Method for inspecting a battery cell stack with respect to the position of a battery cell layer

Abstract

To provide a testing method for a battery cell layer laminate.SOLUTION: A testing method for a battery cell layer laminate includes: obtaining a geometrical shape of at least one large area part of a large area part of at least an anode 2a and / or a cathode 2b; laminating battery cell layers on a laminate 1; irradiating the laminate with X-ray for location testing of the anode and / or the cathode to obtain a maximum inter-edge distance present between edges of an electrode of a type considered with respect to at least one pair of opposing side surfaces of the laminate by using detected X-ray; testing whether or not the distance is smaller than a first permissible error value; defining as an overhang amount a half of a value for which the distance is smaller than a first permissible error value when a result is positive; obtaining the distance from a sum of shortest dimensions related to all calculation directions of the electrode of the type considered on the one hand, and on the other hand, testing whether or not it is smaller than value obtained from difference between a second permissible error value and a half of the overhung amount; and evaluating that the laminate is permissible when the result is positive.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for inspecting stacks of multiple battery cell layers in the form of anodes, cathodes, and separators, sometimes referred to as electrode separator composites (ESVs), which may be provided as components of batteries, among other things.

[0002] In automated battery production, battery cell layers are stacked into a stack using a laminator (see U.S. Patent Application Publication No. 2022 / 0216501), where the stacking accuracy of the battery cell layers, especially the electrodes, is a quality criterion for the laminator's throughput. All edges of polygonal, especially rectangular, battery cell layers must have a defined spacing distance from one another and within a defined tolerance range, on the one hand to ensure the best possible electrochemical performance of the battery, and on the other hand to avoid short circuits between adjacent electrodes due to insufficient stacking accuracy. Such short circuits could lead to the failure of the battery in question.

[0003] Considering the lamination accuracy of currently used lamination machines, to reliably avoid short circuits between adjacent electrodes due to insufficient lamination accuracy, it may be envisioned that the separator of the stack is dimensioned larger than the anode, and the anode is dimensioned larger than the cathode, so that there is an overhang of, for example, 1 millimeter between the separator and anode on the one hand, and between the anode and cathode on the other hand, all around. Such overhang also prevents a decrease in the chemical performance of the stack due to inaccurate electrode positioning. However, oversizing of the anode and separator due to such tolerances increases material consumption in the production of the stack, thereby increasing the cost, space required, and weight of the stack, and ultimately the weight of the battery. Therefore, it may be useful to minimize oversizing of battery cell layers in the stack due to such tolerances. To this end, in order to avoid short circuits between adjacent electrodes due to insufficient lamination accuracy, the lamination accuracy of the lamination machine used for lamination should be improved and / or quality assurance should be improved within the production of the stack, so that the production of short-circuited stacks can be sufficiently reliably avoided or reliably sorted out within the production.

[0004] WO 2016 / 114257 discloses a method for inspecting ESVs using X-rays.

[0005] The problem on which the present invention is based is to provide a method for determining the stacking accuracy of battery cell layers of a battery cell stack, which can be carried out as simply and / or quickly as possible with sufficient accuracy.

[0006] This problem is solved in a method according to claim 1. Preferred embodiments of the method according to the invention are the subject of further claims and will become apparent from the following description of the invention.

[0007] According to the present invention, there is provided a method for testing at least one stack of a plurality of battery cell layers in the form of an anode as a first type of electrode, a cathode as a second type of electrode, and a separator (which separates and electrically insulates the anode and cathode), wherein the battery cell layers have polygonal, preferably rectangular, large area portions. The large area portions of the battery cell layers can have at least partially different sizes. The battery cell layers are stacked in a stacking direction aligned perpendicular to the large area portions. The electrodes of the battery cells can differ at least with respect to the active material they contain, whereby an electrode designated as an anode is anodic active and an electrode designated as a cathode is cathodic active (respectively with respect to the discharge of the battery cell).

[0008] The battery cell layer may preferably be designed plate-like. By "plate-like" is understood here a body or body section having two (outer) large-area portions extending in the longitudinal and transverse directions of the body (for example, in the case of a serpentine course of a strip-shaped separator, the section lying between adjacent electrodes here represents a plate-shaped separator), in which the (maximum) height of the body, corresponding to the (maximum) spacing distance of the large-area portions, is smaller (in particular by a factor of at most 1 / 10, 1 / 100, or 1 / 100) than the (maximum) length and the (maximum) width.

[0009] In a first calculation step of the method, the geometry (i.e., geometric data, in particular regarding the shape and dimensions) of at least one large-area portion of at least (all) anodes and / or (all) cathodes, and possibly additionally of the large-area portions of the separator, is determined, preferably in an individualized state of the battery cell layers.

