Method for joining and electrically contacting individual thin films of a thin film stack and applications thereof

Abstract

Method for joining and electrically contacting thin films of a thin film stack and use thereof. The invention relates to a method for joining and electrically contacting thin films (18) of a thin film stack (16), wherein at least the following method steps are carried out: a) fixing the thin film stack (16) in a clamping device (46), b) converting the flat, planar thin film stack (16) into a V-shaped (48) bent thin film stack (38), so that c) the flat, planar thin film stack (16) is subjected to a shape change (34) in the direction of the laser beam direction (14), d) thermally joining the thin films (18) by means of a laser beam, which passes through an opening (62) provided in the clamping device (46) and bonds the thin films (18) of the thin film stack (16) firmly to one another by means of a line-shaped connection (42). Furthermore, the invention relates to a clamping device for carrying out the above-mentioned method for joining and electrically contacting thin films (18) of a thin film stack (16) and the use of the clamping device.

Description

TECHNICAL FIELD

[0001] The present invention relates to a method for joining and electrically contacting thin single films of a thin film stack, to a clamping device for fixing a thin film stack and to the use of the clamping device. BACKGROUND

[0002] JP 2000-200594 relates to a battery having a positive electrode and a negative electrode. Furthermore, holders for the negative electrode current collector and the positive electrode current collector are provided, respectively. One end of a copper film at the upper end of the negative cathode is held above the holder of the negative electrode conductor, protrudes above the window, is bent and pressed onto a platen sheet and is then joined in a stoffschlüssiger manner by means of a laser welding method. In this way, it is possible in an advantageous manner to avoid the electrodes from slipping out of the holders, which reduces the reduction in the power of the battery under adverse operating conditions, for example, in the event of vibrations and strong impacts, etc.

[0003] EP 2 308 633 relates to a fixture for laser welding of electrical contacts in photovoltaic cells. The fixture acts on a portion of the photovoltaic cells of a solar module, which are connected to one another by means of a laser welding method.

[0004] A battery cell for a battery or accumulator comprises a cathode, at least one separator, an electrolyte and an anode, which are embodied as thin films. In order to increase the electrical capacity of the individual battery cell, a plurality of such complexes are stacked on top of one another, which is also referred to as a thin film stack, and the cathodes and the anodes are electrically contacted, respectively. The thin film stack formed by the many cathodes and anodes must be electrically connected to one another on the one hand and also mechanically connected to one another on the other hand.

[0005] In the case of large-scale industrial production methods, ultrasonic welding, and also laser beam welding, are applied in order to produce the electrical and mechanical connections.

[0006] The disadvantage of the ultrasonic welding method is the case that small particles can be formed as a result of the process, which can penetrate the separators, which are mostly only a few μm thick, and can thus cause short circuits in the battery cell.

[0007] In the case of laser beam welding, high temperature gradients arise as a result of the melting and solidification of the material in the assembly. This leads to an expansion or upward curvature of the individual thin films of the thin film stack, which usually takes place in the direction opposite to the current conductor during the welding process, opposite to the direction of the laser beam. As a result of this phenomenon, a gap arises between the individual thin films and the current conductor in the case of the thin film stack, which cannot be filled by the molten material, so that a reliable contact is not possible. SUMMARY

[0008] According to the invention, a method for joining and electrically contacting individual thin films of a thin film stack is proposed, which has at least the following method steps:

[0009] a) fixing the thin film stack in a clamping device,

[0010] b) converting the flat, planar thin film stack into a V-shaped, bent thin film stack, such that

[0011] c) the flat, planar thin film stack is subjected to a shape change in the direction of the laser beam direction, i.e. in the direction of the conductor (Ableiter),

[0012] d) and thermally joining the individual thin films of the thin film stack by means of a laser beam, which passes through an opening provided in the clamping device and adhesively connects the individual thin films of the thin film stack to one another by means of a line-shaped connection.

