Device and method for producing a composite film

Abstract

The present invention relates to a device for producing a composite film from a film stack, which device has a receiving region for the film stack and an inductor which is designed and arranged so as to induce a current in at least portions of the film stack which is arranged in the receiving region and to thereby heat at least portions of the film stack, the inductor comprising one or more conductors.

Description

[0001] Device and method for producing a film composite

[0002] The present invention relates to a device for producing a film composite from a film stack with a receiving area for the film stack, wherein the device comprises an inductor which is designed and arranged to induce a current at least in part into the film stack which is arranged in the receiving area and thereby to heat the film stack at least in part.

[0003] When laminating battery cells, in particular Li-ion battery cells, a volume of a foil stack or an electrode stack is heated, preferably completely and / or homogeneously, in one of the manufacturing process steps.

[0004] Foil stacks known from the prior art comprise foils coated with an anode or cathode material, in particular copper or aluminum foils, which are arranged alternately on top of one another with a separator in between, based on the coating. The foil thickness of the foils is typically less than 25 micrometers, and depending on the design, a battery cell comprises a foil stack with up to over one hundred foils. Due to the internal structure of the foil stack with horizontally arranged foils coated with an anode or cathode material, the specific thermal conductivity in the foil stack is highly anisotropic and in the vertical direction, i.e., perpendicular to the main foil plane, is much lower than in the lateral direction, i.e., in the main foil plane. Typical values ​​in the lateral direction of the foil stack are over 200 Wm -1 K -1, while the specific thermal conductivity in the vertical direction of the foil stack, i.e. perpendicular to it, is only about 3 Wrrr 1 K -1 However, due to the form factor of the foil stack, high thermal time constants also exist in the lateral direction, which can be in a similar range of values ​​or even higher than the time constants in the vertical direction.

[0005] According to the known prior art, a heat output 21, symbolized by thick arrows in Fig. 12, for heating the foil stack 1 is impressed via two heating stamps 20a and 20b, as can be seen from Fig. 12.

[0006] Due to the low thermal conductivity in the vertical direction, this process step is time-consuming and, due to the inhomogeneous temperature budget (temperature load as a function of time) across the thickness of the film stack, leads to undesirable parameter variations within the individual sub-cells of the film stack or stack. An obvious approach to reducing cycle times is to couple the required heat output into the conductive films magnetically via induction rather than thermally via heating stamps. To achieve a significant improvement in heating rate and homogeneity of temperature development during the heating process compared to the state of the art, the inductively excited heat input is preferably as homogeneous as possible throughout the entire volume of the film stack.

[0007] According to the current state of the art, common arrangements of induction loops do not provide satisfactory results with regard to the homogeneity of the heat input for the existing geometry of the foil stack.

[0008] Fig. 13 shows, as a sectional view in an xz plane defined by the coordinate system shown in Fig. 13, an arrangement of a foil stack 1 and an inductor 3 known from the prior art, illustrating how the inductor 3 encircles or surrounds the foil stack 1 in the lateral plane, i.e., in the xy plane defined by the coordinate system shown in Fig. 13. In this way, the heat input in the vertical direction of the foil stack can be largely homogenized.

[0009] An excitation current I flows in the inductor 3, the direction of the excitation current I being represented by the symbols with the cross and the dot in the circle in Fig. 13.

[0010] The excitation current I flows into the sheet plane for a symbol with the cross in the circle and the excitation current I flows out of the sheet plane for the symbol with the dot in the circle.

[0011] In Fig. 14, as a sectional view in an xy plane of the arrangement from Fig. 13, it is shown that the currents or eddy currents i impressed into the foils or foil stack 1 by the excitation current I flowing in the inductor 3 ws only flow at the edge of the foils or foil stack 1. Consequently, the applied heat output 21 is also limited to the edge of the foils or foil stack 1, and the lateral heat input thus becomes highly inhomogeneous.

[0012] Another approach known in the current state of the art for homogeneously heating workpieces with a similar form factor to a foil stack consists in vertically enclosing a workpiece as disclosed in US 2022 / 0193741 A1. However, in the case of a foil stack as the workpiece, heat can only be coupled into the foil stack to a limited extent at typical excitation current frequencies between 500 Hz and 20 kHz, since the field lines of an induced magnetic field run primarily along the main plane of the foil, as shown in Fig. 15 by the field lines of an induced magnetic field with the magnetic field strength H symbolized as arrows. When combining foils with a foil thickness typical of the prior art and an excitation current frequency between 500 Hz and 20 kHz, no significant currents are induced in the foils or in the foil stack in the arrangements disclosed in US 2022 / 0193741 A1.A disadvantage of the current state of the art is that no homogeneous heat distribution is achieved in the foil stack.

