Method for producing an accumulator and device for producing an accumulator

Abstract

The invention relates to a method for producing an accumulator, having at least one cell stack (4), which is formed by stacked single sheets (6), wherein the cell stack (4) is wrapped with a film (8) using a device (2).

Description

[0001] Description

[0002] Method for producing a rechargeable battery and device for producing a rechargeable battery

[0003] The invention relates to a method for producing a rechargeable battery. Furthermore, the invention relates to an apparatus for producing a rechargeable battery.

[0004] Batteries are widely used to store electrical energy. In some applications, they are composed of multiple battery cells and are also used in the automotive sector. Here, the batteries serve, for example, as so-called drive or traction batteries for powering hybrid or electric vehicles.

[0005] Lithium-ion batteries, i.e., batteries made of lithium-ion cells, are currently of particular interest. A variety of designs are known regarding their precise construction. The production of lithium-ion cells is outlined, for example, in "Heimes, Heiner Hans; Kampker, Achim; Lienemann, Christoph; Locke, Marc; Offermanns, Christian; Michaelis, Sarah; Rahimzei, Ehsan (2018): Production process of a lithium-ion battery cell, Frankfurt am Main, PEM of RWTH Aachen University and VDMA Eigendruck."

[0006] The invention is based on the object of providing an advantageous method for producing a rechargeable battery. Furthermore, the invention is based on the object of providing an advantageous device for producing a rechargeable battery. This object is achieved by a method having the features of patent claim 1 and by a device having the features of patent claim 10. The advantages and preferred embodiments cited with regard to the method are also transferable to the device, and vice versa. Advantageous embodiments with expedient further developments of the invention are specified in the dependent claims.

[0007] The method according to the invention is designed for the production of an accumulator. The corresponding accumulator typically has a number of accumulator cells, wherein such an accumulator cell usually has a cell housing or a cell enclosure. Depending on the application, the accumulator is thus then formed, for example, by a single accumulator cell. Typically, however, the accumulator has several such accumulator cells and generally forms a battery or a battery module. A corresponding battery, in turn, typically has a battery housing, and a corresponding battery module usually has a module housing or a carrier unit for accumulator cells. If the accumulator is designed as a battery, in some cases it has a number of the aforementioned battery modules, i.e. at least one such battery module and typically several.

[0008] Independently of this, the accumulator produced by the method has at least one cell stack formed by stacked individual sheets. If the accumulator is constructed from the aforementioned accumulator cells, each accumulator cell typically has such a cell stack, in particular exactly one. Furthermore, each of these accumulator cells is then preferably designed as a so-called pouch cell.

[0009] Furthermore, the cell stack expediently forms a so-called electrode stack. This means that the cell stack contains layers or stacks of electrode materials. Furthermore, the accumulator is preferably designed as a lithium-ion accumulator. Therefore, the layers or stacks in the cell stack typically comprise an anode material, a separator material, and a cathode material.

[0010] Suitable single sheets for the production of a corresponding cell stack for the aforementioned lithium-ion accumulator and a possible process for the production of such single sheets can be found, for example, in “Heimes, Heiner Hans;

[0011] Kampker, Achim; Lienemann, Christoph; Locke, Marc; Offermanns, Christian; Michaelis, Sarah; Rahimzei, Ehsan (2018): Production process of a lithium-ion battery cell, Frankfurt am Main, PEM of RWTH Aachen and VDMA Eigendruck". The corresponding individual sheets are referred to here as sheets.

[0012] In this specific example, three different sheets are manufactured: anode sheets a, which comprise an anode material, separator sheets b, which comprise a separator material, and cathode sheets c, which comprise a cathode material. To produce a corresponding cell stack, these individual sheets are then conveniently stacked in a sequence abcabc and so on.

[0013] An alternative variant uses single sheets, known as monocells. Such monocell sheets typically comprise an anode material, a cathode material, and a separator material in between.

