in particular by applying a first electrically insulating coating at least to the first housing part before the electrochemical cell is introduced into the housing.

[0015] Because the electrically insulating coating is applied to the housing part before the electrochemical cell is inserted into the housing, the application of the coating has no effect on the electrochemical cell. Therefore, for example, the temperatures associated with the application of the first coating are irrelevant to the electrochemical cell. There is also no risk of electrical short circuits damaging the electrochemical cell during the coating process.

[0016] In particular, after applying the first coating to at least the first housing part and before inserting the electrochemical cell into the housing, an inspection of the first housing part and / or the first coating can be carried out, particularly for quality assurance purposes. This inspection is then also not influenced by the presence of an electrochemical cell inside the housing.

[0017] In particular, the method may provide for the first coating to be an electrochemical coating, a paint coating, and / or a powder coating. This allows for the realization of coatings that have high mechanical requirements. Alternatively and / or additionally, the method may provide for the first coating to be a thermal barrier coating. Such thermal barrier coatings are also referred to as "thermal barrier coatings (TBC)."The method can provide for the thermal barrier coating to be produced by means of electron beam physical vapor deposition (EBPVD), atmospheric plasma spraying (APS), vacuum plasma spraying (VPS), high velocity oxygen fuel (HVOF), electrostatic spray-assisted vapor deposition (ESAVD) and / or direct vapor deposition (DVD).

[0018] The method may provide for a second coating to be applied to the housing after the electrochemical cell has been inserted into the housing. The second coating may serve, in particular, to complete the electrical insulation of the housing in those areas that could not be coated and / or could only be coated inadequately by the first coating.

[0019] The inadequate and / or nonexistent coating may result, on the one hand, from areas of the housing that were not suitable for the process for applying the first coating for technical reasons. It may also be areas of the housing to which the first coating was not applied for cost reasons, for example.

[0020] For example, it may be the case that the first coating is more expensive than the second coating, but offers greater mechanical resistance. In such cases, it makes sense to apply the first coating only to surfaces of the housing that are subject to particularly high mechanical stress, and to coat all those areas where the second coating is sufficient to meet the requirements with the second coating.

[0021] In particular, those parts of the housing for which a coating is only reasonably possible after the electrochemical cell has been inserted into the housing for technical reasons can also advantageously be coated with the second coating. This can, for example, involve transitions between housing parts that are only connected to one another during the insertion of the electrochemical cell into the housing. In this context, the method can provide that after the insertion of at least the fixed components of the electrochemical cell and / or before the application of the second coating, the housing of the electrochemical cell is closed by connecting a second housing part to the first housing part.

[0022] The fixed components of the electrochemical cell include, in particular, the current collectors, which are usually metal foils and serve to conduct the electrical current from the electrodes made of the electrochemically active material of the cell to the electrical connection elements of the battery cell, the electrodes made of the electrochemically active material of the cell itself and / or a separator which separates the anode compartment from the cathode compartment.

[0023] The non-solid components of the electrochemical cell include, in particular, the cell's electrolyte or the liquid portion of the cell's electrolyte. This can, if necessary, be filled into the otherwise sealed battery cell through a separate, sealable filling opening.

[0024] The closing of the battery cell is therefore to be understood in particular as meaning that the battery cell is closed to such an extent that at least the solid components of the electrochemical cell can no longer be removed from the battery cell without it being opened again.

[0025] Sealing the battery cell before applying the second coating offers the particular advantage that the battery cell, and in particular the battery cell housing, is largely finished. Applying the second coating can thus serve, in particular, to complete the necessary electrical insulation measures on the battery cell housing.

[0026] The second coating can, in particular, be a film. As a coating material, films offer the advantage of being comparatively cost-effective, and they can also be applied very precisely to certain areas of the battery cell housing. Due to their geometrically determined shape and the resulting good handling, films offer the particular advantage of being able to coat even those areas of battery cells that are difficult to access with other coating processes. Furthermore, film coatings can be easily applied to battery cell housings in which the electrochemical cell has already been incorporated. The thickness of the film can, in particular, be at least 30 μm and / or a maximum of 150 μm.

