Technical Field

The present disclosure relates to a method and apparatus for testing or inspecting the quality of manufacture of a battery cell. In particular, the present disclosure relates to a method and apparatus for determining an alignment of stacked electrode layers.

Background

Rechargeable or “secondary” battery cells find widespread use as electrical power supplies and energy storage systems, for example in automobiles. Several different form factors exist for such battery cells depending on their intended application field. In automotive applications, the most common cell form factors are cylindrical, prismatic and pouch cells.

A battery cell stores electrical energy in an electrode assembly, which may be comprised of stacked electrode layers or sheets, which may be folded and/or rolled and referred to as an “electrode roll” or a “jelly roll”. The electrode sheets may include an anode sheet, a cathode sheet, and a separator sheet arranged between the anode sheet and the cathode sheet.

During or after the manufacture of battery cells, tests and inspections may be carried out to assess the quality of the battery cells as a whole or constituent components thereof. A particularly important quality to be assessed is the relative position or alignment of stacked electrode layers or sheets.

Conventional techniques for assessing such a quality may involve the use of industrial radiography such as X-rays or computed tomography scanning, or ‘CT scanning’, which utilizes X-ray equipment to image components externally and/or internally. Such techniques are preferred for assessing the manufacturing quality of battery cells because they are nondestructive and can be performed ‘in-line’ during a manufacturing process for the battery cells. Summary

It is realized as a part of the present disclosure that conventional approaches to quality testing for electrode stacks are slow and cumbersome and may be a delaying bottleneck for an overall manufacturing process for a battery cell. Moreover, such approaches may lack the required precision for determining an alignment between electrode sheets, as this alignment may often be a safety-critical factor for battery cells. For example, according to some conventional approaches, only the corner of the electrode assembly may be analyzed.

Therefore, according to aspects of the present disclosure described herein, a new and advantageous approach is defined, having an optimal tradeoff between speed of performance of the quality testing and the precision and accuracy of the result.

In essence, the present approach involves the identification of multiple locations on the edges of stacked electrode layers or sheets and the interpolation therebetween and/or extrapolation therefrom so as to arrive at a determination of an alignment of electrode sheets that takes into account the entire length of an edge, rather than just a corner. Hence, it is possible to determine a closest approach between, e.g., an anode and a cathode electrode sheet, even if the area where this occurs is not directly imaged.

In particular, according to an aspect of the present disclosure, there is provided herein a method for determining an alignment of a stack of at least two electrode layers, wherein the method comprises obtaining at least two images (or ‘views’) of the electrode layers, each image having an imaging plane, which may preferably be orthogonal to the plane of the electrode layers. Put another way, the at least two images have an imaging plane (a plane defined by the focal point and/or visual field of the image) that is preferably parallel to the stacking direction of the stack. These images are preferably cross-sectional images, such as those taken by X-ray imaging devices or as slices of a computed tomography (CT) scan. That is, the images may be radiographic images or the like.

According to this method, a first edge and a second edge of the electrode layers are imaged in the at least two images, the first edge being adjacent to the second edge. The electrode layers may be rectangular in shape such that each layer may have four peripheral edges and four comers. Corresponding edges in stacked layers may therefore be the edges that run along a same side of the stack.

According to the presently described method, an alignment of the electrode layers is determined based on the relative locations of each edge in the at least two images.

By using (at least) two images of the stack, and establishing the relative locations of an imaged edge in the images, the accuracy of the alignment determination can be greatly improved. For example, in a case where a closest approach between corresponding edges of layers is a safety- critical measurement for a battery cell (e.g., where the layers are an anode and a cathode sheet), prior art techniques would attempt to directly image the location at which this closest approach was expected to occur. However, according to the presently described approach, the location at which the closest approach occurs can be deduced from an interpolation or extrapolation of the locations of the imaged edges of the electrode layers. Thus, the shortest distance between electrode layers (as an example metric of their alignment) can be determined even if the location at which this occurs is not directly measured.

