Method for testing the quality of an electrode-separator assembly under manufacture

Abstract

Method for testing test criteria of an electrode-separator assembly (1), ESV, with ESV sheets (10) comprising the separator (13), anode (11), and cathode sheets (12). The method determines the positions of various relevant areas of the ESV sheets using purely optical means, and can thus detect stacking faults during the production of an ESV (1).

Description

The invention relates to a method for testing a quality of an electrode-separator composite (ESV) being produced.An ESV comprises anode and cathode sheets alternately laid one above the other, between which a separator layer is arranged in each case. This separator layer is usually formed by individual separator sheets. The electrochemical performance of a battery cell comprising the ESV is critically dependent on the overlap of the ESV sheets, i.e. of the electrode sheets and separator sheets. Thus, this performance decreases more quickly with less electrode sheet coverage in the edge region of the ESV. In addition, a short circuit and the failure of the battery cell are triggered by a direct contact of an anode and cathode sheet in the event of a wrong deposition in the ESV. Furthermore, inaccurate stacking of the ESV sheets results in inhomogeneous voltage peaks during the charging process, so that pure lithium can deposit on the anode. These deposits form dimers that can puncture the separator sheet.Typically, the anode sheet of an ESV is peripherally somewhat larger than the cathode sheet to ensure complete coverage of the anode and cathode despite deposition inaccuracies and sheet size and geometry variations.There is an ever increasing tendency to reduce this overhang of the anode in order to save material.This means that the stacking process of the ESV is subject to increasing requirements with respect to the deposition accuracy. In addition, the stacking process is a Bottleneck in battery cell manufacturing, so that it is desirable to shorten a production time. However, as the process speed increases, the deposition accuracy decreases. For further optimization and development of stacking processes, the position, i.e. a position and orientation, of the ESV sheets in the ESV must thus be measured after completion.The position of the electrode sheets in the ESV is determined by means of computer tomographic (CT) imaging methods. However, there is the disadvantage here that certain materials of the anodes or cathode sheets (coating or substrate) do not have a CT contrast and thus remain invisible in the CT image.Furthermore, the use of CT systems requires complicated radiation protection measures, so that integration of a CT system into a production line entails a significantly increased complexity.In addition, the acquisition and the evaluation of the CT data is time-consuming and leads to a slowing down of the manufacturing process in a series production line, since each ESV has to be examined for predefined test criteria after completion.A simple optical examination during production, i.e. in particular after an ESV sheet is deposited, can lead to incorrect results in the finished ESV, since the depositing device which stacks the ESV sheets can itself contribute to already deposited ESV sheets slipping later, e.g. due to transverse forces which are exerted by the depositing device on the already deposited ESV sheets.On the one hand, this can lead to each ESV sheet successively having a slight displacement with respect to the preceding ESV sheet compared to previously deposited ESV sheets, which can lead to an obliquely stacked ESV in the sum of all ESV sheets. Another source of error that cannot be resolved with simple optical inspection is an acute slippage or mispositioning of a single ESV sheet with respect to the other ESV sheets and the workpiece carrier that occurs after deposition.Moreover, the step formation in which ESV sheets of the same type are deposited successively shifted in one direction is a problem which is not recognized with known purely optical systems.DE 10 2022 124 784 A1 discloses a system which is provided and configured for stacking ESV sheets. The system has various sensors, but cannot solve the above-mentioned problems.KR 10 2023 0 101 723 and DE 10 2022 102 764 A1 each disclose systems for partially optically controlling the deposition of ESV sheets in an ESV stack. However, both systems are not designed to overcome the aforementioned disadvantages.It is an object of the present invention to overcome these disadvantages and to provide a rapid, inexpensive and reliable method for checking the position of the ESV sheets in an ESV stack.The object is achieved according to the invention by a method according to claim 1.A first aspect of the invention relates to a method for checking test criteria of an electrode-separator composite, ESV, with ESV sheets comprising the following types of ESV sheets, separator and electrode sheets, the latter selected from the group comprising anode and cathode sheets, comprising the following steps: a) After in particular each deposition of an ESV sheet on the ESV and in particular before deposition of a further ESV sheet, a multiplicity of positions