Assembly process for a battery cell and battery cell

Abstract

A mounting procedure for a battery cell (1) is described. In this procedure, - a first rectangular electrode stack (60) and a second rectangular electrode stack (62) are provided, each having a contact ridge (68, 70) projecting parallel to the plane of the respective electrode stack (60, 62) on opposite edges (64, 66), - a first cover assembly (30) associated with one contact bridge (68) and a second cover assembly (32) associated with the other contact bridge (70) are provided, each cover assembly (30, 32) having a current collector connection device (44, 46) which, in the intended assembly state, has contact surfaces (48, 50) aligned parallel to the plane of the respective electrode stack (60, 62) for the contact bridges (68, 70), and - the first electrode stack (60) and the second electrode stack (62) are placed from opposite sides perpendicular to the plane of the surface with the contact ribs (68, 70) against the corresponding contact surfaces (48, 50) and fixed to these to form a cover stack assembly (80).

Description

[0001] The invention relates to an assembly method for a battery cell. Furthermore, the invention also relates to a battery cell, in particular one manufactured using the assembly method according to the invention.

[0002] Modern motor vehicles are often designed as either partially electric (also known as hybrid) or fully electric vehicles. In the first case, the vehicle has an internal combustion engine and an electric motor to assist it and / or for driving modes with reduced load requirements. In the second case, the vehicle (without an internal combustion engine) is equipped only with an electric motor. In both cases, however, the vehicles have traction batteries that, as (rechargeable) energy storage devices, provide the necessary energy for the respective electric motor.

[0003] Such traction batteries are typically made up of a large number of (individual) battery cells that are interconnected to provide the required power. Common battery cell designs include pouch cells, prismatic cells, and (circular) cylindrical cells. In the case of pouch cells, the cell components (electrodes, separators, electrolyte) are packaged in a bag-like casing made of a film. In the case of the other two cell types, the casing is usually rigid (compared to the pouch cell), being cuboid in the case of the prismatic cell and tubular in the case of the cylindrical cell.

[0004] Battery cells are typically developed and designed from the electrodes towards the outer casing. Electrode materials and suitable electrolytes are currently the subject of intensive research, for example, to replace lithium and / or other materials with those offering more suitable energy storage potential and / or lower environmental hazards. The desired (or specified) performance of the battery cell also requires a corresponding size (volume and / or area) of the electrodes, which then need to be housed within a casing.

[0005] However, this results in tolerance chains that can lead to comparatively large tolerance values ​​at the interfaces between the battery cell and the outside, and consequently to problems. Such problems include rejects due to tolerance exceedances in assembly components (e.g., the finished battery cell) or even in intermediate assemblies. US 2016 / 301046 A1, for example, describes how different tolerances in the assembly of a battery cell are to be compensated for by positioning electrode packs on one side in the same position and embedding them (to different depths) in a plastic resin on the opposite side, which then provides a holding function.

[0006] From DE 10 2022 106 551 A1, a battery cell is known in which two electrode stacks are installed in a common housing, in particular wherein contact tabs of the electrode stacks project in the surface direction of the respective electrode stack and are contacted perpendicular to the surface direction with a contact element. CN 2 12 571 193 U describes a comparable battery cell. CN 2 17 158 382 U also shows a battery cell with two electrode stacks.

[0007] The invention aims to enable improved dimensional accuracy of battery cells.

[0008] This problem is solved according to the invention by an assembly method for a battery cell having the features of claim 1. Furthermore, this problem is solved according to the invention by a battery cell having the features of claim 8. Advantageous and partly inventive embodiments and further developments of the invention are set out in the dependent claims and the following description.