Furthermore, as two adjacent edges are imaged, an intersection of these two edges can also be deduced from the relative locations of the imaged edges in the images. That is, for each layer, a relative position of the corner of the layer can be established. For cases wherein electrode layers are misaligned with each other, the location at which this misalignment will be most apparent will be at the comers and thus an ability to deduce the intersection of the two adjected imaged edges further enhances the accuracy of the determination of the alignment of the electrode layers.

Moreover, knowing that the two edges are adjacent edges, and therefore can be interpolated to an intersection, the orientation/alignment of the stack relative to an imaging arrangement capturing the images does not need to be precisely controlled. That is, by employing a geometric analysis to the relative locations of the imaged edges in the images, and knowing that the adjacent edges intersect, the alignment of the stacked electrode layers can be determined without requiring further information in respect of the stack’s alignment relative to the imaging planes. Therefore, the time-consuming task of precisely aligning the stack to an imaging arrangement can be skipped without impacting the accuracy of the determination of the alignment of the stacked electrode layers. Accordingly, a faster throughput of electrode stacks can be achieved for the presently described method, allowing for an overall increase in rate of production for battery cells.

Determining an alignment of the electrode layers based on the relative locations of each edge may comprise any suitable mathematical (i.e. , geometric) analysis. For example, this may be performed by determining, based on the relative locations of each edge in the at least two images a line corresponding to said each edge, and determining an alignment of the electrode layers based on the determined lines corresponding to the first edge and the second edge.

The determined lines may be expressed visually, mathematically, or otherwise, such as through the generation of a line equation for each edge in a co-ordinate space for determining alignment of the stack. The alignment coordinate space may be determined based on a predetermined relative arrangement of the stack and one or more of the imaging planes, a predetermined relative arrangement of the imaging planes relative to each other, and/or a determined relative arrangement of the imaging planes, which may be based on a known angle of intersection of the two adjacent sides or a determined intersection of an imaging plane with the electrode stack.

The determined lines for each edge of each layer may therefore be interpolated or extrapolated so as to establish a relative arrangement of corresponding edges of the layers along the entire length of the layers. Therefore, a location at which a shortest distance between corresponding edges occurs can be accurately and rapidly determined.

Determining a line corresponding to an edge of an electrode layer may comprise determining a first location of the edge of the electrode layer in a first image of the at least two images, determining a second location of the edge of the electrode layer in a second image of the at least two images, and determining, based on the first location and the second location, the line corresponding to the edge of the electrode layer.

Determining a location of an edge of an electrode layer in an image may comprise applying edge detection processing or similar such processing to the image. The determined locations of the edges may be expressed as co-ordinates, e.g., in the co-ordinate system of the imaging plane of the image, the other image, or the stack, depending on the implementation.

In some examples, the images may be pre-aligned relative to each other, i.e. , with a known relationship between the imaging planes. Therefore, the location of a same edge of a same layer may be directly compared in two images according to a co-ordinate system for the image (e.g., in units of pixels) so as to determine a relative location of the edge in the images.

That is, determining a line corresponding to an edge of an electrode layer may be further based on a predetermined relative orientation of and/or spacing between the respective imaging planes of the at least two images. Alternatively, as mentioned above, the relative orientation of and/or spacing between the respective imaging planes of the at least two images may be determined based on the relative locations of imaged edges in the images, which may also include an assumption that, e.g., the angle of intersection of the imaged edges is known and/or that the edges are straight.

The first edge and the second edge of the electrode layers may be adjacent to respective (and corresponding/overlapping) corners of the electrode layers. Accordingly, determining an alignment of the electrode layers may comprise explicitly determining a corner location of at least one of the comers of the electrode layers, and basing the determination of the alignment between the first electrode sheet and the second electrode sheet further on this corner location.

The corner location may be expressed as a co-ordinate, which may be in a co-ordinate system for the stack (which may be two- or three- dimensional). It may be established firstly whether the corner location of a first layer is within the boundary of a second layer adjacent to the first layer. If this is not the case, then it may be determined that the first and second layers and severely misaligned such that the corner of one of the layers is extending over the edge of the other layer. However, if the corner of the first layer is within the boundary of the second layer, then it may be assumed that the closest approach between the first and second layers will be between a corner of the first layer and an edge (or a corner) of the second layer. Accordingly, determining the corner location for the layers is particularly useful for an accurate determination of the alignment of said layers.