[0014] Independently of this, the individual sheets have a length, a width, and a thickness. A typical thickness value lies in the range of 0.05 mm to 2.5 mm, and especially in the range of 0.1 mm to 1.5 mm. For length and width, values ​​that are at least a factor of 5 or at least a factor of 10 larger are common.

[0015] A cell stack formed by stacked individual sheets of the type described above is then wrapped with a film during the execution of the method, i.e., the method according to the invention. The method for producing the accumulator thus includes a film-wrapping process step, in which the cell stack is wrapped with the film. This film-wrapping process step is carried out using the device according to the invention, and in particular, is fully automated.

[0016] The device, in turn, i.e., the device according to the invention, is designed to produce the previously described accumulator using the method according to the invention and, in particular, to automatically execute the foil-coating part of the method in at least one operating mode. This automatic execution is typically controlled by a control unit of the device.

[0017] Preferably, the foil-coating process step, and thus the wrapping of the cell stack with foil, takes place in an intermediate step. This intermediate step is performed after a process step in which the individual sheets are stacked to form the cell stack and before a process step in which the cell stack is inserted into a cell housing or cell enclosure.

[0018] Furthermore, the intermediate step is typically performed before a process step in which the cell stack undergoes heat treatment, particularly hot pressing. During the heat treatment, the cell stack is typically laminated into a solid block. In some applications, the film is removed by pyrolysis during the heat treatment.

[0019] Irrespective of this, the film preferably does not form a cell enclosure or a cell housing for the cell stack and also preferably does not form part of such a cell enclosure or such a cell housing.

[0020] Furthermore, a simple film without a coating is preferably used as the film. The film is preferably made of a thermoplastic film, for example a film made of polyethylene. According to an alternative embodiment, a film made of a separator material is used as the film, in particular a film made of the separator material contained in the cell stack. Depending on the application, a film with a thickness or strength in the range 0.05 mm to 0.2 mm is also used. Furthermore, the cell stack is preferably simply wrapped with the film, so that only one layer of the film rests on the cell stack. In particular, multiple wrapping is therefore dispensed with.

[0021] It is also expedient if the cell stack is fed to a film wrapping unit of the device for wrapping with film. In this case, the cell stack is preferably moved against a section of the film that is stretched in a gate plane. The gate plane is defined by an entrance gate of the film wrapping unit.

[0022] The gate plane preferably extends in a vertical direction with respect to the Earth system, or at least to a good approximation in a vertical direction. A good approximation here means that the actual direction preferably deviates from the vertical direction by no more than 30°, more preferably no more than 20° and in particular no more than 10°. In addition, the gate plane extends in a transverse direction transverse to the vertical direction. The cell stack is then more preferably moved in a conveying direction against the section of the film, wherein the conveying direction is preferably directed perpendicularly or to a good approximation perpendicular to the vertical direction on the one hand and perpendicularly or to a good approximation perpendicular to the transverse direction on the other. A good approximation here again means that the deviation is preferably no more than 30°, more preferably no more than 20° and in particular no more than 10°.

[0023] Furthermore, the section of film is preferably stretched by means of a number of rollers of the film-wrapping unit. Typically, at least two supply rollers, also called supply reels, are provided. At least one of these supply rollers is then preferably designed as a driven roller. Depending on the application, at least one deflection roller is also provided. In particular, the number of rollers comprises at least two rollers that are arranged offset from one another in the vertical direction and between which the section of film is guided along the gate plane.

[0024] For wrapping with the film, the cell stack is further preferably moved with a front side of the cell stack in front in the aforementioned conveying direction against the section of the film that is stretched in the gate plane.

[0025] Depending on the application, the section is then moved in the vertical direction as soon as the front of the cell stack reaches the gate level and thus the section. The section is only moved a short distance, typically over a distance that is less than the height of the cell stack, i.e., the vertical extension of the cell stack. Preferably, by moving the section, protruding edges of separator material, i.e., separator ends, of the cell stack are bent in the vertical direction and, in particular, connected to one another.