of selected regions of the deposited ESV sheet are determined, wherein at least the positions which are determined again in the following steps b) to d) are included in the multiplicity of positions, wherein the positions in a deposition plane of the ESV sheet are determined on the basis of a first optical recording in plan view, obliquely or perpendicularly to the deposition plane; b) after depositing all the ESV sheets on the ESV, a position of the separator sheets along an x-direction along which a first edge of the ESV extends is determined on the basis of a second optical recording of a first side view of the ESV; c) after depositing all the ESV sheets on the ESV, a position of the anode sheets along the x-direction and a y-direction of the ESV, wherein the y-direction extends along a second edge of the ESV, is determined on the basis of a third optical recording comprising a second and third side view of the ESV, d) After depositing all ESV sheets on the ESV, a position of an outer contour line of diverter tabs of the electrode sheets is determined, the position with respect to the y-direction being determined on the basis of a fourth optical recording of the ESV of at least parts of the deposition plane, wherein in step a) a check is made for each ESV sheet whether the ESV sheet lies in a tolerance range assigned to the type of the ESV sheet, wherein in steps b) to d) a check is made as to whether the ESV meets at least some predefined check criteria even after depositing all ESV sheets, wherein this check is positive, if all determined positions in steps b) to d) are still within the associated tolerance range for the respective position and type of ESV sheet, and negative if not all determined positions are within the associated tolerance range.According to the invention, steps b) to d) ensure that the predefined checking criteria are also fulfilled after all ESV sheets have been deposited.The method according to the invention makes it possible to determine the position of the ESV sheets during stacking of the ESV and to determine, immediately after depositing the last ESV sheet, whether the ESV sheets have changed their position after depositing, e.g. have slipped, displaced or twisted, or are furthermore within the associated tolerance ranges, so that the predefined checking criteria for the ESV are also fulfilled after depositing all ESV sheets.In step a), a plurality of positions at selected areas, such as corners or edges of each individual ESV sheet, are essentially determined, while the subsequent steps b) to d) serve to identify subsequently occurring deviations of the position and to estimate to what extent the position or position of the ESV sheets still meet the predefined checking criteria.The method can be carried out exclusively with optical recording means, so that a time-consuming computer tomographic examination can be omitted if the optical examination does not indicate any anomalies, i.e. if the predefined examination criteria are fulfilled after depositing all ESV sheets.The predefined test criteria are, on the one hand, geometric criteria which define tolerance ranges for the ESV sheets within which each ESV sheet must lie, and, on the other hand, the test criteria also relate to an order of the ESV sheets in the ESV and a position with respect to a workpiece carrier on which the ESV is stacked.A change in the order of the ESV sheets after depositing the ESV sheets is not to be expected, so that such a checking criterion does not have to be verified by means of steps b) to d). A deviation from the correct stacking sequence would already be detected in step a) and the method could be aborted.Steps b) to d), however, check at least one position parameter of each ESV sheet, so that a subsequent change in position can be ascertained on the basis of these checks.Thus, step b) checks the corner positions and, if appropriate, selected edge positions of the separator sheets, step c) the position of at least some corners of the anode sheets, and step d) the position of the collector tabs of the anode and cathode sheets.In particular, in steps b) and c) the position of only a single corner of the ESV sheets may be determined or several, in particular the positions of all four corners of the ESV sheets may be determined.This allows position changes of the ESV sheets to be determined which have occurred subsequently, and it is also possible to check further checking criteria which relate to a variable derived from the position of the ESV sheets, such as, for example, a spacing of the edges of the electrode sheets from one another along the deposition plane.The electrode sheets have an active region coated with an active material. In particular, the active regions of the electrode sheets are substantially rectangular. The electrode sheets themselves also have conductor tabs which can break this rectangular geometry.In the following, for reasons of improved readability, rectangular electrode sheets are nevertheless referred to, wherein this is to be understood with respect to the active regions or with respect to the electrode sheets without taking into account the conductor tabs.Without limitation of generality, a first edge of the electrode sheet