[0027] Alternatively and / or additionally, the second coating may be a coating with a multilayer insulating material and / or a plastic. In particular, preformed plastic elements, whose shape can be adapted to the respective area of ​​the battery cell to be coated, can be applied as the second coating. The thickness of the plastic elements can in particular be at least 80 μm and / or at most 500 μm.

[0028] The material of the film and / or the plastic element can be polyester (PET), polyamide (PA), polypropylene (PP) and / or a combination of the above plastics.

[0029] The housing, in particular the first housing part, can have a wall thickness of at least 300 μm and / or at most 1000 μm. In connection with the present method, it has been shown that wall thicknesses in this range, on the one hand, lead to housings that have sufficient stability, in particular in conjunction with the applied coating. On the other hand, it is advantageous not to exceed a certain wall thickness for cost and weight reasons. In particular, the possibility of increasing the mechanical resistance of the battery cell by means of the first coating applied before the electrochemical cell is introduced can reduce the mechanical requirements of the housing itself, in particular of the first housing part. As a consequence, the method also enables weight savings in the battery cell.

[0030] The first housing part can be a housing part that connects two opposite sides of the battery cell. Such a housing part can, in particular, have a cylindrical shape. This can, in particular, be a cylinder with a rectangular cross-section, but alternatively also a cylinder with a circular cross-section.

[0031] The first housing part can, in particular, form the two flat sides and two opposite narrow sides of an at least substantially cuboid-shaped basic shape of the battery cell, at least for the most part. The sides of the battery cells connected by the first housing part can, in particular, be the sides of the battery cells on which the electrical connection elements for electrically contacting the poles of the electrochemical cell of the battery cell are arranged.

[0032] Such a cylindrical shell-shaped housing part provides a comparatively large portion of the battery cell's surface area. Furthermore, it is a housing part associated with a relatively low level of complications regarding the suitability of the surfaces to be coated for the application of the first coating.

[0033] Alternatively and / or additionally, the first housing part can be a housing part that has a cup-shaped configuration. Accordingly, it is in particular a housing part that at least predominantly forms two flat sides and three narrow sides of the housing of a battery cell that has an at least substantially cuboidal basic shape.

[0034] Such a cup-shaped housing part has, in particular, an open side through which the electrochemical cell can be inserted. The method provides, in particular, that the first housing part is closed by connecting it to a second housing part, which forms this side of the housing.

[0035] Such a cup-shaped housing part provides a comparatively large portion of the battery cell's surface area. Furthermore, it is a housing part associated with a relatively low level of complications regarding the suitability of the surfaces to be coated for the application of the first coating.

[0036] The second housing part can, in particular, be a housing part that forms one of two opposite sides of the battery cell. The housing part can be designed to be at least substantially flat. The second housing part, in particular, forms one of the opposite sides of the battery cell on which at least one electrical connection element for electrically contacting a pole of the electrochemical cell of the battery cell is arranged.

[0037] Accordingly, the second housing part can in particular have one or two electrical

[0038] A second housing part with two electrical

[0039] Connection elements are used in particular in conjunction with a cup-shaped first housing part. A second housing part with an electrical connection element is used in particular with a cylindrical first housing part, in particular in conjunction with a further second housing part with an electrical connection element. In this case, the further second housing part forms in particular the side of the battery cell opposite the second housing part.

[0040] The method may provide that the first coating and / or the second coating have a thickness of at least 50 μm and / or at most 300 μm. It has been shown that coatings in this thickness range are particularly well suited for providing sufficiently mechanically resistant coatings without excessive consumption of coating material.