[0010] The calculation of the geometry of at least the anode and / or cathode can be preferably performed based on images from an optical camera system, i.e., by a visible light imaging system including one or more cameras. This allows for a simple and cost-effective implementation of the first calculation step. Here, the image capture of the camera of the camera system can be preferably recorded in a top view, i.e., with a "line of sight" to large areas of the battery cell layer, particularly preferably with the optical axis of the camera of the camera system vertically aligned with these large areas. This can also be advantageous for the implementation of the first calculation step, since it allows for the capture of as large an area of ​​the battery cell as possible.

[0011] In the stacking step, the battery cell layers are stacked in the stack. Here, it may be assumed that the battery cell layers are stacked in the stack in a defined order and / or that the order in which this is done is determined and stored. These first calculation step and stacking step can preferably be performed at least partly simultaneously, for example by determining the geometry of the upper large area from the battery cell layer placed on the formed stack or from the battery cell layer to be placed next. However, it may be assumed that the stacking step is performed only in connection with the first calculation step.

[0012] Subsequently, for a position check of at least the anode and / or the cathode, insofar as these have been geometrically measured in the first calculation step, a number of method steps are carried out, where, if a position check is carried out for the anode and the cathode, these method steps are carried out separately (but preferably at least temporarily simultaneously) for the anode on the one hand and the cathode on the other hand, respectively.

[0013] In the second calculation step, the stack is first irradiated with X-rays emitted by an X-ray irradiator and detected by an X-ray detector, where the X-rays (i.e., at least one beam, particularly its central beam) are aligned vertically with respect to a large area of ​​the battery cell layer. Preferably, relative movement between the stack and the X-rays is generated by moving the stack while the X-ray irradiator and the X-ray detector are stationary. This relative movement may preferably be linear. The detected X-rays are then used to determine the maximum edge separation distance between the edges of at least one pair of opposing side surfaces of the stack. According to the present invention, this separation distance is essentially determined along the most direct or shortest possible path.

[0014] In a first inspection step, it is then checked whether this maximum edge spacing is less than a first tolerance value. If not, i.e., if the maximum edge spacing is not less than the first tolerance value and is therefore equal to or greater than the first tolerance value, the laminate is evaluated as unacceptable. On the other hand, if the maximum edge spacing is less than the first tolerance value, a second inspection step is further performed.

[0015] In this second test step, it is checked whether the determined maximum edge spacing is smaller than a value determined from the sum of the shortest (geometric) dimensions of all electrodes (anodes or cathodes) in the calculation direction (the direction of connection between the pairs of opposite side surfaces of the stack), on the one hand, and from the difference between a second tolerance value and half the overhang, on the other hand. The overhang is defined here as half the value by which the maximum edge spacing is smaller than the first tolerance value. If this second test step produces a negative result, i.e., if the maximum edge spacing is not small and is therefore equal to or greater than the value determined from the sum of the shortest dimensions of all electrodes, on the one hand, and from the difference between the second tolerance value and half the overhang, on the other hand, the stack is evaluated as unacceptable. On the other hand, if the second test step yields a positive test result, i.e., the maximum edge separation distance is smaller than the value determined from the sum of the shortest extensions of all electrodes on the one hand and the difference between the second tolerance value and half the overhang on the other hand, the stack is evaluated as acceptable. A stack evaluated as acceptable may be expected to be used without restriction for the manufacture of batteries.

[0016] The method according to the present invention preferably combines the geometric data from the first calculation step with the calculation results from the second calculation step, whereby the positions of all anodes and / or cathodes can be inspected by specific evaluation in multiple inspection steps. This is possible despite the relatively easy-to-maintain type of (perpendicular) irradiation of the stack with X-rays during the second calculation step. This type of irradiation, in particular, can lead to an inability to accurately determine the edges of all of these electrodes by evaluation of the X-rays measured by the X-ray detector. Rather, even though only the separation distance between the most widely separated edges of each electrode forming a selected pair of sides of the stack is determined, the combination of all geometric data of each electrode (anode and / or cathode) and specific evaluation in multiple inspection steps ensures with a relatively high degree of accuracy that all of the considered electrodes have sufficient positional accuracy. This allows for a relatively rapid inspection of the stack, since the perpendicular irradiation allows the X-rays to move through the stack in a fast and easy manner.

[0017] According to a preferred embodiment of the method according to the invention, it may be assumed that in the first calculation step, the contours of the edges or edge sections forming all corners of each electrode, i.e., anode or cathode, are determined. This would result in the complete geometric shape of a large area of ​​each of these electrodes. This makes it possible to achieve sufficiently accurate test results for the entire stack, even if the first calculation step is performed only for some battery cell layers, for example, exclusively for the cathode and / or anode. However, it may be sufficient in principle to determine the contours of the edges or edge sections forming only some corners of each electrode in the first calculation step.