extends along an x-direction after deposition and a second edge extends along a y-direction if the electrode sheet has been deposited correctly on the ESV.The x and y directions correspond in particular to an alignment of the workpiece carrier.In particular, the diverter tab is arranged on one of the second edges of the electrode sheet.The tolerance range of the ESV sheets assigned to the ESV sheets is essentially a range which has a predefined position and size with respect to the workpiece carrier. In particular, the tolerance ranges for the same type of ESV sheets are identical.According to one embodiment of the invention, it is provided that the separator sheets are contiguous along the y-direction and are integrally comprised in a separator strip, wherein the separator strip is alternately folded over at the second edges of the ESV and thus forms the separator sheets between the electrode sheets of the ESV.This embodiment allows the use of a continuous separator belt in which the separator sheets are ultimately integrally joined together.This embodiment may require that the first, second and / or third side views be taken from the sides of the first edge.Alternatively or additionally, the separator strip can also be semi-transparent, so that it is possible to see on the optical recordings, but electrode sheets lying behind them likewise remain visible.According to this embodiment, the separator strip ultimately stretches along a vertical axis of the ESV between the electrode sheets.A separator strip has the advantages, among other things, that fewer cuts are necessary and, on the other hand, an overlap of the electrode sheet is always ensured, at least along one edge.Alternatively, the separator sheets may also be present as individual, non-contiguous rectangular separator sheets that are stacked individually.According to a further embodiment of the invention, it is provided that the tolerance range assigned to the ESV sheet is determined on the basis of a limited deposition surface assigned to the respective type of ESV sheet, wherein the tolerance range assigned to the respective ESV sheet is spaced apart from the edges of the corresponding deposition surface by a predefined value, in particular symmetrically, in particular such that the tolerance range comprises at most 90%, in particular at most 80%, in particular at least 70%, of the corresponding part of the deposition surface.This provides a tolerance range which is slightly smaller than the maximum permissible deposition area for the ESV sheets. This makes it possible to reliably assume, on the basis of the optical tests, that an ESV whose test criteria after steps b) to d) continue to be satisfied is that the ESV has been manufactured in accordance with the specification.According to a further embodiment of the invention, it is provided that in step a) for each type of ESV sheet for each position which is determined for a selected region of the ESV sheet, an associated storage field is determined which is indicative of at least the determined positions, which differ furthest from one another, of the same selected region of the already stored ESV sheets of this type, and in particular all determined positions of the same selected regions of the already stored ESV sheets are detected, wherein the storage field is set in relation to the tolerance range, such that the check as to whether the positions determined in steps b) to d) are in the respective associated tolerance ranges is carried out relative to the storage field and the tolerance range set in relation thereto, wherein the check is positive, if the determined positions are within the tolerance range and negative if not.That is to say, to what extent the determined positions in steps b), c) and d) are still within the tolerance ranges is determined as a function of a relative position with respect to one another, so that no external marker or a reference coordinate system with respect to the workpiece carrier is required.Although, in particular with steps b) to d), the position of the respective ESV sheet cannot be completely determined, these steps are sufficient to be able to detect a change in the position of the ESV sheet after depositing all ESV sheets.According to a further embodiment of the invention, it is provided that if the determined positions are within the placement surface and outside the associated tolerance range, the ESV is subjected to a test by means of CT.That is to say, provided that the optical evaluation in steps b) to d) makes it possible for the ESV to be manufactured within the specifications, but only slightly, i.e. close to the permitted limits, this can be verified by means of a separate Ct test, so that the ESV can optionally be further processed.According to a further embodiment of the invention, before step a) and before depositing on the ESV, a geometry and, if appropriate, a position of the ESV sheet to be deposited is determined on the basis of an upstream optical recording, wherein, if the determined geometry of the ESV sheet lies in a component tolerance assigned to this variable, a correction vector is determined which is designed such that the ESV sheet is deposited centrally on the ESV by a depositing device