[0013] By means of the method according to the invention, the thermally induced expansion of the individual thin films of the thin film stack is guided by means of the clamping device in such a way that the shape change takes place in the direction of the laser beam direction, i.e. in the direction of the conductor (Ableiter). Furthermore, it can be achieved in an advantageous manner by means of the clamping device that the interspaces present between the individual thin films of the thin film stack during the thermal joining by means of the laser welding method are minimized and the minimized interspace width remains constant during the entire thermal joining.

[0014] In an extension of the method according to the invention, during the execution of the method step d), the individual thin films of the thin film stack clamped in the clamping device are subjected to a shape change by thermal expansion, which shape change takes place in the direction of the laser beam direction.

[0015] In the method according to the invention, during the execution of the method step d), i.e. during the construction of the adhesively secure line-shaped connection, an interspace minimization of the interspace width between the individual thin films of the thin film stack is achieved by means of the clamping device.

[0016] In the method according to the invention, during the execution of the method step d), the thermal expansion of the individual thin films of the thin film stack is guided in the direction of the laser beam direction or directed at the conductor by means of the clamping device.

[0017] In the method according to the invention, an electrical contact is produced in the contact area between the thin film stack and the conductor below the lower individual thin film of the thin film stack.

[0018] Furthermore, in the method according to the invention, the thin film stack half folded up in a V shape by means of the clamping device can be covered by means of the clamping device and the shielding surface constructed there, such that said thin film stack half is protected from impurities and from particles and the like entering from the outside by means of the laser welding method when the adhesively secure joining method is executed.

[0019] In addition, the invention relates to a clamping device for joining and electrically contacting thin film stacks of thin single films. The clamping device fixes the thin film stack consisting of thin single films such that the gap width between the single films is minimized and the thin film stack is deformed by the clamping device from a flat, planar configuration into a V-shaped thin film stack.

[0020] The clamping device according to the invention is characterized in that the strip-shaped region is delimited by two contact lines which, when the clamping device is placed against the thin film stack, convert the thin film stack into a folded shape, i.e. a V-shape, wherein the contact lines fix the folded thin film stack halves and the folded position of the thin film stack can be maintained during the execution of the bond-secure joining.

[0021] The clamping device is in addition in an advantageous manner provided with shielding faces. These shielding faces are designed such that they cover the folded thin film stack halves so that the thin film stack halves can be effectively protected from impurities entering from the outside.

[0022] In addition, the clamping device is provided such that it not only deforms the thin film stack and fixes the thin film stack in a folded V-shaped configuration, but in addition the strip-shaped region at the lower end of the clamping device has an opening. The opening of the clamping device can be configured as a slot as well as a window. The width of the window-shaped opening is between 0.5 mm and 4.5 mm, while the length of the opening in the strip-shaped region can be between 1 mm and 20 mm.

[0023] Furthermore, the clamping device is provided such that the width of the strip-shaped region in which the support-shaped or window-shaped configured opening is located is between 1 mm and 5 mm.

[0024] In addition, the invention relates to the use of the clamping device for fixing a thin film stack consisting of single films when manufacturing a battery cell of a battery. The use of the clamping device for manufacturing a thin film stack consisting of single films for a battery cell of a battery for an Electric Vehicle (EV) or a Hybrid Electric Vehicle (HEV) or a Plug-In Hybrid Electric Vehicle (PHEV) according to the proposed method is also described.

[0025] Advantages of the invention

[0026] In an advantageous manner, it can be achieved in the use of the solution according to the application that, by means of the use of the clamping device for fixing the thin-film stack, the thermal expansion of the material occurring as a result of the thermal influence during the laser beam welding process can be directed in the direction of the laser beam, i.e. in particular oriented in the direction of the conductor arranged in the lowermost position of the thin-film stack. By this targeted guiding of the thermally induced expansion of the single thin films of the thin-film stack to be joined firmly to one another, the gap width, in particular in the upper region of the thin-film stack, can be minimized. In addition thereto, by means of the solution according to the application, it can be achieved in an advantageous manner that the gap width is kept minimized at all times during the laser welding process when manufacturing the firmly bonded joint, so that under optimum conditions a firmly bonded, preferably linear, connection can be produced in the bottom of the V-shaped deformed thin-film stack fixed in the clamping device.