Determining an alignment of edges of the electrode layers may comprise determining a shortest distance between corresponding edges of the electrode layers, which may then be compared with some threshold tolerance value. It will be appreciated that the ‘shortest distance’ in this context refers to the distance as measured within the plane of one of the layers, i.e., orthogonal to the stacking direction of the layers.

For example, it may be a requirement, for the safe operation of a battery cell, that corresponding edges of stacked electrode layers are not closer than 5 millimeters (mm) to each other. Therefore, if it is determined that the shortest distance (or ‘closest approach’) between the edges of the stacked layers is 4 mm, then it may be determined that the layers are out of alignment. According to the advantageous approach described herein, neither of the images may directly capture the location at which the edges of the layers are 4 mm apart from each other, but this information may be determined based on the relative locations of the edges in the images.

A position and/or orientation of at least one of the imaging planes may be predetermined to ensure imaging of two edges of the electrode layers. That is, the imaging planes may be positioned/oriented so as to ‘aim’ for a substantially central position along the target edges, such that an imprecise positioning of the stack relative to the imaging arrangement capturing the images does not risk the imaging planes completely missing the stack such that no (or not enough) edges are imaged.

Alternatively, one or more of the imaging planes may be dynamically determined based on a visibility of an edge of an electrode layer in the image resulting from said imaging plane. For example, if an image resulting from a particular imaging plane does not contain any or enough edges to perform the alignment determination method, then the imaging plane may be moved in a direction that is expected or determined to yield an image that images the stack correctly.

According to some examples, the method may further comprise obtaining a further image having a determined imaging plane based on a predicted location of the shortest distance between corresponding edges of the electrode layers. Thus, the value of the shortest distance between corresponding edges of the electrode layers may be more precisely determined through direct imaging using only (a minimum of) three images, assuming that neither of the first two images captures this location already.

The stack may comprise only two electrode layers such as two electrode sheets or a foil and a coating, or the stack may comprise three or more electrode layers. In this latter case, an alignment may be determined for each electrode layer in the stack, relative to each adjacent electrode layer in the stack. That is, a determinative factor in determining whether a stack of electrode layers is aligned may be a determination that each layer is suitably aligned with the electrode layers immediately neighboring it, i.e. , above and below it (unless the layer is the top or bottom layer).

Therefore, the alignment determination may be performed for each pair of neighboring layers in a stack, and these determinations may be performed in sequence or in parallel. In some examples, if even one pair of electrode layers is out of alignment, then the entire stack may be identified as being of too poor a quality.

According to some examples, the method may further comprise identifying an electrode layer in an image of the stack and identifying the same electrode layer in another image of the stack, based on a stacking location of the electrode layer relative to other imaged electrode layers, or based on a location of said electrode layer in the image and the other image.

That is, the same edge of the same layer may be identified in different images by identifying that the edge is at a same height (e.g., in terms of pixels) in the image, assuming that a vertical positioning of the imaging planes for the images is aligned. Alternatively, the imaged layers may be counted such that a layer may be identified according to the number of layers above and/or below it, which may require an assumption that the entire stack has been imaged in both images.

The method described herein may be performed by a processing device comprising means for carrying out the method. The method may be implemented as a computer program comprising instructions which, when the program is executed by a processing device, cause the processing device to carry out the method. The processing device may be any suitable computing device, which may be remote from or integrated as a part of a same system as an imaging apparatus that captures the images.

That is, according to another aspect of the present disclosure, there is provided a system, comprising a processing device configured to perform the above-described method, and an imaging apparatus configured to generate images of a stack of electrode layers and provide the images to the processing device. The processing device and the imaging device may be communicatively coupled in any suitable manner, such as by wired and/or wireless links.

The imaging device may comprise a radiographic, ultrasonic, or other imaging device configured to generate, in an advantageously non-destructive manner, cross-sectional images or views of the layers of the stack. In an example, the imaging device may be a CT scanner and the processing device or some other device in the system may comprise means for generating images from ‘slices’ of a CT scan generated of all or at least a relevant part of the stack of electrode layers.