[0041] The second coating can be applied to a region of the housing surface that encompasses at least a partial region of the surface of the second housing part. This is advantageous given that the first coating has already been applied to the first housing part. Therefore, it is advantageous to use the second coating primarily for the protection, in particular for electrical insulation, of the second housing part.

[0042] In this case, however, the second coating can also extend over the first housing part; in particular, the second coating can also extend over areas of the first housing part that are already coated with the first coating. In this way, on the one hand, a local reinforcement of the coating can be achieved at specific locations, and on the other hand, continuous electrical insulation can be achieved, particularly at the transitions between the first coating and the second coating, by overlapping the two coatings where they adjoin one another.

[0043] The region of the surface of the housing to which the second coating is applied can in particular comprise at least a partial region of a connection between the second housing part and the first housing part. Alternatively and / or additionally, the region of the surface of the housing to which the second coating is applied can comprise at least a partial region of a connection between the second housing part and an electrical connection element for electrically contacting a pole of the electrochemical cell. Such connection regions between housing parts or between housing parts and electrical connection elements can in a particularly advantageous manner only be coated after the assembly of the battery cell has been largely completed. This is due in particular to the fact that the corresponding connections are only created or formed during assembly.previously applied coatings would be impaired or even destroyed by the formation of the connection.

[0044] The latter is the case, for example, when the housing parts are welded together or when electrical connection elements are welded to housing parts. A previously applied coating is usually damaged or destroyed in the area of ​​the weld seam, so the subsequent application of the second coating after welding is particularly advantageous in such areas.

[0045] Advantageously, a plurality of battery cells produced according to the method described above can be combined to form a battery module. The coatings of the battery cells can be optimized using the method described above. In this way, battery cells can be produced which, due to the optimized coatings, are particularly well suited for being combined into battery stacks and mechanically connected to one another. The improved electrical insulation of the battery cells, which can be achieved using the coatings, also enables the interconnection of a large number of battery cells with the correspondingly high voltages and / or currents that arise in this case.

[0046] The battery cells produced by the method described above and / or battery modules produced from these battery cells, which contain a plurality of battery cells produced by the method described above, can advantageously be used to supply electric drives of electrically powered motor vehicles with electrical energy.

[0047] High performance requirements are placed on the drive systems of electric vehicles. Furthermore, the batteries must meet stringent requirements regarding their service life and protection against environmental influences. There are also stringent safety requirements to minimize the risk to vehicle occupants, for example, in the event of a thermal runaway. All of these goals can be achieved more effectively through improved coatings on individual battery cells than with current battery cells or the processes used to manufacture them.

[0048] Further practical embodiments of the invention are described below in conjunction with the drawings. They show:

[0049] Fig. 1 shows an exemplary method for producing a battery cell according to a first embodiment,

[0050] Fig. 2 is a schematic representation of a method for producing a battery cell according to a second embodiment.

[0051] The method for producing a battery cell 10 shown in Figure 1 starts with a first housing part 12 shown in Figure 1A. A first electrically insulating coating 14 is first applied to the first housing part 12. The result of applying the first coating 14 to the first housing part 12 is shown in Figure 1B.

[0052] In the case of the first embodiment shown in Figure 1, the first housing part 12 is cup-shaped and forms the two surface sides 16 and three narrow sides 18 of the at least substantially cuboid basic shape of the exemplary prismatic battery cell 10.

[0053] The electrochemical cell is inserted into the first housing part 12 provided with the first coating 14, and the housing of the battery cell 10 is closed by connecting a second housing part 20 to the first housing part 12. The second housing part can be flat, as in the example shown, and can comprise two electrical connection elements 22, each for contacting a pole of the electrochemical cell arranged inside the battery cell 10. The resulting battery cell 10 is shown in Figure 1C.