[0026] Typically, a conveyor line of the film wrapping unit is connected to the entrance gate of the film wrapping unit. The conveyor line is designed to transport the cell stack in the aforementioned conveying direction, at least once the cell stack has been fed through the entrance gate of the conveyor line. In this case, after the cell stack has been moved against the section, the cell stack is then preferably guided into the conveyor line and conveyed further in the conveying direction. The film is then carried along by the cell stack, so that it wraps around the cell stack, particularly in a U-shape.

[0027] A further expedient embodiment is one in which the conveyor line has two conveyor belts arranged one above the other, between which the cell stack is then conveyed. In this case, the two conveyor belts preferably exert pressure on the cell stack, which acts on the cell stack in the vertical direction and against the vertical direction. As a result, the film is firmly pressed against the surface of the cell stack. It is also advantageous if the filming unit and in particular the entrance gate has a slider that can be moved in the vertical direction, in particular along the gate plane. The slider is then preferably moved as soon as a rear side of the cell stack opposite the front side has passed the gate plane, whereby the film is expediently placed around the rear side of the cell stack by the slider.

[0028] In a cell stack developed in this way, the film forms a band with two band ends. The two band ends are then preferably joined together. The joining is preferably achieved by welding, in particular by welding using a heating element.

[0029] A corresponding heating element is typically elongated in the aforementioned transverse direction and formed, for example, by a heating wire. Furthermore, the heating element, namely the first heating element, is formed, for example, on the slide. According to an alternative embodiment, the first heating element is formed on a counterbearing for the slide, against which the slide presses according to the previously described method.

[0030] In an advantageous development, two heating elements are provided, namely the first heating element and a second heating element, whereby both heating elements are typically elongated in the aforementioned transverse direction. Furthermore, they are preferably arranged offset from one another in the aforementioned conveying direction. Both heating elements are then formed, for example, on the slide or on the aforementioned counterbearing. Alternatively, one heating element is formed on the slide and one heating element on the aforementioned counterbearing.

[0031] The first heating element is preferably used to weld the two aforementioned banderol ends together. This then usually also results in the film being separated from a film web that extends between the two aforementioned supply rollers. As a result, the film web is separated into two partial webs. The aforementioned second heating element is then more preferably used to weld the two partial webs back together to form one film web, thereby returning the initial state in which a film section is stretched in the gate plane. The separation of the film from the film web and the welding of the two partial webs together takes place virtually simultaneously by the two heating elements.

[0032] The advantages and further developments described in connection with the method are also to be transferred to the device and vice versa.

[0033] In summary, the idea underlying the method according to the invention and the stacking device according to the invention can also be formulated as follows: When a cell stack or, for short, stack is completely stacked, the stack is pushed against a film curtain. Preferably, one of the film supply reels that stretch the film curtain is driven at the same time, so that the film is wound onto the driven film supply reel and unwound onto the other, but only a short distance, so that the protruding edges of the separators in the cell stack are bent either upwards or downwards by the relative speed. This connects the edges of the separators to one another on the front. When the stack has passed the film curtain far enough that the end is flush with the curtain level, the package transport stops.A slider then moves upwards, taking the film with it, bending the edges of the separators on the other side of the package, and then moving against a heating element that thermally seals the films together. The heating element is preferably designed to create two closely spaced seals, one on the stacking side and the other on the film side. The film is severed between the two seals by strong pressure, creating a closed film curtain with a seal and a film-enclosed package. The closed film curtain, including the seal, is now ready for the next package.

[0034] Further advantages, features, and details of the invention will become apparent from the claims, the following description of preferred embodiments, and the schematic drawings. Therein: Fig. 1 shows a device comprising a gripper and a foiling unit. Fig. 2 shows an enlarged view of the gripper with a cell stack and a receiver of the foiling unit.