[0009] The assembly method according to the invention serves for the assembly, and in particular the manufacture, of a battery cell. For this purpose, a first rectangular electrode stack and a second rectangular electrode stack are provided according to the method. Both electrode stacks have electrodes, preferably flat ones, and in particular electrodes with opposite electrical polarity (i.e., preferably at least one anode and one cathode). Advantageously, such an electrode stack also has a separator inserted between the individual electrodes and an electrolyte (optionally, the electrolyte is introduced into the electrode stacks later). The two electrode stacks each have a contact ridge projecting parallel to a surface plane of the respective electrode stack on opposite edges. Thus, each electrode stack has a first and a second contact ridge.One of these is specifically assigned to the anode and the other to the cathode, so that a positive pole is formed at one edge and a negative pole at the other. Furthermore, a first cover assembly, assigned to one contact bridge, and a second cover assembly, assigned to the other contact bridge, are provided. Each cover assembly has a current collector connection device which, in its intended assembly state, has contact surfaces for the contact bridges aligned parallel to the plane of the respective electrode stack. The first and second electrode stacks are placed against the corresponding contact surfaces from opposite sides, perpendicular to the plane of the electrode stack, and fixed in place, thus forming a cover-stack assembly.

[0010] The battery cell according to the invention is preferably manufactured according to the method described herein and below and thus exhibits the same physical characteristics and advantages described in the method for the battery cell and its components. The battery cell therefore comprises the first rectangular electrode stack and the second rectangular electrode stack, each having a contact ridge projecting parallel to the plane of the respective electrode stack on opposite edges. Furthermore, the battery cell comprises the first cover assembly, which is associated with one contact ridge, and the second cover assembly, which is associated with the other contact ridge.Each cover assembly has a current collector connection device which, in its intended assembly state, has contact surfaces for the contact bridges aligned parallel to the plane of the respective electrode stack. Furthermore, the first and second electrode stacks rest against the corresponding contact surfaces from opposite sides, perpendicular to the plane of the surface, and are fixed to these surfaces to form the cover-stack assembly.

[0011] By connecting the electrode stacks to the contact surfaces perpendicular to their plane, it is possible to compensate for existing manufacturing tolerances, at least in one longitudinal direction (i.e., between the two cover assemblies). In particular, the contact ridges and contact surfaces overlap and are preferably dimensioned such that typical tolerances can be absorbed (compensated). In contrast, with a frontal (especially a butt joint) attachment of the electrode stack contact elements to the contact surfaces, existing tolerances would accumulate and, in the worst case, be exacerbated. The overlapping mounting of the contact ridges on the contact surfaces, however, allows for displacement relative to one another, thus enabling tolerance compensation.In particular, if the electrode stacks vary in length, the contact surfaces can "compensate" for this difference in length by varying the overlap of the contact surfaces with the contact bridges between individual combinations ("pairings").

[0012] In particular, to simplify the pre-setting of external or connection dimensions (preferably in the direction between the two edges carrying the contact ribs), the two cover assemblies are placed in a manufacturing jig according to the invention before being connected to the two electrode stacks. The manufacturing jig preferably defines a distance between the two cover assemblies, especially between a first external contact surface of the first cover assembly and a second external contact surface of the second cover assembly. The assembly jig thus expediently serves to facilitate handling during assembly, particularly the spatial and dimensional alignment of the two cover assemblies with respect to the electrode stacks. Therefore, the manufacturing jig is merely an aid for assembling the battery cell and thus does not constitute a component of the battery cell itself.

[0013] Furthermore, the first electrode stack is placed from a top side onto an associated pair of contact surfaces of the first and second cover assemblies - which are positioned particularly in manufacturing theory - and the second electrode stack is placed from a bottom side onto another associated pair of contact surfaces of the first and second cover assemblies.

[0014] Advantageously, the electrode stacks are then mechanically pre-fixed to the contact surfaces, at least in the area of ​​the contact bridges, using hold-down clamps. Furthermore, according to the invention – particularly after pre-fixation using the hold-down clamps – the contact bridges are spot-welded to the contact surfaces, especially by laser beam welding.

[0015] Furthermore, the contact bridges are subsequently welded to the contact surfaces in a line, particularly by laser beam welding, following pre-fixation or spot welding. Specifically, the contact bridges are welded to the contact surfaces transversely to the longitudinal extent of the electrode stacks and across their entire width. This creates a mechanically stable connection.