[0018] To achieve the most reliable inspection results for the stack, it is preferable to perform the second calculation step and the subsequent inspection step for at least two or exactly two pairs of opposing sides of the stack. Therefore, in connection with a preferred design of battery cell layers with a rectangular large area, calculation and inspection are performed for each combination of edges that defines the maximum separation distance for the length of each electrode, on the one hand, and the maximum separation distance for the width of each electrode, on the other hand. This allows for particularly precise inspection of the relative positions of the battery cell layers, which can be achieved with just two simple linear relative movements between the stack and the X-ray. The second calculation step and the first and second inspection steps can be performed sequentially for at least two or exactly two pairs, so that the stack is, for example, first moved relative to the X-ray along the longitudinal direction of the stack, and then, after rotating by, for example, 90° around the stacking direction, moved relative to the X-ray along the width direction. However, simultaneous capture of two pairs of edges can also be performed.

[0019] According to a preferred embodiment of the method according to the invention, it may be assumed that only one type of electrode, in particular only the cathode, is inspected according to the second calculation step and the first and second inspection steps, since for this type of electrode based on a specifically structured structure, it may not be possible to accurately or unambiguously determine the position of all edges on the basis of an image that can be determined by evaluation of the X-rays detected by the X-ray detector, which may be due to their relatively significant absorption properties for X-rays.

[0020] In contrast, simpler and / or more accurate types of evaluation may be envisioned for the relative positions of other types of electrodes, particularly anodes. To this end, in a further calculation and inspection step of the method according to the present invention, which may optionally be performed as part of or simultaneously with the second calculation step, the stack is irradiated with X-rays irradiated by an X-ray irradiator and detected by an X-ray detector, the X-rays being aligned perpendicularly to a large area of ​​the battery cell layers. The X-rays detected for at least one side of the stack are used to determine the maximum edge spacing between the edges of all electrodes of this type assigned to this side of the stack, and based on this, it is checked whether this edge spacing is smaller than the third tolerance value. If a negative result is obtained, i.e., if the maximum edge spacing is not smaller but is greater than or equal to the third tolerance value, the stack is evaluated as unacceptable or rejectable. A rejected stack can be considered, in particular, to be definitively unsuitable for further use in the manufacture of batteries. In contrast, if a positive result is obtained, the stack is evaluated as acceptable. Preferably, in order to achieve the most accurate inspection results possible, further calculation and inspection steps are performed on all sides of the stack, but at least on the sides of the stack that define at least two of the edges of the stack extending in the stack direction.

[0021] The procedure for the second calculation step and the first and second inspection steps is based on a simplification of the calculation results. This simplification is based on the assumption that, for evaluation purposes, the smallest of all electrodes, in terms of the edge-to-edge dimension of a pair, represents one of the edges that determines the maximum edge-to-edge distance of this pair. The smallest electrode is determined in the context of the first calculation step. This can lead to an evaluation of the stack as unacceptable, which is not actually given, because the smallest electrode does not necessarily represent one of the edges that defines the maximum edge-to-edge distance. Therefore, the simplification is selected so that a certain degree of inaccuracy exists only in the evaluation of the stack as unacceptable.

[0022] It may therefore be expedient to re-examine stacks that have been assessed as unacceptable, in particular in the second calculation step and the first and second inspection steps, and possibly also in further calculation and inspection steps. For this purpose, it may be expedient to provide that if a stack has been assessed as unacceptable, the stack is additionally inspected in a third inspection step with respect to maintaining at least one tolerance range, in which case the stack is assessed as rejected in the negative and the stack is assessed as acceptable in the positive.

[0023] In a third inspection step, the stack can be preferably irradiated with X-rays irradiated by an X-ray irradiator and detected by an X-ray detector, where the orientation of the stack relative to the X-rays is selected so that at least one edge of the stack extending along the stacking direction is completely captured at least at two different positions in the space covered by the X-rays, and based on this, the relative positions of the corners of the battery cell layers forming said edge of the stack (or the edge sections defining these corners) can be determined. This procedure can be similar to or correspond to the procedure in conventional computed tomography.

[0024] According to a preferred embodiment of the method according to the invention, it may be assumed that the battery cell layers are inspected for the presence of buckles during or after the stacking step, since such buckles could falsify the results of the stack inspection. Buckles here are understood to mean angled sections of large areas of the battery cell layers, in particular sections angled at least 45° or at least 90°. The angle of this section can also be approximately 0° / 360°, so that two sections of the battery cell layer run essentially parallel. Such a buckle inspection can also be performed simultaneously with the first calculation step, and can even be integrated into the first calculation step, in particular by using the same device (in particular an optical camera system).

[0025] Buckle testing may suitably be performed by determining and evaluating the geometry of the battery cell layers and / or by determining and evaluating the geometry of the stack.