[0027] By means of the solution according to the application, the gap formed between the single thin films when manufacturing the firmly bonded connection can be minimized, kept minimized and a reliable contact ensured.

[0028] The clamping device is a substantially V-shaped device which deforms the flat, planar thin-film stack consisting of single thin films in such a way that the thin-film stack is deformed in a V-shape. If the V-shaped deformed thin-film stack is clamped in the clamping device, the V-shape is maintained and the thermal expansion of the material of the single thin films is directed, i.e. directed downwards, in the direction of the laser beam when the laser beam is applied. During the execution of the laser beam operation, the gap width is kept minimized, so that a firmly bonded connection of ideally linear configuration is configured in the thin-film stack to be mechanically and electrically contacted.

[0029] By means of the clamping device according to the application, the shape of the thermal input caused by the heat can be directed in a targeted manner into the thin-film stack, which is particularly advantageous for the gap width between the single thin films; i.e. the gap width is minimized and kept substantially constant, so that in mass production the output quantity of good parts can be significantly increased, which of course significantly reduces the production of very undesirable rejects. BRIEF DESCRIPTION OF DRAWINGS

[0030] The application is further described below with reference to the drawings.

[0031] wherein:

[0032] Figure 1.1 a thermal joining of a thin-film stack and the upward arching of the single thin films occurring there,

[0033] Figure 1.2 a thermal joining of the single thin films of a thin-film stack in the sense of the method according to the application,

[0034] Figure 2a schematic representation of a clamping device and a V-shaped deformed film stack consisting of a single film above the conductor is shown,

[0035] Figure 3 a side view of the clamping device is shown, which acts on a film stack to be joined and to be electrically contacted,

[0036] Figure 4 a top view of the clamping device according to Figure 3 is shown,

[0037] Figure 5 a further side view of the clamping device according to the application is shown,

[0038] Figure 6 a top view of the here rectangularly configured openings in the strip-shaped region is shown, and

[0039] Figure 7 a simulation of the shape change is shown. DETAILED DESCRIPTION

[0040] From the illustration according to Fig. 1 a flat, planar film stack 16 consisting of a single film 18 is known, which is joined and electrically contacted by means of a laser beam 12.

[0041] From the illustration according to Figure 1.1 it is known that a laser beam source 10 generates a laser beam 12, which impinges on the film stack 16 with a laser beam direction 14. Figure 1.1 The film stack 16 shown in Fig. 1 comprises a number of single films 18. These single films 18 are film-like films of several μm thickness, which are made as cathodes, separators or anodes and which are essentially embodied as film-like. The single films 18 of the film stack 16 are stacked on top of one another; between the single films 18 there is a gap width. As is known from the illustration according to Figure 1.1 the laser beam 12 generated by the laser beam source 10 impinges on the upper side of the film stack 16 and there produces an upwardly arched uppermost single film 28. The reason for this is that the material of the uppermost single film 18 is suddenly heated by the impingement of the laser beam and thus thermally expands, which leads to Figure 1.1 the upwardly arched uppermost single film 28 shown in Fig. 1. As a result, a gap formation 32 occurs, which is extremely disadvantageous in terms of the production of electrical contacts.

[0042] Below the film stack 16 to be joined and to be electrically contacted is a conductor 20, which is schematically represented.

[0043] From the illustration according to Figure 1.2As can be seen from the diagram, a laser beam 12, also generated by the laser beam source 10, strikes the thin film stack 16 in a direction 14, the stack consisting of a plurality of stacked single thin films 18. Figure 1.2 In the schematically reproduced illustration, the single film 18 is constructed with a corresponding single film thickness 24 of a few μm.

[0044] If the laser beam source 10 emits a laser beam 12 in the laser beam direction 14, the aim is to achieve an initial flatness and a shape change 34 for the flattened thin film stack 16. The shape change 34 in the laser beam direction 14 should be performed as much as possible to minimize the gap width between the individual thin films 18. Figure 1.2 The image shows a deformation of the thin film stack 16, wherein the wavy protrusions of the entire thin film stack 16 extend in the direction of the contact region 22 with the conductor 20, as shown in the figure. Figure 2 As described in more detail in the illustration.