on the basis of the determined geometry.This makes it possible to deposit each ESV sheet as centrally as possible, i.e. centrally along a common vertical axis of the ESV. That is, the correction vector is determined in particular with respect to the dimensions and the position of the ESV sheet, namely, so that the ESV sheet is ideally deposited centrally on the ESV.The component tolerance should in any case be within the tolerance range for the ESV. At most, the component tolerance may correspond to the tolerance range for the ESV blade.In particular, if the separator sheets are included in a separator tape, this embodiment can only be limited to the electrode sheets, or wherein the correction vector for the separator tape is determined only along the x-direction.According to a further embodiment of the invention, it is provided that if the determined geometry of the ESV sheet is not within the associated component tolerance and the ESV sheet is an electrode sheet or a single separator sheet, the ESV sheet is sorted out and is not deposited on the ESV stack.This embodiment advantageously makes it possible to determine, already before depositing an ESV sheet, whether the ESV sheet to be deposited is within a manufacturing tolerance. If this is not the case, a storage on the ESV could lead to an unsatisfaction of the predefined checking criteria, so that the ESV would have to be sorted out finally or would have to be subjected to delaying further checks.According to a further embodiment of the invention, it is provided that the predefined checking criteria of the ESV are completely determined on the basis of the determined positions in step a) of the ESV sheets.That is to say that if there were no risk of a subsequent change in position of the ESV sheets after the ESV sheet has been deposited, this information would be sufficient to achieve quality assurance in ESV production.However, since this is often not the case, the further test steps b) to d) are carried out according to the invention.According to a further embodiment of the invention, the ESV is sorted out of the production line and / or subjected to a computer tomography check if the determined position of the ESV sheet in step a) is not within the assigned tolerance range.This embodiment makes it possible to immediately detect a failed deposit of the ESV sheet on the ESV and to abort the process or to check it by a CT recording.If necessary, a correction vector for subsequent ESV sheet deposits can be determined from the missing deposit.According to a further embodiment of the invention, it is provided that the checking criteria are selected from the group consisting of:first test criterion: corner regions which form corners of the separator sheets must lie in a predefined deposition surface for separator sheets in the x and y directions;second test criterion: all outer corners of the anode sheets must lie in a predefined deposition surface for anode sheets in the x and y directions;Third test criterion: all outer corners of cathode sheets must lie in a predefined deposition surface for cathode sheets in the x and y directions;fourth test criterion: the sequence of the ESV sheets on the ESV must have an alternating sequence of anode and cathode sheets, between which a separator sheet is arranged in each case;fifth test criterion: a distance between the separator sheets and the anode sheets must be greater than a predefined minimum distance along the x and y directions;sixth test criterion: a distance between the cathode sheets and the anode sheets must be greater than a predefined minimum distance along the x and y directions;seventh test criterion: a position of the ESV sheets and the position of a workpiece carrier of the ESV have the same orientation and the ESV sheets are arranged centrally on the workpiece carrier.In particular, the predefined checking criteria comprise all checking criteria listed in this group. If not all ESV sheets are deposited on the ESV, the predefined checking criteria are checked with respect to the ESV sheets already deposited.With regard to the first test criterion, it should be noted in particular that, if the separator sheets are included in a separator strip, the corner regions are formed, for example, by the edges of the separator strip at which the separator strip bends from the placement plane along the vertical axis. In a photograph oriented to the storage plane, this edge can be identified unambiguously. These edges and the edges of the separator strip thus form corner regions for each separator sheet, on the basis of which corners of the respective separator sheet can be determined.According to a further embodiment of the invention, it is provided that the determined position of the separator sheets from step b) is used to check whether at least the first test criterion is also fulfilled after depositing all ESV sheets, and / or wherein the determined position of the anode sheets from step c) is used to check whether at least the second test criterion is also fulfilled after depositing all ESV sheets, and / or wherein the determined position of the outer contour line of the diverter tabs from step d) is used to check whether at least the second and third test