[0016] According to a convenient variant of the process, the two electrode stacks are covered and, in particular, held in place on the manufacturing jig by means of welding shields before a welding step. The welding shields are, in particular, plate-like elements that cover the electrode stacks during the corresponding assembly step and preferably have a welding window through which the welding of the associated contact bridge (preferably by laser beam welding) takes place on the contact surface. Preferably, the aforementioned hold-down devices are also inserted through these welding windows, by means of which the contact bridges are locally pressed against the contact surfaces. In particular, one welding shield is applied to the upper electrode stack from the top and another to the lower electrode stack from the bottom.

[0017] According to a preferred method embodiment, the lid-stack assembly is inserted into a cup-shaped housing which has a housing base with a window molded into it. This window is closed by the second lid assembly.

[0018] Advantageously, the window has a rebated frame edge (in other words, a frame with a stepped edge). The second cover assembly has a rebated closing edge that overlaps the rebated frame edge during assembly in the housing. During assembly of the cover stacking assembly in the housing, length tolerances are compensated for by a longitudinal displacement of the cover stacking assembly within the overlap of the frame edge and the closing edge. In other words, due to the two stepped edges, the second cover assembly can be displaced, at least slightly, within the wall thickness of the housing base to compensate for or at least reduce tolerances in this displacement direction.

[0019] According to a preferred embodiment, the closing edge (of the second cover assembly) is tightly welded to the frame edge (of the housing base window) by means of laser beam welding. In particular, the laser beam is aligned parallel to the insertion direction of the cover stack assembly. Specifically, partial surfaces of the two edges that are parallel to the insertion direction and parallel to each other, as well as adjacent to each other, are welded together.

[0020] In the event that the lid stacking assembly is inserted into the cup-shaped housing, the first lid assembly (particularly with regard to its dimensions perpendicular to the insertion direction) is dimensioned such that, when installed in the housing, it aligns with the cup rim opposite the window. Preferably, the first lid assembly is (or is) positioned at least partially on the inside of the cup rim. That is, in this case, the lid assembly is dimensioned correspondingly smaller, so that the cup rim surrounds or engages the lid assembly on the outside. This advantageously allows longitudinal tolerances (especially in addition to the overlap of the housing base with the second lid assembly) to be further compensated for by shifting the lid stacking assembly at least slightly within the housing (and then fixing it in place).Preferably, the first lid assembly is also tightly connected to the cup rim by means of laser beam welding. This advantageously creates a media-tight encapsulated battery cell.

[0021] The conjunction “and / or” is to be understood here and in the following in particular as meaning that the features linked by means of this conjunction can be formed both jointly and as alternatives to each other.

[0022] An embodiment of the invention is explained in more detail below with reference to a drawing. The drawing shows: Fig. 1. A schematic view of a battery cell in perspective. Fig. 2-4 in view according to Fig. 1. Schematic sequence of assembly steps for the battery cell, Fig. 5 in a schematic partial sectional view VV according to Fig. 3 Two electrode stacks of the battery cell in a manufacturing jig, Fig. 6, Fig. 7 in view according to Fig. 1 schematically further assembly steps, and Fig. Figure 8 shows a schematic detail of the battery cell in a perspective partial section view.

[0023] Corresponding parts and sizes are always marked with the same reference symbols in all figures.

[0024] In Fig. Figure 1 shows a schematic representation of a battery cell 1. The depicted battery cell 1 is a prismatic cell with a cuboid shape. This shape is formed by a housing 4 made of a metal sheet. Several electrodes (at least one electrode pair consisting of a cathode and an anode) are arranged in the housing 4, separated by a separator material and combined with an electrolyte. The cathodes and anodes are connected to the outside of the housing 4 via a positive contact terminal 6 and a negative contact terminal 8 (see Figure 1). Fig. 5) contacted and thus brought out. Both contact terminals 6 and 8 are arranged on opposite narrow sides 10 of the battery cell 1 and each form an external contact surface.

[0025] In order to compensate for tolerances in the direction between the narrow sides 10 (i.e. in a longitudinal direction L) already during the assembly of the battery cell 1, an assembly procedure is described below.

[0026] For this purpose, a manufacturing jig 20 (also: assembly jig) is provided (see below). Fig. 2), which is formed by a rectangular frame 22, on the narrow sides of which (comparable to the headboard and footboard of a bed frame) a first support plate 24 and a second support plate 26 are formed. Furthermore, a first cover assembly 30 and a second cover assembly 32 are provided and placed against the first and second support plates 24 and 26, respectively, and held therein by means of retaining brackets 34 and 36 (see Figure 2). Fig. 3).