[0013] Against this background, the present invention is based on the object of providing an improved device compared to the device mentioned at the outset, in particular with regard to achieving a homogeneous heat distribution in a foil stack.

[0014] This object is achieved by the subject matter having the features of independent claim 1. Advantageous developments of the invention are the subject matter of the dependent claims.

[0015] Accordingly, the invention provides that the inductor comprises one or more conductors.

[0016] It is preferably provided that the conductors are designed to be energized in the same direction with an excitation current.

[0017] The conductor(s) can be formed as a conductor loop or conductor windings, or as conductor loops or conductor windings. The conductor(s) can be part of an inductor winding.

[0018] The foil stack may be a cell stack, an electrode stack and / or a stack and / or comprise foils and / or films or metallic and / or metallized foils.

[0019] The film composite is preferably a battery cell or a component of a battery cell. One or all of the films of the film stack and / or film composite are preferably electrically conductive and / or metallic, or consist of metal, or comprise a metal.

[0020] A film preferably has two film surfaces and film edges. The plane in which a film has the greatest extent is preferably the film's main plane. The two film surfaces of a film are preferably arranged parallel to the film's main plane. The film thickness is preferably the distance between the two film surfaces of a film.

[0021] The film stack preferably comprises a plurality of films stacked one on top of the other. The films are preferably stacked in the film stack such that the main planes of the films run parallel. The outer film surfaces of the outer films of the film stack are preferably the main surfaces of the film stack. A film stack therefore preferably has exactly two main surfaces. The other outer surfaces of the film stack are preferably the side surfaces of the film stack and are preferably formed by the film edges.

[0022] Preferably, it is provided that the inductor at least partially adjoins the receiving area, wherein the foil stack can be arranged in the receiving area such that the inductor at least partially adjoins one or all main surfaces of the foil stack.

[0023] The term “adjacent” preferably includes a direct adjacency of two elements, i.e. without an intermediate element between the adjacent elements, as well as an indirect adjacency, i.e. with one or more intermediate elements between the adjacent elements.

[0024] It is preferably provided that the inductor is arranged such that at least partially a conductor of the inductor or a part of the inductor adjoins a surface delimiting the receiving space and at least partially another conductor or another part of the inductor adjoins an opposite surface delimiting the receiving space and / or that the foil stack can be arranged in the receiving area such that at least partially a conductor or a part of the inductor adjoins a main surface of the foil stack and at least partially another conductor or another part of the inductor adjoins another main surface of the foil stack.

[0025] Preferably, it is provided that at least two conductors or parts of the inductor are arranged in a mirror image, directly above one another or with a maximum, in particular horizontal, offset of half, one third or one quarter of the distance between two, in particular straight, segments of a conductor.

[0026] Preferably, the inductor has straight segments, wherein the segments run parallel to a longitudinal or transverse side of the receiving space and / or the foil stack.

[0027] It is conceivable that laterally adjacent straight segments of the inductor are preferably flowed through by the excitation current in opposite directions.

[0028] In one embodiment, straight segments or the straight segments of the inductor are distributed laterally over the entire receiving area, resulting in a preferably uniform distribution of the straight segments along the main surfaces of the foil stack.

[0029] Preferably, the inductor and / or the conductor(s) comprise a solid conductor, a solid wire winding, a stranded wire winding, a round or rectangular tube, a multilayer conductor comprising metal foils and / or sheets, and / or a disc and / or round conductor winding, and / or the conductor(s) are designed to be single- or multi-winding and / or meandering. Preferably, the inductor and / or the conductor(s) comprise internal cooling.

[0030] Preferably, the device comprises a magnetically active layer.

[0031] It is preferably provided that the magnetically active layer comprises ferrite, an iron powder alloy, a laminated core and / or a nanocrystalline material and / or is designed in the form of a plate, in particular with grooves.

[0032] It is preferably provided that the inductor and / or the conductor(s) are arranged at least partially on or in the magnetically active layer.

[0033] The device is preferably designed in such a way that a homogeneous heat input into the film stack can take place and / or correspondingly high heating rates can be achieved both in the vertical direction of the film stack, i.e. in the stacking direction, and in the lateral direction of the film stack, i.e. in the lateral plane.

[0034] The device is preferably designed such that a distribution of impressed currents can be induced in a foil stack, which enables a homogenized heat input into the foil stack and thus can ensure high heating rates of the foil stack with only small internal temperature gradients in the foil stack.