criterion is also fulfilled after depositing all ESV sheets.According to a further embodiment of the invention, the ESV is fed to a further production step if compliance with the test criteria after storage has been verified by steps b) to d), in particular without a computer-tomographic checking of the test criteria being carried out.In particular, only if all the variables lie in the assigned tolerance ranges is there no computer-tomographic examination of the ESV with respect to at least some of the predefined test criteria.According to a further embodiment of the invention, it is provided that, if at least one variable correspondsthe determined position of the separator sheets,the determined position of the anode sheets, and / orthe determined position of the outer contour line of the arrester lugs is not in the respective assigned tolerance range, the ESV is subjected to a computer-tomographic checking of at least some or all of the predefined checking criteria before the ESV is either sorted out or fed to a further production step.This embodiment allows an ESV, which is likely not to meet all the test criteria on the basis of the results of the visual examination of the test criteria, to be examined in more detail with respect to the test criteria by means of a computer tomographic examination.According to a further embodiment of the invention, the ESV is moved along a vertical extension direction before depositing an ESV sheet in such a way that the deposition plane is always at the same height.According to a further aspect of the invention, an optical ESV test system is provided which is configured to carry out the method according to the first aspect of the invention, wherein the system has at least the following components:a computer,a depositing device which is configured to deposit the ESV sheets on a workpiece carrier and to be controlled by a control unit,a first optical recording system configured to record the ESV with view to the storage plane in order to produce the first and / or the fourth optical recording,a second optical recording system configured to record the ESV in a first side view in order to produce the second optical recording,a third optical recording system configured to record the ESV in a second and third side view in order to produce the third optical recording.According to a further aspect of the invention, there is provided a computer program comprising computer program code which, when executed on a computer, in particular when executed on the computer of the system, causes the computer to perform the method according to the invention.In the context of this specification, a computer program is also understood to mean, in particular, a computer program product, i.e., a computer program code stored on a non-transitory storage medium, which can be executed on a computer or at least one processor and, when executed, carries out the method according to the invention.The invention is explained below with reference to the exemplary embodiments shown in the attached drawings.They show FIG. 1 : Schematic illustration of deposition defects in the production of ESVs; FIG. 2 : schematic illustration of the deposition surfaces of an ESV; FIG. 3 : geometries of the ESV sheets; FIG. 4 : Changes in position of a type of ESV sheets between the method steps: FIG. 5 : Relation of different areas and surfaces for quality assurance: FIG. 6 : schematic representation of a first optical recording system; FIG. 7 : schematic representation of a second optical recording system; FIG. 8 : schematic representation of a third optical recording system; FIG. 9 : schematic representation of a fourth optical recording system.FIG. 1 shows an ESV 1 comprising a plurality of ESV sheets 10 stacked one on top of the other, which have a rectangular active region (with respect to a plane along an x-y perpendicular to the stacking direction z). The ESV 1 extends along a vertical axis which extends along a z-direction without restricting generality. The ESV sheets 10 extend along x and y directions.The ESV sheets 10 are selected from the group: electrode sheet, separator sheet 13, the group of electrode sheets comprising anode sheets 11 and cathode sheets 12, the ESV sheets being alternately stacked on top of each other; a separator sheet 13 and subsequently an electrode sheet 11, 12, the electrode sheets also being alternately deposited; an anode sheet 11 followed by a cathode sheet 12 with a separator sheet 13 therebetween. The active areas of the anode sheets 11 are circumferentially larger in the x-y plane than the active areas of the cathode sheets 12, and the separator sheets 13 are circumferentially larger in the x-y plane than the anode sheets. Each electrode sheet 11, 12 has a lead-off tab 11- 1, 12- 1 which, depending on the type of electrode sheet, are arranged on opposite sides of the ESV 1.The ESV sheets 10 are arranged on a workpiece carrier 2 which is part of the ESV 1. FIG. 1A shows an ideally stacked ESV 1 in which the ESV sheets 10 are all stacked exactly along the vertical axis h centrally one above the other. In comparison, a first type of depositing error can be seen in FIG. 1B, in which a successive translatory displacement along the x-direction takes