[0027] The two cover assemblies 30 and 32 accordingly have a first metallic cover plate 40 and a second metallic cover plate 42 (see. Fig. 5) On the inside of this cover plate 40 or 42, an approximately U-shaped contact piece 44 or 46 (or: "current collector connection device") is arranged. The legs of the U of the two contact pieces 44 or 46 project perpendicularly from the respective cover plate 40 or 42 and have contact surfaces 48 or 50 on their outer sides. The legs of the U thus form a kind of support strip, on the contact surface of which the contact surfaces 48 and 50 are formed. The respective contact surfaces 48 or 50 of a contact piece 44 or 46 therefore point away from each other. The contact pieces 44 and 46 are connected through the respective cover plate 40 or 42 to the corresponding contact terminal 6 or 8 and are insulated and sealed from the cover plate 40 or 42.

[0028] As from Fig. As can be seen further in Figure 5, the first cover plate 40 has larger external dimensions, at least a greater width B1, than the second cover plate 42 (with its width B2). This will be discussed in more detail below. As can be seen from Figure 5, the first cover plate 40 has larger external dimensions, at least a greater width B1, than the second cover plate 42 (with its width B2). Fig. As can be seen in Figure 5, the manufacturing jig has 20 contact surfaces 52 and 54 on which the cover plates 40 and 42 can be placed accordingly. These contact surfaces 52 and 54 are offset from each other transversely to the longitudinal direction L.

[0029] Subsequently, a first electrode stack 60 and a second electrode stack 62 are provided. Each of the two electrode stacks 60 and 62 contains at least one pair of the electrodes, separators, and electrolytes described above. The electrode stacks 50 and 62, like the housing 4, are cuboid in shape. On a first narrow side 64 (also: edge), contact tabs associated with the anode and on a second (opposite) narrow side 66 (edge), associated with the cathode, extend from an electrode sheath and are combined to form a first contact ridge 68 and a second contact ridge 70, respectively. Both contact ridges 68 and 70 project in the surface direction (and thus parallel to the longitudinal direction L) of the respective electrode stack 50 and 52.

[0030] The first electrode stack 60 is next inserted into the manufacturing jig 20 from a top side O and its contact ribs 68 and 70 are placed on the contact surfaces 48 and 50 of the two cover plates 40 and 42. Similarly, the second electrode stack 62 is inserted into the manufacturing jig 20 from a bottom side U and its contact ribs 68 and 70 are placed on the contact surfaces 48 and 50 of the "other" U-shaped legs of the two contact pieces 44 and 46 (see figure). Fig. 3-5). Because the contact surfaces 48 and 50, as well as the contact bridges 68 and 70, are aligned parallel to the surface direction and thus to the longitudinal direction L between the two cover plates 40 and 42, tolerance compensation in the longitudinal direction L is possible by allowing the electrode stacks 60 and 62 to be moved at least slightly along the contact surfaces 48 and 50 in the longitudinal direction L. For this purpose, the cover assemblies 30 and 32 are positioned relative to each other in the manufacturing jig 20 so that even with particularly large tolerances of the electrode stacks 60 and 62, the contact bridges 68 and 70 do not completely overlap with the U-shaped legs of the contact pieces 40 and 46.

[0031] Subsequently, welding shields 74 are placed on the manufacturing jig 20 from the top O and the bottom U, which serve on the one hand to pre-fix the electrode stacks 60 and 62 and on the other hand to protect them from radiation and other influences during a subsequent welding process (see Fig. 6) The welding shields 74 each have two narrow slots 76. Hold-down devices 78 are placed through these slots onto the contact bridges 68 and 70 and pressed down, so that the latter are pressed against the contact surfaces 48 and 50 and pre-fixed there. Subsequently, the contact bridges 68 and 70 are spot-fixed to the contact surfaces 48 and 50 (i.e., to the respective U-shaped legs) by means of laser beam welding, and then the hold-down devices 78 are removed. Afterward, the contact bridges 68 and 70 are welded to the contact surfaces 48 and 50 in a line-like fashion through the slots 76 by means of laser beam welding. This forms a cover-stack assembly 80 (see Figure 8). Fig. 5) The welding shields 74 are removed again and the lid stack assembly 80 is taken out of the manufacturing jig 20.

