Method for producing a housing of a battery cell, housing of a battery cell, battery and use of the battery

Abstract

The invention relates to a method for producing a housing (1) of a battery cell, a housing (1) of a battery cell, a battery, and the use thereof. A sheet metal with two sheet metal edges (9, 10) is provided as the starting material, a material taper is introduced into the sheet metal as a predetermined breaking point (12), and the sheet metal is formed into a three-dimensional body such that the two sheet metal edges (9, 10) abut one another. The two abutting sheet metal edges (9, 10) are then firmly connected to one another.

Description

The invention relates to a method for producing a housing of a battery cell, a housing of a battery cell, a battery and the use thereof.In batteries, in particular lithium ion batteries, thermal runaway must be reliably prevented. Thermal runaway refers to a self-boosting, heat-producing process that may occur, for example, due to inadequate cooling or exogenous shocks such as accidents and associated mechanical damage. The thermal runaway can lead to the firing or explosion. Without safety mechanisms, the battery breaks down in an uncontrolled manner.Various safety mechanisms are known from the prior art for preventing uncontrolled rupture of batteries. Thus, AT 518 161 B1 discloses a battery having a plurality of battery cells arranged in a housing. In order to prevent infection of adjacent harmless battery cells during thermal runaway of a defective battery cell, it is provided that at least two battery cells arranged in a cell stack in a row in a stacking direction are arranged in the housing so as to be displaceable in the stacking direction. In each case two adjacent battery cells can be thermally insulated from a predetermined temperature by a protective material, preferably intumescent. The protective material is arranged between adjacent battery cells in such a way that the adjacent battery cells can be displaced away from one another in the stacking direction by the protective material into a fire protection position. This protection requires additional installation space and requires intumescent material.CN 217 848 163 U describes an explosion-proof assembly for a battery housing with a circular vent in one of the housing walls. The housing wall is covered by a plastic plate which covers an outlet opening. The plastic plate has weakened regions and is screwed to the housing wall and sealed off by a sealing ring. Explosion protection with such a safety valve is relatively complicated and requires many individual parts.Another safety valve is disclosed in JP-H11250885 A. It is configured such that a thin portion made of metal is formed in a part of the casing so that the gas in the casing is released by breaking the thin portion when the internal pressure in the casing becomes equal to or higher than a predetermined value (discharge pressure), thereby lowering the internal pressure in the casing. The metal plate is welded, and heat is transmitted to the thin part of the safety valve during welding. As a result, the thin portion of the safety valve which has been work-hardened is difficult to set to a certain valve opening pressure.To solve this problem, US 2012 / 0 114 988 A1 proposes a battery housing having a housing cover. The lid has an ellipsoidal recessed portion in which a V-shaped breaking groove is disposed. In order that the heat introduced during the welding of the housing does not have a disadvantageous effect on the safety valve, the recessed region is flanked by slots which lie opposite the breaking groove and which are intended to deteriorate the heat transfer. The production of a housing with such a housing cover is still comparatively complicated.Object of the InventionThe object of the present invention is to propose a method for producing a housing of a battery cell which avoids the aforementioned disadvantages. It is a further object of the invention to specify a housing for a battery cell and to create a battery with such a battery cell and to show a use.The objects are achieved by a method according to claim 1, by a use according to claim 10 and by devices of claims 5 and 9. Advantageous embodiments are the subject matter of the dependent claims. Advantages and embodiments described in connection with the method also apply analogously to the devices, and conversely advantages and embodiments described in connection with the devices also apply analogously to the methods.The housing according to the invention is produced from a sheet metal. For this purpose, a strip material can first be cut to length. The sheet metal strip (blank) formed from the semi-finished product can be coated. The sheet metal strip is a substantially two-dimensional structure and has two opposite sheet metal edges. The sheet metal strip is cold formed, wherein after the cold forming two sheet metal edges point towards each other and are finally firmly connected to each other. Preferably, the connection is effected by a material bond. Before the sheet metal edges are firmly connected, the sheet metal is provided with a material tapering as a predetermined breaking point.The production of the housing according to the invention is particularly simple because the predetermined breaking point can be introduced with the same process steps with which the sheet metal strip is also formed. Consequently, neither additional components are required nor the machining of different sides, so that the sheet metal strip can turn out to be simpler, so that the tools and the handling can turn out to be simpler. Finally, only one (linear) weld seam is required, which does not require repositioning of the housing blank and thus enables short cycle times.The material tapering is preferably introduced into the preferably still planar sheet metal by stamping. This can thus be introduced directly during the production of the cell housing, bypassing the use of a separate component. In a particularly preferred, but not necessary manner, the material tapering is produced during a production of the cell housing which is implemented by forming, so that this does not require an additional step which is separate from the process. The material tapering can take the form of a longitudinal groove and represents a weakening of the housing, so that it forms a predetermined breaking point. It thus represents a burst contour.In an alternative embodiment, it is provided that the material tapering is introduced into the cell housing by scribing or engraving. By such a chip-removing introduction of the material tapering, the opening pressure of the housing can be adjusted precisely.In one embodiment, it is provided that before the final connection of the sheet metal ends, only cold forming techniques are required for housing production. In particular, stamping, deep-drawing, piercing and bending are provided as cold-forming techniques. Optimum utilization of the material takes place, since virtually no waste is produced. By omitting machining processes, it can be ensured that the housing is not contaminated on the inside, so that cleaning processes and deburring can optionally be dispensed with.The housing is thus produced from a single printed circuit board with the remaining separating point finally connected. Preferably, the separating point is arranged opposite the predetermined breaking point. The maximum distance can ensure that the heat introduced by welding the separating point has only a slight effect on the predetermined breaking point.The method is suitable in principle for producing housings of round cells, but is preferably provided for prismatic cells. In this case, the sheet metal strip is formed in such a way that it describes at the end the envelope of a cuboid (lateral surface) without