[0035] The inductor is preferably flexibly adaptable to the dimensions of the foil stack, in particular so that the best possible compromise between lateral and vertical heat propagation can be achieved. The invention thus preferably solves a pressing problem for battery manufacturers. With the device and / or method according to the invention, the process of heating the foil stack during production can preferably be significantly accelerated, while simultaneously reducing the parameter variation within the foil stacks or the battery cells.

[0036] The invention also relates to a method for producing a film composite from a film stack, in particular using a device according to the invention, wherein a current is induced into the film stack at least in some areas by means of an inductor, whereby the film stack is heated at least in some areas in order to produce a film composite from the film stack.

[0037] The current in the foil stack or the current impressed into the foil stack is preferably an eddy current.

[0038] It should be noted here that the terms "a" and "an" do not necessarily refer to exactly one of the elements, although this represents a possible embodiment, but can also refer to a plurality of the elements. Likewise, the use of the plural also includes the presence of the element in question in the singular, and conversely, the singular also encompasses several of the elements in question. Furthermore, all features of the invention described herein can be combined with one another as desired or claimed in isolation from one another.

[0039] Further advantages, features, and effects of the present invention will become apparent from the following description of preferred embodiments with reference to the figures, in which identical or similar components are designated by the same reference numerals. Herein:

[0040] Fig. 1 to Fig. 4: each show sectional views of an embodiment of a device according to the invention.

[0041] Fig. 5: a representation of the orientation of an induced magnetic field perpendicular to a main foil plane. Fig. 6 and Fig. 7: each schematic representations of possible cross-sections of conductors of an embodiment of a device according to the invention.

[0042] Fig. 8 and Fig. 9: each show sectional views of an embodiment of a device according to the invention.

[0043] Fig. 10 and Fig. 11 : each show schematic representations of possible geometries of lines of an inductor of an embodiment of a device according to the invention.

[0044] Fig. 12 to Fig. 14: each show sectional views of embodiments of a device from the prior art.

[0045] Fig. 15: a representation of the orientation of an induced magnetic field along a foil main plane.

[0046] Fig. 1 shows part of an inductor 3 having a meandering conductor. The meandering conductor is arranged on a main surface of the foil stack 1. An excitation current I flows through the meandering conductor, the direction of which is indicated by the arrows in Fig. 1.

[0047] As can be seen from Fig. 2, a meandering conductor 3a and 3b is arranged above and below the foil stack 1. The symmetry shown in Fig. 2, in which the windings of the inductor or the meandering conductors 3a and 3b are arranged in a mirror image above (conductor 3a) and below (conductor 3b) the foil stack 1 and / or are traversed by the excitation current I in the same direction, provides the best possible results with regard to the vertical symmetry of the heat input. Arrangements are conceivable in which conductors 3a and 3b are each arranged in the form of a conductor loop above (conductor 3a) and below (conductor 3b) the foil stack 1, as can be seen from Figs. 3 and 4.

[0048] If the excitation current I flows through the conductors 3a and 3b in the same direction, the field lines of an induced magnetic field with the magnetic field strength H run vertically through the foil stack 1, as shown by the closed arrows in Fig. 3, and depending on the penetration depth and thickness of the foil stack, heat is introduced into the interior of the foil stack 1.

[0049] If the excitation current I does not flow through the conductors 3a and 3b in the same direction, the field lines of an induced magnetic field with the magnetic field strength H do not pass completely through the foil stack 1, as shown by the closed arrows in Fig. 4.

[0050] An opposite orientation of the excitation currents I in the conductors 3a and 3b leads, particularly in the center of the foil stack 1, to an orientation between the main foil plane and the field lines of an induced magnetic field with the magnetic field strength H as shown in Fig. 4. In such arrangements, the heat input is thus concentrated on the foils located on the outside of the foil stack 1. In US Pat. No. 5,397,877 A, such an arrangement is used for the homogeneous heating of flat metallic workpieces. Due to the resulting field line pattern, the arrangement shown in Fig. 4, or such a routing of the excitation current, is preferably unsuitable for the problem considered here.

[0051] In the lateral plane, the heat input in both arrangements shown in Figs. 3 and 4 is concentrated at the locations of the inductor 3 or the conductors 3a and 3b. For the inductive heating of the foil stack 1, approaches are preferably used which imprint field lines of an induced magnetic field perpendicular to the main foil plane, as shown in Fig. 5 by the field lines of an induced magnetic field with the magnetic field strength H symbolized as arrows.