[0032] Optionally, a covering for the two electrode stacks 60 and 62 is added to the lid stack assembly 80.

[0033] In Fig. 7 and Fig. Figure 8 shows in more detail the assembly of the lid stacking assembly 80 in the housing 4. The housing 4 is cup-shaped and has a base 82 on one of its narrow sides 10, into which a window 84 is provided. Through this window 84, the second lid assembly 32 protrudes at least partially after assembly, i.e., after the lid stacking assembly 80 has been inserted into the housing 4 along the longitudinal direction L (also: "insertion direction") (see Figure 8). Fig. 8) Specifically, the contact terminal 6 protrudes through the window 84. On the other narrow side 10, the cup-shaped housing 4 is open, the side walls ending in a rectangular ring-shaped cup rim 86.

[0034] The window 84 is bounded by a "frame edge 88" formed by the housing base 82. This frame edge 88 is rebated, meaning it has a shoulder 90 projecting towards the window 84. A correspondingly opposite edge (referred to as the "closing edge 92") of the second cover plate 42 is rebated, also having a shoulder 94. The two shoulders 90 and 94 form a mutual stop, preventing the cover plate 42 from being pushed through the window 84 from an inner side of the housing 4. However, this design of the frame edge 88 and the closing edge 92 also allows the cover stacking assembly 80 to be moved longitudinally L within the housing 4, at least within the range of one wall thickness of the housing base 82. This allows any remaining tolerances between the cover stacking assembly 80 and the housing 4 to be accommodated or at least partially compensated for.After inserting the cover stacking assembly 80 into the housing 4 (and optionally a corresponding longitudinal alignment to compensate for tolerances), the frame edge 88 is sealed to the closing edge 92 by laser beam welding, with the laser beam being aligned parallel to the longitudinal direction L.

[0035] The first cover plate 40 is dimensioned in its outer dimensions as follows (specifically larger than the second cover plate 42, see below). Fig. 5) that a housing opening surrounded by the cup rim 86 is closed in the intended assembly state - i.e., with the lid stacking assembly 80 inserted. As is shown in particular in Fig.As can be seen in Figure 5, the first cover plate 40 also has a rebated closing edge 96, and is thus designed similarly to the second cover plate 42. However, the closing edge 96 is designed such that the first cover plate 40 abuts against the cup rim 86 when inserted sufficiently deeply into the housing 4. Nevertheless, this design of the first cover plate 40 still allows longitudinal movement of the cover stack assembly 80 within the housing for alignment and tolerance compensation. In this case, laser beam welding is performed with the laser beam oriented perpendicular to the longitudinal direction L. The first cover plate 40 is welded to the housing 4 in a sealing manner.

[0036] Optionally, the first cover plate 40 is designed without a rebate and is dimensioned such that it rests against the cup rim 86 from the inside of the housing 4, specifically against the side walls of the housing 4. This allows for a comparatively large longitudinal displacement within the housing 4.

[0037] The subject matter of the invention is not limited to the embodiment described above. Rather, further embodiments of the invention can be derived by a person skilled in the art from the above description. Reference symbol list 1 battery cell 4 cases 6 Contact connection 8 Contact connection 10 Narrow side 20 Manufacturing Theory 22 rectangular frames 24 Mounting plate 26 Mounting plate 30 Cover assembly 32 Cover assembly 34 retaining brackets 36 retaining brackets 40 Cover plate 42 Cover plate 44 contact pieces 46 contact pieces 48 contact area 50 contact area 52 site area 54 site area 60 electrode stacks 62 electrode stacks 64 Narrow side 66 Narrow side 68 Contact bridge 70 Contact bridge 74 Welding shield 76 slots 78 hold-down devices 80 Lid stacking assembly 82 Case base 84 windows 86 cup rim 88 frame edge 90 shoulder 92 Closing edge 94 Shoulder 96 Closing edge B1, B2 width L Longitudinal direction O Top Underside

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