the two end walls, that is to say describes a cuboid which is open on both end sides. The edges of the cuboid can be rounded for process technology reasons. The body thus formed is also referred to below as a square tube.Preferably, two sheet metal ends of the sheet metal formed into the square tube are connected to one another by a welding point. The welding point can be a weld seam or one or more welding points. Particularly preferably, the predetermined breaking point and the welding point are arranged on different side surfaces of the square tube.The predetermined breaking point can be formed as a longitudinal groove. In one embodiment, it extends parallel to the length of the square tube. It is advantageous if it is spaced apart from the end faces. This ensures that the housing does not burst accidentally anywhere along its entire length. As a result, on the one hand, any material can escape from the end walls, so that their connection is less stressed, and on the other hand, the material can be collected in a common chamber, which can extend transversely over a plurality of battery cells. The width of the chamber can be limited to the length of the predetermined breaking points, and its volume can be matched to the total number of battery cells to be secured.Preferably, the longitudinal groove extends over 10% to 30% of the distance between the end faces of the housing.The two opposite open end sides of the housing can subsequently be closed by sheet-shaped end covers, i.e. after the forming of the metal sheet and the welding of the two ends of the metal sheet to form a jacket, so that the battery cell can be formed to form a pressure chamber. Accordingly, the end covers can also be connected to the housing in a materially integral manner. The battery cell thus comprises at least the casing and the parts closing the interior of the cup casing, in particular the end covers. The end covers can have a thicker wall thickness than the jacket. The end covers preferably have the electrical contacts of the battery cell.The jacket preferably has a substantially constant wall thickness over the entire circumference of 0.2 to 1 mm, preferably of 0.25 to 0.8 mm, particularly preferably of 0.3 to 0.5 mm.A coating can be arranged on the outer side of the jacket at least in regions. The coating is provided for electrical insulation of the housing. The housing is already provided with a coating or prepared for this purpose in the individual part or in the subassembly, that is to say before the sheet metal is formed into the housing. Methods such as anodizing, coating, painting, gluing, etching, blasting, embossing, brushing or the like are suitable for this purpose. The coating is preferably a UV lacquer.For reasons of readability, the invention has been described on a battery cell. The associated embodiments preferably relate to all battery cells arranged in the battery, wherein the battery cells are arranged next to one another in a so-called stack in the battery housing. The battery cells can be immersion-cooled, that is to say they can be surrounded at least in regions by a dielectric immersion fluid for immersion tempering in the battery housing.In order to realize an optionally desired prestress of the battery cells, in particular during startup or in the new state, elastic elements, such as disk springs, can be used at the ends of the battery cell rows for prestressing the stack.The battery arrangement can be used in various applications, in particular in cars, trucks, buses, construction vehicles, machines or marine applications. The battery arrangement is also to be understood as a battery pack having a plurality of battery cells. The battery arrangement is in particular a lithium-ion accumulator.Brief Description of the DrawingsFurther measures which improve the invention are illustrated in more detail below together with the description of preferred exemplary embodiments of the invention on the basis of the figures, identical or similar components being provided with the same reference sign. They show FIG. 1 shows a perspective partial view of a battery cell according to the invention in a first embodiment, FIG. 2 shows a simplified, perspective view of a second battery cell according to the invention, FIG. 3 shows a perspective partial view of a battery cell according to the invention in a third embodiment, FIG. 4 ashows a schematic representation of a first embodiment of a predetermined breaking point and FIG. 4 bshows a schematic illustration of a second embodiment of a predetermined breaking point.DETAILED DESCRIPTION OF THE DRAWINGSAccording to FIG. 1, a housing 1 for a battery cell for a motor vehicle-not shown here-is at least partially illustrated. Preferably, a plurality of battery cells with housings 1 of the same type form a battery.The housing 1 is provided for a prismatic battery cell and has a jacket 2 made of sheet metal. The sheet from which the housing 1 is formed by forming has a substantially constant thickness of between 0.2 and 1 mm. The jacket 2 is of cuboidal design and has two opposite, wide side faces 3, 4 and two narrow side faces 5, 6 arranged perpendicularly thereto and likewise opposite. The housing 1 is hollow on the inside and can subsequently be fitted over the initially open end faces 7, 8 of the housing 1. After forming the sheet metal and welding the ends of the sheet metal to form the jacket 2, the open end faces 7, 8 can be closed by covers-not shown here-which can be welded to the jacket 2 in order to form the cell can 4 into a pressure container.On the outer side of the jacket 2 there is arranged at least in regions a coating-not shown in detail here-which is designed for electrical insulation and as protection against mechanical stress, for example as a result of vibrations.As FIG. 2 shows, the jacket 2 formed from a previously flat sheet metal strip has two opposite sheet metal edges 9, 10 after the forming. The sheet metal edges 9, 10 are firmly connected to one another by a weld seam 11, wherein the weld seam 11 extends parallel to the longitudinal direction of the side surfaces 5, 6.The weld 11 is arranged in the second narrow side surface 6 as shown in FIG. 2. On the opposite, first narrow side surface 5, a predetermined breaking point 12 in the form of a material tapering is arranged. In the embodiment according to FIG. 2, the predetermined breaking point 12 is a longitudinal groove with a reduced material thickness, which is spaced apart from the end faces 7, 8. In the embodiment according to FIG. 1, the longitudinal groove extends over the entire length of the narrow side surface 5.In the embodiment according to FIG. 3, the housing 1 has further grooves 15, 16. The further grooves 15, 16 can in turn represent predetermined breaking points, but can also relieve the predetermined breaking point 12 or stiffen the housing 1.Finally, FIGS. 4 aand 4 b show different shapes of predetermined breaking points 12. The predetermined breaking point 12 according to FIG. 4 ais designed as a longitudinal groove, and in the predetermined breaking point 12 according to FIG. 4 b, V-shaped depressions adjoin the longitudinal groove, so that the regions adjoining the longitudinal groove form a flap-like closure. In the event of a burst, it can thus be ensured that a larger quantity of gas escapes rapidly, so that the internal pressure falls rapidly.List of reference characters1 Housing 2 Jacket 3 First, wide side surface 4 Second, wide side surface 5 First, narrow side surface 6 Second, narrow side surface 7 First end face 8 Second end face 9 First sheet metal edge 10 Second sheet metal edge 11 Weld seam 12 Predetermined breaking point 13 Rear region 14 Cavity 15 First, further groove 16 Second, further grooveReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedAT 518 161 B1