place during depositing by a slight transverse force (indicated by the arrow K pointing obliquely toward the ESV), so that the ESV extends obliquely along the vertical axis, which is indicated by arrow 100. In FIG. 1C, a second type of placement error is shown. Here, immediately after deposition due to an acute transverse force K, a single ESV sheet 10, in the example an anode sheet 11, was deposited individually offset (arrow 101) with respect to the center μ of the ESV 1. The preceding ESV sheets 10 and also the following ESV sheets 10 are again deposited centrally on the ESV 1.In FIG. 1D, a third type of error is shown, in which a lateral jump (indicated by arrow 102) along the x-direction occurred and all ESV sheets 10 which were deposited subsequently are deposited displaced by this amount. The ESV 1 has a stage.FIG. 2 shows a section of the three storage surfaces 21, 22, 23 assigned to the respective types of ESV sheets. The ESV sheets 10 are intended to be arranged with their corners and edges in the assigned storage surfaces 21, 22, 23 in order to ensure a desired performance of the ESV 1. The cutout represents a fourth corner region (of four corner regions) of the ESV 1. The further corner regions are designed in an analogous manner (not shown).The deposition surface 23 for the separator sheets 13 extends furthest outward with respect to the center of the ESV 1. Along the x- and y-direction, this deposition surface 23 has an ideal nominal position SE4N(x), SE4N(y) for the separator sheets in the x- and y-direction. Extending symmetrically around these nominal positions is the deposition surface 23, which indicates a maximum deviation up to which a deposited separator sheet still lies within the desired production tolerance of the ESV, and thus within the deposition surface.The width Sd(x), Sd(y) of this deposition surface 21 around the respective nominal position SE 4N(x), SE 4N(y) is typically in the sub-millimeter range.Lying further inwards, the deposition surface 21 runs in an analogous manner, which represents the production tolerance with respect to the deposition of the anode sheets 11. Also shown is the deposition surface 22 relative to the cathode sheets 12. Both deposition surfaces 21, 22 have a nominal position for the respective electrode sheet and symmetrically circumferentially a range of maximum tolerated deviation. The widths - Ad(x) and Ad(y) or Kd(x) and Kd(y) - of these deposition surfaces 21, 22 are likewise in the sub-millimeter range.The deposition surfaces 21, 22, 23 are spaced apart from one another, wherein the deposition surfaces are selected such that a minimum distance dSR(x), dSR(y), dAK(x), dAK(y) or a minimum overlap is not undershot between the deposition surfaces; this minimum distance is also in the sub-millimeter range. All the relevant ESV sheets 10 must be deposited within the respective depositing surfaces 21, 22, 23 in order to produce the ESV 1 within the manufacturing tolerance.The names of the boundaries of the deposition surfaces are made here on the basis of the nomenclature explained below:X1-X2-X3(x / y)X1 denotes the deposition area for the respectively assigned type of ESV sheet. X1is selected from the lettersS for the deposition surface for the separator sheets,A for the deposition surface for the anode sheets,K for deposition surface for the cathode sheets.X2 denotes the respective corner of the deposition surface and thus also the corner of the respective ESV sheet. X2 is selected from the letter index combinations:E1 for the first corner,E2 for the second corner,E3 for the third corner,E4 for the fourth corner,In particular, the corner designation extends clockwise around the shelf / ESV sheet.X3 denotes the boundary or the nominal position of the respective deposition surface. X3 is selected from the lettersU for the outwardly extending boundary of the deposition surface;L for the inwardly extending boundary of the deposition surface;N for the nominal position for the respective ESV sheets - typically running centrally between U and L.(x / y) specifies the respective boundary or nominal position of the deposition surface with respect to the x or y direction and can assume the letters x for specifying the boundary or nominal position along the x direction or y for specifying the boundary or nominal position along the y direction.That is to say, for example, SE 4 L(x) denotes the inner boundary of the deposition surface assigned to the separator sheets along the x direction, see also FIG. 2.Likewise, distances may be specified with respect to these boundaries.FIGS. 3A to C each show schematically and by way of example which variables can be used to determine a geometry of the electrode sheets 11, 12 (FIGS. 3A+3B ) and of the separator sheets 13 (FIG. 3C ).To determine the geometry, the lengths l1, l2and the widths b1, b2of the edges of the respective ESV sheet 10 are determined, for example, optically and assigned to them, wherein apart from the diverter tabs 11- 1, 12- 1 of the electrode sheets 11, 12, a rectangular geometry is used as the basis. This rectangular geometry corresponds substantially to the active regions 11- 2, 12- 2 of the electrode sheets 11, 12.To determine the geometry, the corner