[0035] Fig. 3 shows an enlarged view of the gripper and the pickup during a transfer of the cell stack,

[0036] Fig. 4 shows an enlarged view of the pickup and an entrance gate of a conveyor line of the foiling unit with the cell stack at the entrance gate,

[0037] Fig. 5 shows an enlarged view of the entrance gate of the conveyor line with the cell stack after passing the entrance gate,

[0038] Fig. 6 shows an enlarged view of the entrance gate of the conveyor line with the cell stack after passing the entrance gate and the movement of a slider of the entrance gate,

[0039] Fig. 7 shows an enlarged view of the entrance gate of the conveyor line with the cell stack after resetting the slider, and

[0040] Fig. 8 a single sheet of the cell stack.

[0041] Corresponding parts are provided with the same reference numerals in all figures.

[0042] A device 2 described below as an example serves to automatically carry out a foil-wrapping process step, in which a cell stack 4 formed by stacked individual sheets 6 is wrapped with a foil 8. The foil-wrapping process step is part of a method for producing rechargeable batteries (not shown), namely lithium-ion rechargeable batteries, each rechargeable battery having at least one such cell stack 4. The automatic execution is typically controlled by a control unit (not shown) of the device 2.

[0043] The device 2 described here comprises a foil-wrapping unit 10 and a gripper 12. A corresponding embodiment is shown in Fig. 1. Figs. 2 to 7 show enlarged sections of Fig. 1 at various times during the foil-wrapping process. During operation of the device 2 and thus during the foil-wrapping process, the cell stack 4 consisting of stacked individual sheets 6 is fed to the foil-wrapping unit 10 by the gripper 12.

[0044] By way of example, all individual sheets 6 are designed identically. An example of such a single sheet 4 is sketched in Fig. 8. It is designed as a so-called monocell and has a layer of an anode material 14, a layer of a cathode material 16, and an intermediate layer of a separator material 18. The layer of separator material 18 forms two protruding edges, which are referred to below as separator ends 20. In Fig. 8, one of these separator ends 20 protrudes on the left side and one on the right side.

[0045] In addition, the single sheet 6 has two electrically conductive conductor foils 22, one of the conductor foils 22 being in contact with the anode material 14 and the other with the cathode material 16. Both conductor foils 22 each form a so-called conductor tab 26, with the two conductor tabs 26 protruding on opposite sides of the single sheet 6. In Fig. 7, only the conductor tab 24 of the conductor foil 22 protruding from the plane of the drawing on the anode material 14 is visible.

[0046] Several such individual sheets 6 are now stacked one above the other in the cell stack 4, such that all individual sheets 6 in the cell stack 4 are uniformly aligned and oriented. The separator ends 20 protrude on a front side 26 of the cell stack 4 and on an opposite rear side 28.

[0047] To wrap the cell stack 4 with the film 8, the cell stack 4 is then fed to the film wrapping unit 10 by being transferred from the gripper 12 to a receiver 30 of the film wrapping unit 10. This is shown in Fig. 3. Various designs are suitable for the gripper 12. In the case of the design according to Fig. 1, the gripper 12 has two gripping jaws 32 that can be moved towards and away from each other, thus enabling a kind of gripping. The two gripping jaws 32 are then connected, for example in a form not shown in detail, via a telescopic arm to a rotation axis about which the telescopic arm can rotate. The rotation axis, in turn, is mounted, for example, vertically displaceably on a rail.

[0048] In the embodiment shown in Fig. 1, the two gripping jaws 32 are still designed identically and each have a comb-like shape. To form such a comb-like shape, several parallel strips 34 are arranged next to one another. This is clearly visible in Fig. 2.