[0045] Figure 2 The initially flat and flatly constructed film stack is shown deformed in a V-shape 48, thereby forming a folded half of the film stack 44 relative to the axis of symmetry.

[0046] According to Figure 2 In the illustration, an initial flat and flat film stack 16, composed of single thin films 18 that are to be electrically contacted with each other, is fixed by a clamping device 46 and deformed to form a V-shape 48 and a folded half 44 of the film stack relative to the clamping device 46, as shown in Figure 2 As shown in the diagram, a laser beam 12 emitted by a laser beam source 10 passes through a clamping device 46 (shown only schematically here) at the center and engages the bent single films 18 arranged vertically on top of each other in the bent film stack 38.

[0047] According to Figure 1.1 The illustration (in which the shape change 30 of the thin film stack 16 is performed opposite to the laser beam direction 14) is the opposite of what is shown in the diagram, from according to Figure 2 As can be seen from the illustration, the bent film stack 38 undergoes a shape change 34 in the direction toward the conductor 20, i.e., in the laser beam direction 14, due to the thermal deformation of the single film 18 when struck by the laser beam 12, both by the clamping device 46 and by the clamping device 46. Since the uppermost single films 18 and 28 of the film stack 16 are fixed by the clamping device 46, the uppermost single film 18 of the film stack 16 cannot be formed in the direction of the laser beam 12. Figure 1.1 The upward arch shown; more precisely, the shape changes 34 according to Figure 2The illustration shows the laser beam direction 14 and applies to all the individual films 18 of the bent film stack 38. Furthermore, the lowermost individual film 18 of the bent film stack 38 is firmly bonded to the upper side of the conductor 20 (shown only schematically here) within the contact area 22. During the laser welding process of the film stack 16 clamped in the clamping device 46, linear connections 42 occur between the individual films 18, with these linear connections occurring on a vertical line 40. At the lowest point of the vertical line 40, i.e., in the contact area 22 with the conductor 20, a firm bond is achieved between the lowermost film 76 of the bent film stack 38 and the upper side of the conductor 20, thus forming an electrical contact there.

[0048] Since the single film 18, which has a thickness of a few μm, is fixed in the vertical direction by the clamping device 46 during the laser beam bonding process, the gap 36 that produces a gap width between the single films 18 during the laser welding process is minimized, thereby ensuring a safe and reliable process for constructing a firmly bonded joint and electrical contact.

[0049] Figure 3 A front view of the clamping device is shown, which holds the bent film stack 38.

[0050] From the basis Figure 3 As shown in the illustration, the clamping device 46 has a substantially V-shaped configuration. The clamping device 46 is characterized by including two inclined shielding surfaces 74 that turn into a narrower strip region 54 at the first contact line 50 and the second contact line 52, respectively. An opening 62 (see illustration) is formed within this strip region 54, which extends from the bottom of the clamping device 46 into the drawing plane. Figure 4 (Top view). A bent film stack 38 is fixed below two contact lines 50 and 52. Within this bent film stack 38, individual films 18 are arranged vertically to each other in a substantially V-shape. The two contact lines 50 and 52, extending on both sides of the strip region 54, act as clamps for the bent film stack 38 in a clamped state, and ensure that the gap width between the individual films 18 is minimized during the bonding process via the linear connection 42, and the gap minimization 36 remains unchanged as long as the film is bonded firmly. The bonded bonding is achieved when the laser beam 12 emitted from the laser beam source 10 extends in the laser beam direction 14, impacts the bend of the bent film stack 38 through the opening 62 constructed in the strip region, heats the individual films 18 thermally, and causes a shape change 34 in the laser beam direction 14 due to the prestress of the clamping device 36. The bent film stack 38 undergoes directional deformation via the clamping device 46, the shape change 34 being due to the thermal expansion of the material of the single film 18 in the desired direction, i.e., in the laser beam direction 14.Figure 3 The direction of contact area 22 with conductor 20 is shown in the diagram. Ideally, the linear connection 42 of the single film 18 of the bent film stack 38 is obtained by bonding firmly in the bent portion of the bent film stack 38 by means of laser beam 12. The lowermost single film 76 of the bent film stack 38 is connected to the... Figure 3 The upper sides of the conductors (not shown) are bonded together to create electrical contact throughout the entire bent film stack 38. The bonding regions 70 of all the individual films 18 of the bent film stack 38 correspond to the linear connections 42, which create a bonded connection between all the individual films 18 perpendicular to the drawing plane.