[0026] Within the scope of buckle inspection, determining the geometry of the battery cell layers and / or determining the geometry of the stack can also preferably be performed using an optical camera system. Here, the images of the camera system can preferably be recorded in a top view of a large area of ​​the battery cell layers. Such an arrangement of the camera system with respect to the battery cell layers can be envisaged, in particular, when the geometry of the individual battery cell layers is to be determined after or during placement in the stack to be formed. Alternatively, it can be envisaged that, in order to determine the geometry of the battery cell layers in the formed stack, the images of the camera system are recorded in a side view of the stack.

[0027] Determining the geometry of the stack may in particular involve determining the height of the stack along the stacking direction at multiple points, i.e., the extension of the stack, which may also be done mechanically in a relatively simple and cost-effective manner.

[0028] The battery cells used within the scope of the method according to the present invention can preferably be designed so that the large area of ​​the anode is larger than the large area of ​​the cathode and / or the large area of ​​the separator is larger than the large area of ​​the cathode and preferably also larger than the large area of ​​the anode. Designing the large area of ​​the different battery cell layers to different sizes should result in a relatively large overall overhang of each of the battery cell layers (separator and anode) compared to the next smaller battery cell layer. This makes it possible, in particular, to perform the second calculation step and any further calculation and inspection steps more efficiently. This can be due to different absorption rates of the different battery cell layers for X-rays. These different absorption rates can be due to differences in the materials from which the different battery cell layers are designed. Here, the cathode may have the highest absorption rate and the separator the lowest.

[0029] In the following, the invention will be explained in more detail on the basis of the designs and examples shown in the drawings, which are each shown in a schematic diagram. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view of a section of a stack of battery cell layers in the form of an anode, cathode, and separator. [Figure 2] FIG. 1 shows stacking areas for the cathode, anode, and separator of the stack. [Figure 3] 1 shows an individualized battery cell layer of a stack according to a first variant and a camera system for use in the first calculation step of the method according to the invention; FIG. [Figure 4] 1 shows an individualized battery cell layer of a stack according to a second variant and a camera system for use in the first calculation step of the method according to the invention; [Figure 5] 1 shows a stack and a camera system according to a first variant for use in the buckle inspection of the method according to the invention; FIG. [Figure 6] 4 shows a stack and a camera system according to a second variant for use in the buckle inspection of the method according to the invention; FIG. [Figure 7] 1 is a side view of a laminate and a mechanical measurement system for use in buckle inspection in a method according to the invention; FIG. [Figure 8] FIG. 8 is a top view of the stack and measurement system according to FIG. 7. [Figure 9] FIG. 2 shows a stack and an X-ray system for use in the second calculation step of the method according to the invention. [Figure 10] FIG. 1 shows one position of the stack relative to an X-ray detector of an X-ray system. [Figure 11] FIG. 1 shows one position of the stack relative to an X-ray detector of an X-ray system. [Figure 12] FIG. 1 shows one position of the stack relative to an X-ray detector of an X-ray system. [Figure 13] FIG. 1 shows one position of the stack relative to an X-ray detector of an X-ray system. [Figure 14] FIG. 1 shows one position of the stack relative to an X-ray detector of an X-ray system. [Figure 15] FIG. 10 is a diagram showing dimensions of the stack relative to the cathode. [Figure 16] FIG. 10 shows a stack and an X-ray system for use in the third inspection step of the method according to the invention. [Figure 17] FIG. 17 shows an image of a section of a stack made using the X-ray system according to FIG. 16.

[0031] In the context of battery cell production, a stack 1 can be produced that includes battery cell layers in the form of plate-like electrodes 2 and electrically insulating plate-like separators 3, arranged in alternating order along a stacking direction 4. These electrodes 2 are again arranged in the stack 1 in a design and arrangement that corresponds to their use as anodes 2a and cathodes 2b, alternatingly. The electrodes 2 and separators 3 have rectangular major areas, with the anodes 2a, cathodes 2b, and separator 3 major areas being of different sizes in order to avoid short circuits between adjacent anodes 2a and cathodes 2b and excessive losses in the electrical performance of the battery to be produced, despite imprecisions in the stacking that are still within corresponding tolerances, at least. According to FIG. 1, it can be assumed that the cathode 2b has the smallest large area and the separator 3 has the largest large area, which results in an overhang of the anode 2a with respect to the cathode 2b on the one hand and an overhang of the separator 3 with respect to the anode 2a (and therefore also to the cathode 2b) on the other hand on the edge side over the entire range (i.e. both with respect to the width and the length of the battery cell layers).

[0032] The plate-like separators 3 may at least partially be sections of a serpentine-guided separator strip (not shown). The overhanging edge regions of adjacent separators 3 may be glued together.