[0003] CN 217 848 163 U

[0004] JP-H11250885 A

[0005] US 2012 / 0 114 988 A1

[0006]

Claims

Method for producing a housing (1) of a battery cell, characterized in that - a metal sheet with two metal sheet edges (9, 10) is provided as starting material, - a material tapering is introduced into the metal sheet as predetermined breaking point (12), and - the metal sheet is shaped to form a three-dimensional body in such a way that the two metal sheet edges (9, 10) bear against one another, and - the two metal sheet edges (9, 10) lying against one another are firmly connected to one another.Method according to claim 1, characterised in that the predetermined breaking point (12) is introduced simultaneously with a forming step of the planar sheet metal into a three-dimensional body.Method according to claim 1 or 2, characterised in that the predetermined breaking point (12) is introduced into the sheet metal by forming.Method according to claim 1 or 2, characterised in that the predetermined breaking point (12) is introduced by scribing or engraving.Housing (1) for a prismatic battery cell having a predetermined breaking point (12) for thermal passage of the battery cell, characterized in that the housing (1) is formed from a sheet metal formed into a square tube and the predetermined breaking point (12) is formed integrally therewith.Housing according to claim 5, characterised in that the two sheet metal edges (9, 10) of the sheet metal formed into the square tube are connected to one another by a welding point (11), wherein the predetermined breaking point (12) and the welding point (11) are arranged on different side surfaces (5, 6) of the square tube.Housing according to claim 5, characterised in that the predetermined breaking point (12) is introduced into the sheet metal by forming or by scribing or engraving.Housing according to Claims 6 and 7, characterized in that the square tube has two end faces (7, 8) spaced apart by an end face spacing, and in that the predetermined breaking point (12) is formed as a longitudinal groove which extends over 10% to 30% of the end face spacing and is spaced apart from both end faces (7, 8).Battery having an arrangement of a plurality of battery cells arranged one behind the other in a longitudinal direction, each of which has a housing (1) according to Claims 5 to 8, characterized bya common chamber which extends in the longitudinal direction and covers the predetermined breaking points (12).Use of a battery according to claim 9 as a vehicle battery.

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