Such a system may be installed as part of a manufacturing arrangement for manufacturing a battery cell or parts thereof. The system may preferably be configured for a high throughput of stacks of electrode layers such that the advantages of rapid, yet accurate determination of alignment provided by the presently described approach may be most fully realized.

In any event, numerous advantages, some of which are described above, may be realized through the use of multiple images of the edges, and the imaging of two adjacent edges of stacked sheets. These advantages, as well as others, may be further appreciated through a description of specific illustrated embodiments.

Brief Description of the Drawings

One or more embodiments will be described, by way of example only, and with reference to the following figures, in which:

Figure 1 A schematically shows a stack of electrode layers;

Figure 1 B schematically shows a cross-sectional view of the stack of electrode layers shown in figure 1A;

Figure 2 schematically shows another process for determining an alignment of a stack of electrode layers, according to another example implementation of the present disclosure;

Figure 3 schematically shows another process for determining an alignment of a stack of electrode layers, according to another example implementation of the present disclosure;

Figure 4 schematically shows a process for determining a shortest distance between the edges of stacked electrode layers, according to an example implementation of the present disclosure;

Figure 5 schematically shows another process for determining an alignment of a stack of electrode layers, according to another example implementation of the present disclosure;

Figure 6 illustrates a method for determining an alignment of a stack of electrode layers according to an example implementation of the present disclosure;

Figure 7 schematically shows an imaging apparatus for imaging stacks of electrode layers; and

Figure 8 schematically shows a system for determining an alignment of a stack of electrode layers according to an example implementation of the present disclosure. Detailed Description

The present disclosure is described in the following by way of a number of illustrative examples. It will be appreciated that these examples are provided for illustration and explanation only and are not intended to be limiting on the scope of the disclosure.

Figure 1A schematically shows a stack 100 of electrode layers 102, 104, which may be a component for the manufacture of a battery cell such as an automotive battery cell.

The uppermost two layers 102, 104 are visible. A first electrode layer 102 is sized larger than the second electrode layer 104 and the layers 102, 104 are aligned relative to each other. The layer 102 may be an anode sheet (e.g., a coated or uncoated metal foil or the like) and the layer 104 may be a cathode sheet (e.g., a coated or uncoated metal foil or the like), in which case a separator (not shown) is placed between the layers 102, 104 to prevent electrical contact between the cathode and anode sheets. In another example, the layer 102 may be a metal foil for an electrode sheet and the layer 104 may be a coating thereon.

Each layer 102, 104 is rectangular and thereby comprises four edges 102a-d, 104a-d and four comers. The cross-section A-A is shown in figure 1 B. It can be seen therein that the stack 100 of electrode layers 102, 104 is comprised of six layers 102-1...6 of a first type and six layers 104-1...6 of a second type. In the illustrated example, the edges of all layers 102, 104 of a corresponding type are aligned with each other. This may be a preferred state for a stack of electrode sheets.

However, during assembly of a battery cell and, namely, the stack 100 of electrode layers 102, 104, some layers 102, 104 may be misaligned - e.g., translationally and/or rotationally relative to each other. Accordingly, the operational life of the resultant battery cell may not be as long as a battery cell having better aligned electrode layers 102, 104. For example, an anode sheet may be misaligned relative to a (smaller underlying or overlying) cathode sheet in a stack of electrode sheets such that their edges are closer together than a minimum safe distance. It is preferred that any such malformed stacks are identified in an accurate and rapid manner. Accordingly, figure 2 schematically shows a process for determining an alignment of a stack 100 of electrode layers 102, 104, according to an example implementation of the present disclosure.

In particular, figure 2 shows a stack 100 of electrode layers 102, 104, of which two images 106a, 106b are taken using respective imaging planes 108a, 108b, these being illustrated relative to the stack 100.

The images 106a, 106b may be obtained by positioning an imaging device according to the imaging planes 108a, 108b or by taking slices of a CT scan of the stack 100 according to the imaging planes 108a, 108b or by some other means. It will be appreciated that, although the imaging planes 108a, 108b are shown as being lines, they extend in two dimensions, with the imaging planes 108a, 108b being orthogonal to the plane(s) of the layer(s) 102, 104, in this example.