[0054] Figure 2 shows an alternative embodiment. The first housing part 12 shown in Figure 2A has a cylindrical shell-like basic shape with a rectangular cross-section. The first housing part 12 forms the flat sides 16 and two opposite narrow sides 18 of the cuboid-shaped basic shape of the resulting prismatic battery cell 10. The first coating 14 is first applied to the first housing part 12 shown in Figure 2A. The first housing part 12 with the applied first coating 14 is shown in Figure 2B.

[0055] After applying the first coating 14 to the first housing part 12, the electrochemical cell is inserted into the first housing part 12. As in the example shown, the method may provide for the first housing part 12 to be connected to two second housing parts 20 and thereby sealed. The result is shown in Figure 20.

[0056] As in the example shown, the second housing parts 20 can each form a narrow side 18 of the at least substantially cuboidal basic shape of the exemplary battery cell 10. Furthermore, the second housing parts 20 can each have an electrical connection element 22 for electrically contacting a respective pole of the electrochemical cell.

[0057] In a further method step, a second coating 24 can be applied to the battery cell 10 depicted in Figure 2C. As in the example shown, the second coating 24 can be applied to regions of the surface of the housing of the battery cell 10 that encompass the connections of the second housing parts 20 to the first housing part 12 and the connection of the second housing parts 20 to the electrical connection elements 22. As in the example shown, the first coating 14 and second coating 24 can overlap in the region where the coatings 14 and 24 adjoin one another. The battery cell 10 with the applied second coating 24 is shown in Figure 2D.

[0058] The features of the invention disclosed in the present description, in the drawings, and in the claims can be essential, both individually and in any combination, for the realization of the invention in its various embodiments. The invention can be varied within the scope of the claims and taking into account the knowledge of the person skilled in the art. List of reference symbols Battery cell First housing part First coating Flat side Narrow side Second housing part Electrical connection element Second coating

Claims

Patent claims 1. A method for producing a battery cell (10), wherein the battery cell (10) has a housing, wherein the battery cell (10) has an electrochemical cell arranged inside the housing, wherein the housing has a first housing part (12), characterized in that a first electrically insulating coating (14) is applied at least to the first housing part (12) before the electrochemical cell is introduced into the housing.

2. Method according to claim 2, characterized in that the first coating (14) is an electrochemical coating, a paint coating and / or a powder coating 3. Method according to one of the preceding claims, characterized in that after the electrochemical cell has been introduced into the housing, a second coating (24) is applied to the housing.

4. Method according to one of the preceding claims, characterized in that after the introduction of at least the solid components of the electrochemical cell and / or before the application of the second coating (24), the housing of the electrochemical cell is closed by connecting a second housing part (20) to the first housing part (12).

5. Method according to one of claims 3 or 4, characterized in that the second coating (24) is a film 6. Method according to one of the preceding claims, characterized in that the housing, in particular the first housing part (12), has a wall thickness of at least 300 pm and / or at most 1000 pm.

7. Method according to one of the preceding claims, characterized in that the first housing part (12) is a housing part, in particular one in the form of a cylinder jacket, which has two opposite sides of the battery cell (10), on which in particular the electrical connection elements (22) for electrical Contacting the poles of the electrochemical cell of the battery cell (10) are arranged, interconnected, and / or a housing part which has a cup-shaped configuration.

8. Method according to one of the preceding claims, characterized in that the second housing part (20) is a, in particular flat, housing part which forms one of two opposite sides of the battery cell (10), on which at least one electrical connection element (22) for electrically contacting a pole of the electrochemical cell of the battery cell (10) is arranged.

9. Method according to one of the preceding claims, characterized in that the first coating (14) and / or the second coating (24) has a thickness of at least 50 pm and / or at most 300 pm.

10. Method according to one of the preceding claims, characterized in that the second coating (24) is applied to a region of the surface of the housing which comprises at least a partial region of the surface of the second housing part (20), in particular wherein the region comprises at least a partial region of a connection of the second housing part (20) to the first housing part (12) and / or a connection of the second housing part (20) to an electrical connection element (22) for electrically contacting a pole of the electrochemical cell.

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