[0052] The field lines of induced magnetic fields with the magnetic field strength H, represented in Fig. 2 by the closed arrows, correspond to the field lines shown in Fig. 3. This preferably leads to the best possible results with regard to the vertical symmetry of the heat input into the foil stack 1. In the lateral direction, the introduced heat output 21 continues to be concentrated in the area of ​​the conductors 3a and 3b. However, the meandering shape of the conductors 3a and 3b achieves a uniform distribution, so that any temperature gradients that arise in the foil stack 1 can equalize with a short time constant.

[0053] An offset between the two meandering conductors 3a and 3b above and below the foil stack 1 in the x-direction, which is defined by the coordinate system in Fig. 2, leads to an increasing decrease in the heat input into the foils in the region of the middle of the foil stack 1 up to the extreme case of an opposite current flow to the two meandering conductors 3a and 3b, in which a magnetic field is formed as shown in Fig. 4 and where, for the reason described above, less or no heat is introduced into the middle foils.

[0054] The meandering conductors 3a and 3b preferably lie directly above one another or are arranged with a maximum, in particular horizontal, offset equal to half, one-third, or one-quarter of the distance between two, in particular straight, segments of a meandering conductor 3a or 3b. The parts of the meandering conductors 3a and 3b that lie above one another or are arranged with a maximum offset are preferably traversed by excitation current I in the same direction. Preferably, the meandering conductors 3a and 3b are not offset from one another. By appropriately selecting the number of loops and / or the spacing of the, in particular straight, segments of the loops of the meandering conductors 3a and 3b and / or the frequency of the excitation current I, the device can preferably be individually adapted to the geometry of a foil stack 1.

[0055] As a result of the currents impressed into the foil stack 1, the coupled magnetic field is increasingly shielded into the interior of the foil stack 1. As a result, the heat input is greatest in the outer foils of the foil stack 1 and decreases continuously towards the middle of the foil stack 1. This effect can be counteracted by using a low frequency excitation current due to the resulting greater penetration depth. In the lateral direction, the highest possible number of loops of the meandering conductors 3a and 3b results in a tighter distribution of the heat input and thus a laterally more homogeneous temperature distribution during heating. However, this is only possible if there are no edge effects at the ends of the meandering conductors 3a and 3b in the x-direction, which is defined by the coordinate system in Fig. 2, which can be circumvented by a sufficiently high frequency of the excitation current.

[0056] The straight segments of the lines 3a and 3b can run along the transverse side of the foil stack 1 as shown in Fig. 1, but alternatively also along its longitudinal side.

[0057] As an alternative to a single inductor with two meandering conductors, the described effect can also be achieved with similar geometries, such as with several conductors arranged in parallel. A magnetic field, as shown in Fig. 2 or Fig. 3, is particularly preferably generated, particularly by appropriately orienting the excitation current.

[0058] The inductor and / or the conductor(s) can be designed in the form of a solid conductor. The solid conductor is, as is usual in the field of inductive heating, preferably designed as a round tube 7 or a rectangular tube 8, the cross-sections of which can be seen in Figs. 6 and 7. The round tube 7 and / or the rectangular tube 8 preferably comprise copper and / or are provided with an internal cooling system 9, e.g. with water and / or compressed air cooling, as can be seen in Figs. 6 and 7. The inductor and / or the conductor(s) can also be designed in the form of a foil, sheet metal, solid wire and / or stranded wire winding. This preferably has no significant effect on the impression of the magnetic field.

[0059] The properties of the device can be further improved through the targeted use of magnetically active layers with permeable materials, such as ferrites or laminated cores, but also iron powder alloys or nanocrystalline materials. Preferably, the conductors 3a and 3b can be backed with a magnetically active layer, e.g., with plates 4a and 4b comprising a magnetically active material with a permeability p, as shown in Fig. 8. As a result, for a given excitation current in the region of the foil stack 1, the magnetic field strengths are increased, thereby increasing the heat input into the foil stack 1. This allows the excitation currents required for heating to be reduced. At the same time, the rear space of the inductor is shielded from the magnetic fields, so that currents or eddy currents coupled into the periphery cannot lead to asymmetries in the heat input into the foil stack 1.

[0060] Particularly preferably, the inductor and / or the respective conductors 3a and 3b are at least partially embedded in the magnetically active layer, for example in the form of plates with grooves 5a and 5b, as shown in Fig. 9. The embedding is preferably designed such that the meandering conductors 3a and 3b are embedded flush with the magnetically active layer. Preferably, the inductor and magnetically active layer form a flat surface. The coupled magnetic fields are thereby preferably more strongly directed. This preferably counteracts the above-mentioned edge effects at the ends of the meandering conductors 3a and 3b, so that the meandering conductors 3a and 3b can be realized with more loops while maintaining a constant excitation current frequency in order to achieve a more densely meshed heat input laterally.It is also conceivable to reduce the frequency of the excitation current while maintaining the same inductor geometry to further homogenize the vertical symmetry of the heat input. The power consumption of the device is preferably reduced even further in an arrangement such as that shown in Fig. 9 compared to the use of simple ferrite plates, as shown in Fig. 8.