[0049] The design of the two gripping jaws 32 is adapted to the pickup 30. The pickup 30 is formed by two gripping jaws 36. Each of these gripping jaws 32 is designed like a simple conveyor belt with two drive rollers 38, but instead of a single wide belt, several narrow belts 40 are stretched between the two drive rollers 38 and arranged side by side. As shown, for example, in Fig. 2.

[0050] A gap is left between each belt 40 so that the bars 34 of the gripping jaws 32 of the first gripper 12 can be positioned between the belts 40. This situation is indicated in Fig. 3. Furthermore, the two gripping jaws 36 of the pickup 30 are each pivotally mounted around one of the drive rollers 38, so that they can be moved like the two jaws of a pair of pliers.

[0051] Once the cell stack 4 has been transferred, the pickup 30 conveys the cell stack 4 with the front side 26 leading along a conveying direction 42 toward an entrance gate 44 of the film-wrapping unit 10. The entrance gate 44 defines a gate plane 46 in which, in an initial state, a section 48 of the film 8 is stretched. This situation can be seen in Fig. 1 and Fig. 2. In the exemplary embodiment according to Fig. 1, the gate plane 46 extends in a vertical direction 50 perpendicular to the conveying direction 42 with respect to the earth system. In addition, the gate plane 46 extends in a transverse direction 52 perpendicular to the vertical direction 50 and perpendicular to the conveying direction 42.

[0052] Furthermore, the section 48 of the film 8 is preferably stretched by two pairs of rollers of the film-wrapping unit 10. Two supply rollers 54 form one of the pairs, and two deflection rollers 56 form the other pair. The supply rollers 54 are driven.

[0053] In order to wrap the film 8, the cell stack 4 is now moved with the front side 26 of the cell stack 4 first in the conveying direction 42 against the section 48 of the film 8, which is stretched in the gate plane 46. The section 48 is then moved in the vertical direction 50 by means of the driven supply rollers 54 as soon as the front side 26 of the cell stack 4 reaches the gate plane 46 and thus the section 48. The section 48 is only moved a short distance, i.e. typically over a distance that is less than the height of the cell stack 4, i.e. the extension of the cell stack 4 in the vertical direction 50. As a result of the movement of the section 48, the separator ends 20 of the cell stack 4 protruding on the front side 26 are bent in the vertical direction 50 and are connected to one another.

[0054] Furthermore, in the exemplary embodiment, a conveyor line 58 of the film-wrapping unit 10 adjoins the entrance gate 44. The conveyor line 58 is designed to further convey the cell stack 4 along the conveying direction 42, at least once the cell stack 4 has been fed to the conveyor line 58 via the entrance gate 44, as shown in Fig. 4. Subsequently, the cell stack 4 is conveyed further by the conveyor line 58, with the film 8 being carried along by the cell stack 4, so that it wraps around the cell stack 4 in a U-shape. This situation can be seen in Fig. 5.

[0055] The conveyor line 58 has two conveyor belts 60 arranged one above the other, between which the cell stack 4 is then conveyed. The two conveyor belts 60 exert pressure on the cell stack 4, which acts on the cell stack 4 in the vertical direction 50 and counter to the vertical direction 50. This firmly adheres the film 8 to the surface of the cell stack 4.

[0056] The entrance gate 44 also has a slider 62 that is movable in the vertical direction 50, specifically along the gate plane 46. The slider 62 is moved as soon as the rear side 28 of the cell stack 4 has passed the gate plane 46, whereby the film 8 is placed by the slider 62 around the rear side 28 of the cell stack 4. As a result, the film 8 then forms a banderol with two banderol ends 64. The two banderol ends 64 are then connected to each other.

[0057] Since the film 8 in the exemplary embodiment is formed from a thermoplastic film, the connection is achieved by welding using a heating element 66. The corresponding heating element 66 is elongated in the transverse direction 52 and is formed, for example, by a heating wire. Furthermore, the heating element 66 is formed, as shown in Fig. 7, on a counter-bearing 68 for the slide 62, against which the slide 62 presses according to the method. As shown in Fig. 6.