[0033] 2 shows possible configuration specifications for sufficiently accurate stacking of battery cell layers for one of all four edges of the stack 1 extending along the stacking direction 4, in which case these configuration specifications would have to be met for all of these edges. Thus, for each of the anode 2 a, cathode 2 b, and separator 3, one stacking area A within which the edges of these different types of battery cell layers should reside is provided. A ,A K ,A S In addition, for each of the various types of battery cell layers, the optimum position S A ,S K ,SS are shown, and in this case, these optimal positions S A ,S K ,S S are the thicknesses of each layer in each stacking area A A ,A K ,A S These lamination areas A extend to the center of the interior. A ,A K ,A S For example, the width of each optimal position S A ,S K ,S S The difference between the stacked area A and the stacked area B can be 1.0 mm or ±0.5 mm on either side of the stacked area A for different types of battery cell layers of all the battery cells in the stacked body 1. A ,A K ,A S In addition to this, various lamination areas A A ,A K ,A S The minimum spacing distance d between AK ,d AS The anode 2a stacking region A may be provided. A and cathode 2b stacking area A K The minimum spacing distance d between AK , and the lamination region A for the anode 2a A and separator 3 for stacking area A S The minimum spacing distance d between AS and can be, for example, 0.8 mm each. This allows these two minimum spacing distances d AK ,d AS , and the anode 2a stacked tube region A A The cathode 2b stacking region A is formed through a linking portion having a width of K and separator 3 for stacking area A S There is also a minimum spacing distance between

[0034] The method according to the invention allows the simplest and fastest possible testing of the stack 1 with regard to a sufficiently accurate position of at least the electrodes 2 of the stack 1 by combining several calculation and testing steps.

[0035] In a first calculation step of the method, the geometry of each one of the large-area portions of all battery cell layers is determined. This is done using an optical camera system in a top view (see FIGS. 3 and 4), with the help of which at least one image of each individual battery cell layer is recorded and evaluated. Preferably, a first light source (not shown) is arranged on the same side of the individual battery cell layer as the at least one camera 5 of the camera system, and a second light source (not shown) may be arranged on the opposite side of the individual battery cell layer.

[0036] If the capture area 5a of the at least one camera 5 used is sufficiently large, the individualized battery cell layer can be completely captured without any relative movement with respect to this camera 5. However, to achieve a relatively high resolution, it may be envisaged to move the individualized battery cell layer and the at least one camera 5 relative to each other, in which case only a section of the battery cell layer is captured by each of the at least one camera 5. A relatively high resolution without relative movement can be achieved when using multiple cameras 5, which may each further have a capture area 5a smaller than the major surface area of ​​the battery cell layer. Figure 4 shows an example in this regard, in which one camera 5 is assigned to each of the four corners of the individualized battery cell layer.

[0037] Preferably, simultaneously with or after determining the geometry of the individualized battery cell layers in the first calculation step, the battery cell layers are stacked in the stack 1 in a defined number, and optionally in a later-ordered order, in the stacking step of the method.

[0038] During or after the stacking of the battery cell layers, these battery cell layers are further inspected for the presence of buckles. This can also be done using a camera system. This can preferably be the same camera system as used in the first calculation step, but it can also be a different camera system. Different camera systems can be used advantageously, for example, in the context of a series of inspections of multiple stacks, where these stacks simultaneously undergo different calculation and inspection steps that are carried out sequentially on each individual stack.

[0039] Figures 5 to 8 show various means for carrying out buckle inspection. For buckle inspection according to Figures 5 and 6, one camera system is used in each case.

[0040] In the camera system according to Fig. 5, the camera 5 is positioned in a top view of the large-area portion of the battery cell layer for image recording. This allows the camera to determine the geometry of the large-area portion of the battery cell layer of the (formed) stack 1 in a manner comparable to the procedure according to the first calculation step, and to check for the presence of buckles (not shown). This can preferably be performed with the geometric data for each battery cell layer previously determined in the first calculation step. However, this is not necessarily required, since buckles in the battery cell layers usually lead to geometric deviations of such magnitude that a buckle check may be sufficient based on a comparison of the determined geometry with a reference geometry defined for all battery cell layer types. Since the geometry of all battery cell layers of the stack 1 cannot be completely captured when recording images in a top view, it is envisaged that the buckling inspection will be carried out sequentially for each individual battery cell layer during stacking using a camera system according to FIG. 5, i.e. for each battery cell layer that is placed on the stack 1 formed during stacking, at least one image will be captured using camera 5 before a further battery cell layer is placed on the stack 1.