[0061] Fig. 10 shows an inductor with two meandering conductors 3a and 3b, where the conductors 3a and 3b are connected via a connection 3c. The meandering conductor 3a is arranged above the foil stack 1, and the meandering conductor 3b is arranged below the foil stack. The conductors 3a and 3b are arranged mirror-inverted, so that the straight and curved segments of the meandering conductors 3a and 3b lie one above the other. Due to the flow direction of the excitation current I indicated by the arrows in Fig. 10, the meandering conductors 3a and 3b are energized in the same direction.

[0062] Fig. 11 shows an inductor with two meandering conductors 3a and 3b, wherein the meandering conductors 3a and 3b are connected via a connection 3c. The meandering conductor 3a is arranged above the foil stack 1, and the meandering conductor 3b is arranged below the foil stack. The meandering conductors 3a and 3b are arranged one above the other in such a way that the straight segments of the meandering conductors 3a and 3b lie one above the other and the curved segments of the meandering conductors 3a and 3b do not lie one above the other. Due to the flow direction of the excitation current I indicated by the arrows in Fig. 11, the meandering conductors 3a and 3b are energized in the same direction.

[0063] The inductors shown in Fig. 10 and Fig. 11 differ only slightly in their effect. Relevant aspects are, in particular, the geometric requirements for integrating the device into a system.

Claims

Patent claims 1. Device for producing a film composite from a film stack with a receiving area for the film stack, wherein the device comprises an inductor which is designed and arranged to induce a current at least in part into the film stack arranged in the receiving area and thereby to heat the film stack at least in part, characterized in that the inductor comprises one or more conductors.

2. Device according to claim 1, characterized in that the inductor at least partially adjoins the receiving area, wherein the foil stack can be arranged in the receiving area such that the inductor at least partially adjoins one or all main surfaces of the foil stack.

3. Device according to claim 1 or 2, characterized in that the inductor is arranged in such a way that at least partially a conductor of the inductor or a part of the inductor adjoins a surface delimiting the receiving space and at least partially another conductor or another part of the inductor adjoins an opposite surface delimiting the receiving space. surface and / or that the foil stack can be arranged in the receiving area in such a way that at least partially a conductor or a part of the inductor adjoins a main surface of the foil stack and at least partially another conductor or another part of the inductor adjoins another main surface of the foil stack.

4. Device according to one of the preceding claims, characterized in that at least two conductors or parts of the inductor are arranged in mirror image, directly above one another or with a maximum, in particular horizontal, offset of half, one third or one quarter of the distance between two, in particular straight, segments of a conductor.

5. Device according to one of the preceding claims, characterized in that the inductor has straight segments, wherein the segments run parallel to a longitudinal or transverse side of the receiving space and / or the foil stack.

6. Device according to one of the preceding claims, characterized in that the inductor has straight segments, whereby laterally adjacent straight segments of the inductor are traversed by the excitation current in opposite directions.

7. Device according to one of the preceding claims, characterized in that the inductor has straight segments which are distributed laterally over the entire receiving area, so that a uniform or substantially uniform distribution of the straight segments along the main surfaces of the foil stack results.

8. Device according to one of the preceding claims, characterized in that the inductor and / or the conductor(s) comprise a solid conductor, a solid wire winding, a stranded wire winding, a round or rectangular tube, a multi-layer conductor comprising metal foils and / or sheets, and / or a disc and / or round conductor winding and / or that the conductor(s) are single- or multi-winding and / or meandering.

9. Device according to one of the preceding claims, characterized in that the inductor and / or the conductor(s) comprise internal cooling.

10. Device according to one of the preceding claims, characterized in that the device comprises a magnetically active layer.

11. Device according to claim 10, characterized in that the magnetically active layer comprises ferrite, an iron powder alloy, a laminated core and / or a nanocrystalline material and / or is designed in the form of a plate, in particular with grooves.

12. Device according to one of claims 10 or 11, characterized in that the inductor and / or the conductor(s) are arranged at least partially on or in the magnetically active layer.

13. A method for producing a film composite from a film stack, in particular using a device according to one of the preceding claims, characterized in that a current is induced into the film stack at least in some areas by means of an inductor, whereby the film stack is heated at least in some areas in order to produce a film composite from the film stack.

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