[0051] Figure 4 It shows that according to Figure 3 The diagram shows a top view of the clamping device 46.

[0052] from Figure 4 From the top view, it can be seen that the clamping device 46 is divided into several sections. The strip-shaped region 54 is adjacent to two inclined shielding surfaces 74, which are constructed according to... Figure 3 The illustration shows the folded film stacked half 44, which further protects it from particle splashes and contamination, etc. The strip area 54 is based on... Figure 4 The diagram is defined by a first contact line 50 and a second contact line 52. Within the strip region 54, an opening 62 with a groove-shaped or rectangular structure is implemented. This opening 62 is based on... Figure 3 The diagram shows the laser beam 12 emitted by laser beam source 10 passing through and generating light in the laser beam source 10. Figure 3 A linear, firmly bonded connection 42 extends perpendicularly to the drawing plane between the single films 18 of the bent film stack 38. According to... Figure 4 The inclined shielding surface 74 shown in the top view covers the remaining surface, i.e., the folded film stack half 44, and protects it from impurities, particles, and sparks. By constructing an opening 62 in the strip region 54 at the bottom of the clamping device 46, the laser beam 12 acts only on the surface according to… Figure 3 The area of ​​the bent film stack 38 located below the groove-shaped or rectangular extended opening 62.

[0053] The width 56 of the strip region 54 between the first contact line 50 and the second contact line 52 is on the order of 1 mm to 5 mm.

[0054] Figure 5 Another side view of the clamping device 46 is shown.

[0055] From the basis Figure 5 As shown in the diagram, the free spaces 68 are located beside the inclined, extended shielding surface 74 of the clamping device 46. These free spaces 68 are based on... Figure 3The fold of the folded film stack half 44 fills the essentially V-shaped 48 illustrated in the drawing in the area of the opening 62. The shielding face 74 has the function of protecting the folded film stack half 44 from contamination by particles, impurities, etc. and in particular from damaging the individual films 18 extending in the folded film stack half 44 during the construction of the firmly bonded connection in the area of the opening 62.

[0056] The strip-shaped area 54 extending perpendicular to the drawing plane according to Figure 5 has a width 56 of between 1 mm and 5 mm.

[0057] It can be gathered from the illustration according to Figure 6 that the opening 62 in the strip-shaped area 54, i.e. in the bottom of the clamping device 46, can have a rectangular or slot-shaped appearance. The opening 62, whether it is provided in a slot shape or a strip shape, extends within the strip-shaped area 54 with a width 64 which can be between 0.5 mm and 4.5 mm and with a length 66 which can be between 1 mm and 20 mm. The opening 62 is arranged relative to the first edge 58 and the second edge 60 of the clamping device 46 such that it is oriented with an edge distance 72 to the respective edge 58 and 60 of the clamping device 46 on both sides. As already mentioned in connection with Figure 3 and 4 , the strip-shaped area 54 in which the opening 62 is constructed is delimited by the first contact line 50 and the second contact line 52 which serve as a presser for the bent film stack 38 during the execution of the laser beam welding.

[0058] Figure 7 A simulation of the shape change of the bent film stack 38 fixed in the clamping device 46 is illustrated.