[0041] In contrast, in the camera system according to FIG. 6, the camera 5 is arranged to record images in a side view of the stack 1. This allows the progression of all battery cell layers to be determined simultaneously in the corresponding side view and the presence of buckles (not shown) to be checked. For as complete a buckle check as possible, images of at least two opposite sides of the stack 1 should be generated and evaluated, and for this purpose the camera system can include at least two cameras 5 (not shown). Alternatively, however, a relative rotation between the stack 1 and the camera system can be provided so that multiple sides of the stack are captured successively by images from the individual cameras 5. Since the camera system according to FIG. 6 allows all battery cell layers to be checked simultaneously for the presence of buckles, the corresponding buckle check can preferably be carried out on an already fully formed stack 1.

[0042] The buckle inspection according to Figures 7 and 8 is based on determining the respective height of the stack 1 at a number of measurement points. This can be done mechanically, for example, using a measurement probe 6. Preferably, at least one measurement point is assigned to each edge of the stack 1 extending along the stacking direction 4 or is located near this edge, since in particular the corners of the battery cell layers forming these edges are exposed to the risk of buckling during stacking.

[0043] Following the lamination step with buckle inspection, a second calculation step is performed, in which the stack 1 is irradiated with X-rays 9 irradiated by an X-ray irradiator 7 and detected by an X-ray detector 8 (see FIG. 9 ). Here, it is assumed that the X-rays 9 are aligned vertically with respect to a large area of ​​the battery cell layers, where the vertical alignment relates to a central beam 9 a of the X-rays 9 propagating from the X-ray irradiator 7 in a tapered or conical manner.

[0044] By evaluation of the X-rays detected with the X-ray detector 8, the positions of at least the edges of the anode 2a and the cathode 2b are determined, if possible.

[0045] Since the anode 2a is, on the one hand, larger than the cathode 2b and, on the other hand, only moderately absorbs X-rays, it is possible to determine the position of all edges of the anode 2a from the X-rays captured by the X-ray detector 8, since there is sufficient contrast for these edges in the corresponding image. The very slight absorption of X-rays by the separator 3, which has a larger surface area than the anode 2a, does not significantly impede this evaluation.

[0046] For the positional inspection of the anodes 2a, the determined positions of the edges of the anodes 2a in the further calculation and inspection steps of the method are calculated to determine the maximum distance d between the edges of all the anodes 2a forming the individual sides of the stack 1. max (See Figure 9) is obtained, and the maximum spacing distance d max is checked whether it is smaller than a respective (third) tolerance value, which may be different for different aspects of the stack 1. If each of these preconditions is met, the stack 1 is evaluated as acceptable; otherwise, the stack 1 is evaluated as unacceptable or rejected.

[0047] For the cathodes 2b, a position check like that provided for the anode 2a is not necessarily possible, since the position of the edges covered by the other cathodes 2b cannot be recognized or cannot be uniquely recognized due to the relatively strong absorption of X-rays by the cathodes 2b. This applies in particular to the edges of one of the cathodes 2b that are overlapped by all the other cathodes 2b in the arrangement with the X-ray irradiator 7. Therefore, in the second calculation step, the method assumes that the maximum edge separation distance (K_W_R_TD) existing between all edges of each pair of cathodes 2b is determined from the X-rays detected for two pairs of opposite sides of the stack 1. This is specifically shown in FIG. 15. If the anode 2a is designed in such a way that the position check described for this purpose cannot be performed, the method described for the cathode 2b can also be advantageously applied to the anode 2a.

[0048] For the sake of simplicity, only three cathodes 2b of the stack 1 are shown in FIG. 15 . The first cathode 2b′ has the largest dimension (length or width) in relation to the extension of the stack 1 between a specific pair of sides. Here, this first cathode 2b′ can be larger in this dimension than the second cathode 2b″, which can correspond to the defined nominal dimension associated with it. In contrast, the third cathode 2b′″ is the smallest (of all cathodes 2b of the stack) in relation to the considered dimension. Due to the at least partial coverage of the edges of the second and third cathodes 2b″ and 2b′″ by the first cathode 2b′ for X-rays, an unambiguous calculation of these covered edges may be hindered. For this reason, the second calculation step and the subsequent first and second inspection steps are based on a simplification of the calculation results. However, this simplification is chosen so that inaccuracies only exist for stack 1 ratings as unacceptable, so that stacks rated as acceptable always meet all arrangements at least with respect to the positional accuracy of electrode 2.

[0049] For this purpose, in the first inspection step, it is assumed that it is inspected whether the maximum edge-to-edge distance (K_W_R_TD) existing between the edges of the specific pair of cathodes 2b on the side surface of the laminate 1 is smaller than the first tolerance value (K_W_R_TDmax). In this case, the laminate 1 is evaluated as unacceptable in the negative case (K_W_R_TD≧K_W_R_TDmax), and in the positive case (K_W_R_TD<K_W_R_TDmax), the second inspection step is carried out.