Each image 106a, 106b shows a first edge 102a of the first electrode layer 102, a first edge 104a of the second electrode layer 104, a second edge 102b of the first electrode layer 102, and a second edge 104b of the second electrode layer 104.

It will be appreciated that a spacing in the y’ and y” direction in the images 106a, 106b, between the layers 102, 104, may be emphasized in this illustration. In some examples, however, such an apparent spacing may result from a separator sheet or the like being arranged between the layers 102, 104 but not being visible in the image 102, 104 (e.g., if the separator sheet is transparent to the imaging wavelength).

Edge detection processing may be applied to the images 106a, 106b so as to identify the locations 110a-h of the edges 102a-b, 104a-b. The relative locations 110a, 110b of the first edge 102a of the first electrode layer 102 in the first image 106a and the second image 106b may, for example, allow for a determination of a line 112a corresponding to said edge 102a in an alignment co-ordinate space 111. Lines 112b, 112c, 112d may also be determined for the remaining imaged edges 102b, 104a, 104b so as to allow for a determination of an alignment between the first electrode layer 102 and the second electrode layer 104. The determination of the alignment may be carried out by comparing the relative locations 110a-h of the imaged edges 102a-b, 104a-b, which may involve a comparison of the lines 112a-d in the alignment co-ordinate space 111.

In the example shown in figure 2, the relative spacing between the imaging planes 108a, 108b may be known, and it may be known that these imaging planes 108a, 108b are also parallel to each other such that a coordinate space (x’, y’, z’) for the first image 106a can be calibrated relative to the co-ordinate space for the second image 106b (x”, y”, z”), wherein it will be appreciated that y’ and y” are aligned with the z axis in the stack coordinate space. It will be further appreciated that the relationship between the stack co-ordinate space (x, y, z) and the alignment co-ordinate space 111 may not be relevant to or necessary for a determination of alignment between the electrode layers 102, 104.

Figure 3 shows an example wherein the relative positioning/orientation of the imaging planes 108a, 108b is non-parallel, and may not be known when determining the alignment between the electrode layers 102, 104.

According to this example, the co-ordinate space (x’, y’, z’) of the first image 106a and the co-ordinate space (x”, y”, z”) of the second image 106b may share a common axis in that the imaging planes 108a, 108b are both orthogonal to the plane of the layers 102, 104, and therefore y’ = y” = z.

It may be assumed that both of the imaging planes 108a, 108b intersect with, e.g., the first electrode layer 102 at a common y co-ordinate in the stack co-ordinate space, or this may be enforced so as to orient the alignment co-ordinate space 111 with at least one of the layers 102, 104 being horizontally aligned.

The images 106a, 106b may also have some correspondence between the number of pixels in the image and a real measurement of the stack 100, such as 10 pixels equaling 1 mm.

One or more assumptions or constraints may be applied, such as the edges 102a-b, 104a-b being straight or parallel, the layers 102, 104 having right-angled or known angled comers, etc. such that lines 112a-d may be conceived in the alignment co-ordinate space 111 corresponding to the edges 102a-b, 104a-b of the electrode layers 102, 104.

It can be seen that, for example, line 112a extends between the locations 110a and 110b in the alignment co-ordinate space 111 , and line

5 112c extends between the locations 110e and 110f, and these lines 110a, 110c intersect at a right-angle at a determined corner co-ordinate 114a corresponding to the corner of the electrode layer 102. Similar lines 112b and 112d, and corner 114b, are determined corresponding to the edges 104a, 104b and corner of the other electrode layer 104. The alignment between the 0 electrode layers 102, 104 may therefore be determined based on these determined locations 110a-h and, more particularly, based on their relative locations in the two images 106a, 106b.