[0059] It can be gathered from the simulation according to Figure 7 that, when the laser beam is applied in the middle of the bent film stack 38 clamped in Figure 7 , a deformation of the bent film stack 38 occurs. The shape change 34 of the bent film stack 38 proceeds in the direction of the laser beam 14 as illustrated in Figure 4 . In contrast to the simulation according to Figure 2 , 3and 5. Thereby a thermally induced expansion of the meander thin film stack 38 in the direction towards the upper side of the conductor 20 is achieved. Electrical contact of the lowermost single thin film 18 of the meander thin film stack 38 to the upper side of the conductor 20 occurs. In the case of a shape change 34 in the direction of the laser beam 14, said shape change 34 is achieved in the direction of the laser beam, wherein the angle which the V 48 of the meander thin film stack 38 has during the process changes slightly during the laser beam welding. It is important that this shape change 34 is oriented by the clamping device 46 so as to target the upper side of the conductor 20, so that in the contact area 22 with the meander thin film stack 38 and with the upper side of the conductor 20 a robust electrical contact can be produced by the laser welding method.

[0060] The application is not limited to the embodiments described here and aspects highlighted therein. Rather, various modifications can be made within the scope of the claims specification, which are within the scope of the skilled person.

Claims

1. Method for joining and electrically contacting thin single films (18) of a thin film stack (16), the method having at least the following method steps: a) fixing the thin film stack (16) in a clamping device (46), b) converting the flat, planar thin film stack (16) by means of the clamping device (46) into a V-shaped (48) bent thin film stack (38) such that c) the flat, planar thin film stack (16) is subjected to a deformation in the direction of the laser beam direction (14), d) thermally joining the single films (18) by means of a laser beam which passes through an opening (62) implemented in the clamping device (46) and impinges on the bend of the bent thin film stack (38) and adhesively connects the single films (18) of the thin film stack (16) to one another by means of the line-shaped connection (42). During the execution of the method step d), the single films (18) of the thin film stack (16) clamped in the clamping device (46) are subjected to a change in shape (34) in the laser beam direction (14) by thermal expansion. During the execution of the method step d) in the clamping device (46), a gap minimization (36) of the gap width between the single films (18) is achieved. During the execution of the method step d), the thermal expansion of the single films (18) of the thin film stack (16) is directed by the clamping device (46) in the laser beam direction (14) towards the conductor (20). Below the lowermost single film (76) of the thin film stack (16), an electrical contact is achieved in the contact area (22) between the thin film stack and the conductor (20).

2. The method of claim 1, wherein, The folded thin film stack half (44) is protected from contamination by the shielding face (74) of the clamping device (46).

3. The method of claim 1, wherein, The clamping device (46) fixes the thin film stack (16) such that the gap width between the single films (18) is minimized and the clamping device (46) deforms the thin film stack (16) into a V-shape (48).

4. The method of claim 1, wherein, The clamping device has a strip-shaped area (54) which is delimited by two contact lines which fix the folded thin film stack half (44).

5. The method of claim 1, wherein, The clamping device has a shielding face (74) which covers the folded thin film stack half (44).

6. The method of claim 1, wherein, The strip-shaped area (54) has an opening (62).

7. Clamping device (46) for carrying out the method according to any one of the preceding claims 1 to 6, characterized in that The opening (62) is implemented in strip shape.

8. The clamping device (46) according to claim 7, characterized in that The width (64) of the opening (62) is between 0.5 mm and 4.5 mm and the length (66) of the opening (62) is between 1 mm and 20 mm.

9. The clamping device (46) according to claim 7, characterized in that The width (56) of the strip-shaped area (54) is between 1 mm and 5 mm.

10. The clamping device (46) according to claim 8, characterized in that 14. Use of a clamping device (46) according to any one of claims 7 to 13 for fixing a thin film stack (16) composed of single films (18) when manufacturing a battery cell of a battery.

11. The clamping device (46) according to claim 10, characterized in that 15. Use of a clamping device (46) according to any one of claims 7 to 13 for manufacturing a thin film stack (16) composed of single films (18) for a battery cell of a battery of an electric or hybrid electric vehicle.

12. The clamping device (46) according to claim 10, characterized in that 16. Use according to claim 15, wherein the hybrid electric vehicle comprises a plug-in hybrid electric vehicle.

13. The gripping device (46) according to claim 8, characterized in that ​ ​ ​ ​

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