[0050] In the second inspection step, it is inspected whether the maximum edge-to-edge distance (K_W_R_TD) is smaller than the value obtained on the one hand from the sum of the shortest dimensions (length or width) (K_W_R_min) of all cathodes of the laminate with respect to the calculation direction and on the other hand from the difference between the second tolerance value (T_G) and half of the overhang (v_R). As the overhang (v_R), here, half of the value by which the maximum edge-to-edge distance (K_W_R_TD) is smaller than the first tolerance value (K_W_R_TDmax) is defined. The second tolerance value (T_G) can here correspond to the maximum positional deviation defined (considered in the extension direction between the side surfaces of the pair) as acceptable with respect to the edges of the cathode 2b. If this second inspection step results in a negative inspection result (K_W_R_TD≧(T_G - v_R)+K_W_R_min), the laminate is evaluated as unacceptable. In contrast, if the second inspection step results in a positive inspection result (K_W_R_TD<(T_G - v_R)+K_W_R_min), the laminate is evaluated as acceptable.

[0051] To determine the edge position within the second calculation step and further calculation and inspection steps, it is not necessary to capture this edge over its entire length using X-rays. Rather, two different sections of the edge can be determined in succession (see FIGS. 10-14), and the associated partial results can be combined to calculate the individual edge profile. For this purpose, the stack 1 can be moved in a targeted manner through the linear capture areas of two linear detectors 10, which together represent the X-ray detector 8, as shown in FIGS. 10-14. In FIGS. 10-14, the edge sections still being captured in each capture step are shown with right-leaning shading, while the edge sections already captured are shown with left-leaning shading. Moving the battery cell stack 1 through the capture areas of the linear detectors 10 results in a flat capture area. This also allows for simultaneous capture of the edges assigned to two pairs of opposite sides of the stack 1. In the embodiment according to FIGS. 10-14, the linear detectors 10 are arranged in the form of mutually perpendicular crosses. Other arrangements are possible as well, for example L-shaped. The movement of the stack 1 is aligned vertically with respect to the capture area of ​​one of these linear detectors 10, respectively.

[0052] Based on the simplified calculation results of the second calculation step, it is possible to additionally inspect the stack 1 that was deemed unacceptable in the second calculation step and the corresponding first and second inspection steps in a third inspection step, in which a more complex inspection of the type of computed tomography is performed. For this purpose, the stack 1 according to FIG. 16 , fixed to the workpiece support 11, is positioned within the field of the X-ray 9 so that at least one edge of the stack 1 extending along the stacking direction 4 is captured. By rotating the stack 1 around the rotation axis 12, shadows of the X-ray 9 passing through this edge are determined at multiple positions on the stack, and the relative positions of the corners of the battery cell layers that form this edge of the stack 1 are determined based on the shadows. In this regard, FIG. 17 shows an example of an image generated based on the X-ray 9 captured from a section of the stack 1 that includes the considered edge.

[0053] Preferably, this third inspection step is performed on at least two edges of the stack 1, where if there are only two edges inspected, they should be diagonally opposite each other in the stack 1.

[0054] Based on the edge positions determined in the third inspection step, it is then further checked whether they are within a defined tolerance range, whereby if negative, the laminate 1 is evaluated as rejected, and if positive, the laminate 1 is evaluated as acceptable. The third inspection step is therefore used to verify whether the laminate 1 determined in the second calculation step and the corresponding first and second inspection steps as unacceptable and thus potentially unsuitable for use in battery production is actually unsuitable and therefore rejected, or whether it has simply been graded as unacceptable based on a simplification based on the first and second inspection steps. Such a grading is then considered by the third inspection step, thereby preventing the laminate 1 suitable for battery production from being treated as rejected. [Explanation of symbols]

[0055] 1. Laminate 2 electrodes 2a Anode 2b cathode 2b' First cathode 2b'' Second cathode 2b''' Third cathode 3 Separator 4 Lamination direction 5. Camera 5a Camera capture area 6 Measuring probes 7 X-ray irradiator 8 X-ray detector 9 X-ray 9a Central beam of X-rays 10 Linear detector 11 Workpiece support 12 Rotation axis AA Anode stacking area A K Cathode stacking area A S Separator lamination area S A Optimal anode edge location S K Optimal location of cathode edge S S Optimal position of separator edge d AK The minimum spacing distance between the anode and cathode edges of the battery cell d AS The minimum spacing distance between the anode edge and the separator edge of the battery cell d max The maximum spacing distance between the edges of all anodes that are present in the same way. K_W_R_TD Maximum edge spacing distance of cathode for stack side pairs K_W_R_TDmax First tolerance value K_W_R_min The shortest dimension of the cathode relative to the stack side pair T_G Second tolerance value v_R Overhang amount