positions E 1, E 2, E 3, E 4 of the ESV sheet 10 are determined on the basis of an optical recording.The distances l1, l2, b1, b2 between the determined corner positions E1, E2, E3, E4 are also determined in this step. The edges can also be designated ae1e2 for the edge of the anode sheet between the corners E1 and E2, ae2e3 for the edge of the anode sheet between the corners E2 and E3, ae3e4 for the edge of the anode sheet between the corners E3 and E4, ae4e1 for the edge of the anode sheet between the corners E4 and E1.Similarly, the edges of the electrode sheet may be designated ke1e2 for the edge of the cathode sheet between corners E1 and E2, ke2e3 for the edge of the cathode sheet between corners E2 and E3, ke3e4 for the edge of the cathode sheet between corners E3 and E4, ke4e1 for the edge of the cathode sheet between corners E4 and E1.However, the edges of the separator sheet may be denoted as se1e2 for the edge of the separator sheet between corners E1 and E2, se2e3 for the edge of the separator sheet between corners E2 and E3, se3e4 for the edge of the separator sheet between corners E3 and E4, se4e1 for the edge of the separator sheet between corners E4 and E1.The edges associated with the electrode sheets 11, 12 and the separator sheets are referred to by the enclosing corners and the ESV sheet type.Thus, ae2e3 denotes the edge of the anode sheet (a for anode) extending between the corners E2 and E3. Analogously, se1e2 denotes, for example, the edge of the separator sheet (s for separator) which extends between the corners E1 and E2.The edges extending between the corners E 1 and E 2 and between the corners E 3 and E 4 are the edges along the x direction. The edges extending between the corners E 4 and E 1 and between the corners E 2 and E 3 are the edges along the y-direction.Furthermore, the y-positions of the edge positions AF 1, AF 2, KF 1, KF 2 of the collector tabs of the anode and cathode sheets 11, 12 can be determined.For each ESV sheet 10, the four corners E1, E2, E3, E4 are determined. If a separator sheet 13 is involved, one or more x-positions M 1, M 2, M 3, M 4 of the edges of the separator sheet 13 and their distance from one another are additionally determined in the region of the conductor tabs of the electrode sheets.This determination of the geometry takes place before placement on the ESV 1.In particular, the determination of the x-position(s) of the edges of the separator sheet 13 turns out to be advantageous since these edges can be determined without doubt in the region of the diverter tab as soon as the separator sheet 13 has been deposited on an electrode sheet 11, 12. This is because an electrode sheet 11, 12 with the diverter tab 11- 1, 12- 1 situated under the separator sheet 13 covers all separator sheets 13 situated under this electrode sheet in the region of the diverter tab 11- 1, 12- 1, so that when the edges M 1, M 2, M 3, M 4 of the separator sheet are determined from an optical recording, the correct edge is reliably used as a basis and the edge of a separator sheet 13 arranged further down in the ESV is not incorrectly used.As soon as this edge position M 1, M 2, M 3, M 4 of the separator sheet in the ESV has been determined in the ESV 1, the position of the opposite edge and the position of the corners of the separator sheet can be deduced on the basis of the previously determined length of the separator sheet.The corners E 1, E 2, E 3, E 4 of the electrode sheets 11, 12 can be identified without doubt immediately after deposition on an underlying and peripherally protruding separator sheet 13. On the basis of some or all corner positions and the previously determined geometry of the respective electrode sheet 11, 12, it is possible to draw conclusions as to the position, i.e. in particular as to the orientation and the position in the ESV 1.Due to inevitably occurring length variations and variations in the position when picked up by a gripping unit of the depositing device of the ESV sheets 10 of the same type, a correction vector can be determined for each ESV sheet, which correction vector is designed such that the ESV sheet is deposited centrally on the ESV. If it is already found during the determination of the geometry that an ESV sheet is outside the production tolerance due to the geometry, this ESV sheet can be sorted out.The totality of the determined variables, i.e. the corner positions E 1, E 2, E 3, E 4 and, if appropriate, edge positions M 1, M 2, M 3, M 4, can be combined on the basis of an ESV sheet tolerance field for each type of ESV sheet. The ESV sheet tolerance field includes the length and shape variations of the ESV sheets based on manufacturing technology (see also FIG. 4A ).In contrast to the placement surface 21, 22, 23, which sets a maximum and minimum limit with respect to a lateral positioning of the ESV sheet 10 in the ESV, the ESV sheet tolerance field is formed from the determined measured values for the respective variable. That is to say that the tolerance field of all the determined measured values for the variable must lie completely within the placement surface 21, 22, 23 or, as far as the optical check is concerned, even within the tolerance range, so that the ESV is deemed to