Although only two layers 102, 104 are shown and discussed in relation to figures 2 and 3, it will be appreciated that a stack 100 of many layers may 5 also be analyzed in an analogous way. In such examples, each layer may have its alignment determined only for each immediately adjacent layer (e.g., directly above and below in the stack 100). Each layer may be one of two types, wherein a first type (like layer 102) may be larger sized, and a second type (like layer 104) may be smaller sized, such as shown the stack 100 0 shown in figure 1 B. It will be appreciated that, in some examples, the sizes of the layers 102, 104 may instead be the same.

The locations 110a-h may be expressed as co-ordinates in the image co-ordinate space or transformed into the common alignment co-ordinate space 111 , such that a list of data may be generated from edge detection 5 performed on the images 106a, 106b, corresponding to the detected locations of each edge of each layer:

Once all edge end points have been detected, a transformation may be applied to some or all of the co-ordinates, such as a mapping of (x’, y’, z’) to (x”, y”, z”), or a mapping of both co-ordinate spaces to a common alignment co-ordinate space. Such a mapping may be based on knowledge in respect of the relative spacing/orientation of the imaging planes used to obtain the images, assumptions in respect of the properties of the stack (e.g., straightness of edges, angle of intersection of the edges of the imaged layers), and/or other assumptions or determinations, depending on the implementation.

Determined locations (e.g., expressed as a co-ordinate) from both images, corresponding to a same edge of a same layer - for example, (x’i , y’i, z’i) and (x”i, y”i, z”i) - may then be used to define or derive a line equation corresponding to said edge. Determined lines corresponding to intersecting edges may further be used to derive a corner co-ordinate at which the edges intersect. Based on these determinations, the alignment between layers may be determined.

The alignment of electrode layers 102, 104 may be assessed through a number of different metrics. For example, a preferred metric may be the closest distance of approach between corresponding edges 102a-d, 104a-d of the electrode layers 102, 104. An example of such an approach is illustrated in figure 4.

In figure 4, lines 112a, 112b, 112g, and 112h are calculated in a coordinate space, corresponding to two adjacent sides of two electrode layers. Lines 112a and 112g extend to a corner co-ordinate representing a determined location of the corner of an electrode layer, for example an anode sheet. Lines 112b and 112h extend to a corner co-ordinate representing a determined location of the corner of another electrode layer, for example a cathode sheet stacked upon the anode sheet. Based on these calculated lines 112a, 112b, 112g, 112h and corner co-ordinates, a shortest distance between the edges of the electrode layers can be determined. In this example, it can be assumed that, if the electrode layers are not so misaligned as to cross their edges, then a corner of the smaller-sized electrode layer will be the closest part of the edge to the larger- sized electrode layer.

By considering the co-ordinate of the corner of the smaller-sized layer and the line 112a, a line L can be conceived therebetween, which is perpendicular to the line 112a. The length of this line L will correspond to the shortest distance between the edges of the electrode layers.

The determined shortest distance between the edges of the electrode layers may be compared with a minimum or threshold distance, which may be predetermined based on safety requirements, electrical properties of the electrode layers, desired precision, etc. If the determined distance between the edges of the electrode layers is determined to be outside of an acceptable range, the stack of electrode layers may consequently be identified as being malformed or faulty, and the stack may thus not continue to being made into a battery cell.

Stacks may have identifiers such as barcodes, NFC tags, or the like that allow for their unique identification. A determination that a stack is defective/malformed may result in an association of this determination with the stack’s identifier so that it can be swiftly identified and removed from the production line. In some examples, this process may be entirely automated in-line in the manufacturing process for a battery cell. Defective/malformed electrode stacks may be recycled or otherwise disposed of.

As the determination of misalignment of electrode layers is advantageously made based on a precise measurement of a closest distance between the edges of the electrode layers, a grading scheme may be applied, instead of a binary assessment of defective or non-defective. For example, an only-slightly-misaligned stack of electrode layers may be used in an end product that has lower quality requirements.

Figure 5 shows an example of the present disclosure wherein lines 112a-112h corresponding to each edge, and corners 114a-h, of the rectangular electrode layers are determined. Such a determination is performed through the use of four images, the respective imaging planes 108a-d of which are shown schematically overlaid onto the alignment coordinate space to illustrate the intersections with the edges of electrode layers of the stack.