Claims

1. A method for testing a stack (1) of multiple battery cell layers in the form of an anode (2a) as a first type of electrode (2), a cathode (2b) as a second type of electrode (2), and a separator (3), comprising: The battery cell layers have polygonal large area portions and are stacked along a stacking direction (4) aligned perpendicular to the large area portions, wherein: In a first calculation step, the geometry of at least one large area portion of at least the anode (2a) and / or the cathode (2b) is determined, In the lamination step, the battery cell layer is laminated on the laminate (1), Subsequently, for position inspection of the anode (2a) and / or the cathode (2b), In a second calculation step, the stack (1) is irradiated with X-rays (9) emitted by an X-ray irradiator (7) and detected by an X-ray detector (8), the X-rays (9) being aligned vertically with respect to a large area portion of the battery cell layer, and the detected X-rays are used to determine a maximum edge spacing distance (K_W_R_TD) existing between edges of the anodes (2 a) and / or cathodes (2 b) of at least one pair of opposing sides of the stack (1); In a first test step, it is checked whether the maximum edge separation distance (K_W_R_TD) is smaller than a first tolerance value (K_W_R_TDmax), wherein: If negative, the laminate (1) is rated as unacceptable, If so, a second testing step is performed, in which: In the second inspection step, a protrusion amount (v_R) is defined as half of the value where the maximum edge spacing distance (K_W_R_TD) is smaller than the first allowable error value (K_W_R_TDmax); It is checked whether the maximum edge spacing distance (K_W_R_TD) is smaller than a value determined from the sum of the shortest dimension (K_W_R_min) of all the anodes (2a) and / or all the cathodes (2b) in the calculation direction and the difference between a second tolerance value (T_G) and half the overhang (v_R), If negative, the laminate (1) is rated as unacceptable, If positive, the laminate (1) is evaluated as acceptable.

2. 2. The method according to claim 1, wherein in the first calculation step, the positions of edges forming all or only some of the corners of the anode (2a) and / or the cathode (2b) are determined.

3. 3. The method according to claim 1 or 2, wherein the second calculation step and the first and second inspection steps are performed for at least two pairs of opposite sides of the stack (1).

4. Only one type of electrode (2) is inspected according to the second calculation step and the first and second inspection steps, and in a further calculation and inspection step, the stack (1) is irradiated with X-rays (9) that are irradiated by an X-ray irradiator (7) and detected by an X-ray detector (8), the X-rays (9) being aligned vertically with respect to a large area portion of the battery cell layer, and the X-rays detected with respect to at least one side of the stack (1) are used to calculate the maximum spacing distance (d) that exists between the edges of all electrodes (2) of the other type assigned to that side of the stack (1). ｍａｘ ) is calculated, and based on the calculated value, the distance (d ｍａｘ ) are each checked to see if they are less than a third tolerance value, where: If negative, the laminate (1) is evaluated as unacceptable or rejected, If positive, the laminate (1) is evaluated as acceptable.

3. The method according to claim 1 or 2.

5. If the laminate (1) is evaluated as unacceptable, in a third inspection step the laminate (1) is additionally inspected for the maintenance of at least one tolerance range, If negative, the laminate (1) is evaluated as rejected, If positive, the laminate (1) is evaluated as acceptable.

3. The method according to claim 1 or 2.

6. 6. The method according to claim 5, wherein in the third inspection step, the stack (1) is irradiated with X-rays (9) which are irradiated by an X-ray irradiator (7) and detected by an X-ray detector (8), and the orientation of the stack (1) relative to the X-rays (9) is selected so that at least one edge of the stack (1) extending along the stacking direction (4) is completely captured by the X-rays (9) in at least two different positions, and on the basis of which the relative positions of corners of at least the anode (2a) and / or the cathode (2b) forming said edge of the stack (1) are determined.

7. The method of claim 1 or 2, wherein after stacking the battery cell layers in the stacking step, the battery cell layers are inspected for the presence of buckles.

8. 8. The method of claim 7, wherein the buckle inspection is performed by determining and evaluating the geometry of the battery cell layers and / or by determining and evaluating the geometry of the stack (1).

9. 3. The method according to claim 1 or 2, wherein determining the geometry of the battery cell layers and / or determining the geometry of the stack (1) is performed using an optical camera system.

10. The method of claim 9 , wherein the camera system images are recorded in a top view of a large area portion of the battery cell layer.

11. 11. The method according to claims 8 and 10, wherein the geometry of the battery cell layers is determined after they are placed on the stack (1) to be formed, respectively.

12. 10. The method according to claims 8 and 9, wherein images of the camera system are recorded in a side view with respect to the stack (1) to determine the geometry of the battery cell layers in the formed stack (1).

13. 9. The method of claim 8, wherein determining the geometry of the stack (1) comprises determining the height of the stack (1) at multiple locations.

14. The method of claim 13 , wherein the determining of the height is performed mechanically.

15. A method as described in claim 1, wherein in the second calculation step, relative movement occurs between the stack (1) and the X-ray (9).

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