[0058] Additionally, a further heating element 70 is formed, which is also elongated in the transverse direction 52. The two heating elements 66, 70 are arranged offset from one another in the conveying direction 42. Both heating elements are also formed on the counter bearing 68.

[0059] The first heating element 66 then welds the two aforementioned band ends 64 together. This typically also separates the film 8 from a film web extending between the two aforementioned supply rollers 54. As a result, the film web is separated into two partial webs. The aforementioned second heating element 70 then welds the two partial webs back together to form a single film web, thereby restoring the original state.

[0060] 2 Device

[0061] 4 cell stacks

[0062] 6 single sheets

[0063] 8 Slide

[0064] 10 foil unit

[0065] 12 grippers

[0066] 14 Anode material

[0067] 16 Cathode material

[0068] 18 Separator material

[0069] 20 separator ends

[0070] 22 Conductor foil

[0071] 24 arrester flags

[0072] 26 Front

[0073] 28 Back

[0074] 30 sensors

[0075] 32 gripping jaw

[0076] 34 bar

[0077] 36 gripping jaw

[0078] 38 Drive roller

[0079] 40 belts

[0080] 42 Conveying direction

[0081] 44 Entrance Gate

[0082] 46 Gate Level

[0083] Section 48

[0084] 50 vertical direction

[0085] 52 Transverse direction

[0086] 54 supply rollers

[0087] 56 deflection rollers

[0088] 58 Conveyor Street

[0089] 60 conveyor belt

[0090] 62 Slider banderole ends heating element counter bearing heating element

Claims

Patent claims 1 . Method for producing an accumulator which has at least one cell stack (4) formed by stacked individual sheets (6), wherein the cell stack (4) is wrapped with a film (8) by means of a device (2).

2. Method according to claim 1, wherein the cell stack (4) is wrapped with the film (8) in an intermediate step which is carried out after a method step in which the individual sheets (6) are stacked to form the cell stack (4) and before a method step in which the cell stack (4) is introduced into a cell housing.

3. Method according to claim 1 or 2, wherein the cell stack (6) is fed to a foil wrapping unit (10) of the device (2) for wrapping with the foil (8) and wherein a section (48) of the foil (8) is stretched in a gate plane (46) of an input gate (44).

4. The method according to claim 3, wherein the cell stack (4) is moved with a front side (26) of the cell stack (4) in front in a conveying direction (42) towards the section (48).

5. The method according to claim 4, wherein the section (48) is moved in the vertical direction (50) as soon as the front side (26) of the cell stack (4) reaches the section (48), so that projecting separator ends (20) of the cell stack (4) are bent in the vertical direction (50).

6. Method according to claim 4 or 5, wherein the section (48) is clamped at the entrance of a conveyor line (58) of the foiling unit (10) extending in the conveying direction (42), wherein the conveyor line (58) has two conveyor belts (60) arranged one above the other, wherein the cell stack (4) is guided into the conveyor line (58) and wherein the cell stack (4) is clamped between the two conveyor belts (60) and is conveyed in the conveying direction (42), whereby the film (8) is wrapped around the cell stack (4).

7. The method according to claim 6, wherein a slider (62) of the input gate (44) is moved in the vertical direction (50) as soon as a rear side (28) of the cell stack (4) opposite the front side (26) passes the gate plane (46), so that the film (8) is placed around the rear side (28) of the cell stack (4).

8. Method according to one of claims 1 to 7, wherein the film (8) forms a banderol with two banderol ends (64) after wrapping the cell stack (4) and wherein the two banderol ends (64) are welded together by means of a heating element (66).

9. Method according to one of claims 1 to 8, wherein the film (8) is separated from a film web so that the film web is separated into two partial webs, and wherein the two partial webs are welded together by means of a heating element (70).

10. Device (2) for producing an accumulator by means of a method according to one of the preceding claims.

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