In this example, a first pair of imaging planes 108a-b is selected to intersect two adjacent edges (e.g., edges 102a-b, 104a-b as shown in figure 1A), and a second pair of imaging planes 108c-d is selected to intersect the remaining two adjacent edges of the rectangular electrode layers (e.g., edges 102c-d, 104c-d as shown in figure 1A). Based on these four images, a complete determination of the relative positions/alignments of each edge can be made and, consequently, the alignment of the electrode layers can be accurately determined.

Figure 6 schematically illustrates an example method 600 for determining an alignment of a stack of at least two electrode layers.

Step S101 of the method 600 comprises obtaining at least two images 106 of the electrode layers, each image having an imaging plane orthogonal to the plane of the electrode layers, although the imaging plane may be angled differently in some examples. A first edge and a second edge of the electrode layers are imaged in the at least two images 106, the first edge being adjacent to the second edge.

According to this example, the method 600 further comprises, at step S102, determining the locations 110 of the electrode layer edges, which may be achieved using edge detection processing or the like applied to the images 106.

Furthermore, according to this example, the method further comprises, at step S103, determining lines 112 corresponding to the electrode layer edges. The lines 112 may be interpolated between the determined locations 110, and/or extrapolated beyond the determined locations 110. For example, the lines 112 may be extended to what is expected to correspond to an entire length of an edge represented by the lines 112. Finally, at step S104 of the method 600, an alignment of the electrode layers is determined, based on the relative locations 110 of each edge in the at least two images 106, e.g., based on the determined lines 112.

Figure 7 schematically shows an imaging apparatus 200 for imaging stacks 100 of electrode layers, according to an embodiment of the present disclosure.

The imaging apparatus 200 may be part of an in-line manufacturing process for a battery cell, at a stage after the manufacture of the stacks 100 of electrode layers. The stacks 100 may be fed, e.g., by a conveyor system 250 or otherwise, into an imaging enclosure 201 , and arranged on a mounting 202. The mounting 202 may be a surface such as a table or a frame or holder that may be rotatable or pivotable.

The arrangement of the stack 100 on the mounting 202 may be performed manually or automatically, e.g., using robotic manipulators or the like. As discussed above, according to the techniques described herein, the precision of the arrangement of the stack 100 is less important for the precision of the determination of the alignment of the electrode layers in the stack 100. Therefore, the speed with which a stack 100 can be fed into the imaging apparatus 200 and arranged in place on the mounting 202 can be improved.

Once arranged on the mounting 202 in the imaging enclosure 201 , the stack 100 can be imaged by imaging devices 204 arranged around the stack. The placement of these imaging devices 204 may be fixed or moveable and may be selected/adapted depending on the intended imaging plane(s) for imaging the stack 100. The imaging devices 204 may comprise radiographic imaging devices such as X-ray systems for generating a CT scan.

The stack 100 may be rotated or otherwise moved relative to the imaging devices 204 during the imaging, e.g., to obtain a plurality of radiographic images and thereby create a three-dimensional CT scan of the stack. The mounting 202 may further comprise components or indicators for aligning the stack 100 with the imaging devices 204 such as ridges, engravings, or the like. In some examples, the imaging apparatus 200 may only be configured to generate images which are then provided to a processing device for processing in accordance with the techniques described herein. However, in other examples, a system may comprise an imaging device and a processing device together.

Figure 8 schematically shows an example of such a system 300. The system 300 comprises an imaging device 302 which may be similar to all or a part of the imaging device 200 shown in figure 9. The system further comprises a processing device 304 for processing the images in accordance with the techniques described herein. The imaging device 302 may be directly or indirectly connected to the processing device 304 such that the processing device can obtain, from the imaging device 302, the images generated thereby.

The processing device 304 may thereafter perform the method for determining the alignment of the stacked electrode layers in accordance with the techniques described herein.

While the present disclosure is susceptible to various modifications and alternative forms, specific embodiments are shown and described by way of example in relation to the drawings, with a view to clearly explaining the various advantageous aspects of the present disclosure. It should be understood, however, that the detailed description herein and the drawings attached hereto are not intended to limit the disclosure to the particular form disclosed. Rather, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the following claims.