be manufactured in accordance with the permitted specification. The ESV sheet tolerance field captures the values of the size at least relative to each other.Immediately after depositing an ESV sheet on the ESV, and in particular before depositing a further ESV sheet, the corner positions E 1, E 2, E 3, E 4 and optionally certain edge positions M 1, M 2, M 3 M 4 of the ESV sheet and thus the position of the ESV sheet are determined (checking step a).Since the deposition never takes place 100% at the location at which the deposition is provided, a deposition field results which depends on the deposition accuracy. The storage area may be determined for each determined position (e.g., corner and edge positions) of the ESV sheet 10. This tray 51 must be fully within the tolerance range associated with the type of ESV sheet in order for the ESV to be considered to be within the specified manufacturing tolerance.This manufacturing tolerance is predefined on the basis of various test criteria.The tolerance range of the ESV sheet depends on the type of the ESV sheet; i.e. whether it is an anode, cathode or separator sheet (cf. FIG. 2 ).In FIG. 4, the above-described one is illustrated. FIG. 4A shows the measured corner positions of the anode sheets for two corners, E 1, E 2 of a common edge of the respective anode sheet 11, in the example positions of the first and the second corner of the anode sheets 11 before deposition on the ESV 1. The variation in length of the anode sheets 11 reflects the component tolerance in the form of the ESV sheet tolerance field 50. The totality of all determined corner positions (black and hatched points) in the tolerance field 50 assigned to this first edge defines the ESV sheet tolerance field 50 to the left and right of the anode sheets 11. For this reason, the ESV sheet tolerance fields 50 for the first and second corner positions E 1, E 2 are also symmetrical on the left and right.In an optical detection and testing step (testing step a), after deposition on the ESV 1 and in particular before deposition of a further ESV sheet, the positions of the corners E 1, E 2 and optionally selected edge positions of the anode sheet 11 just deposited are again determined. For this purpose, the corresponding positions of the deposited ESV sheet 10, here, for example, of the anode sheet 11, in a deposition plane are determined on the basis of a first optical recording of at least parts of the deposition plane of the ESV 1, i.e., for example, in plan view, obliquely or directly perpendicularly to the deposition plane of the ESV; see FIG. 4B.The deposition plane extends in particular along the x- and y-directions.The positions (black and hatched circles) thus determined are now checked with respect to predefined checking criteria, which includes the determination as to whether the deposited ESV sheet 10 lies in the tolerance range 52 of the tolerance range 52 assigned to this type of ESV sheet 10, but also as to whether the sequence of the ESV sheets, insofar as they have already been deposited, is correct.The recording of the ESV sheet size with subsequent recording of the ESV sheet layer in can be used for calculating the depositing accuracy of the production process.The difference between the position of the ESV sheet and the ESV sheet size can be used as a measure of the deposition accuracy. The size determined in this way can also be used, in particular, for the removal of the stacking process, which has to achieve a defined deposition accuracy.The known values additionally allow differentiation between a deposition accuracy of the process in a translatory x- and y-direction and in a rotatory direction.In addition, the storage field 51 is determined from the totality of all determined positions and, in particular, for each position determined in this context of characteristic regions, such as corners and specific edges, of the deposited ESV sheets for each type of ESV sheet; FIG. 4B.This deposition array 51 is schematically illustrated with respect to the location of a plurality of anode sheets for the corner positions along the first edge in FIG. 4B. In comparison with the ESV sheet tolerance field 50, some anode sheets 11 after deposition are shifted with respect to the corner positions (emphasized by hatching) and protrude from the ESV sheet tolerance field 50. This is illustrated in FIG. 4B.Similarly, these ESV sheet tolerance fields 50 and deposition fields 51 are also determined for the separator sheets, the cathode sheets and the corresponding sizes (not shown).In the case of ideal error-free deposition, the positions of the anode sheets 11 would again be at the same point in the deposition field 51 as in the ESV sheet tolerance field 50. Due to deposition inaccuracies, it usually occurs that the anode sheet 11 (despite the correction vector) is deposited slightly offset with respect to the center of the workpiece carrier and thus optionally protrudes from the ESV sheet tolerance field 50. By the plurality of corner positions thus detected with respect to an ESV center, the tray array 51, which is usually larger than the ESV sheet tolerance array 50, is defined.In addition to the determination of the deposition fields 51 for each type of ESV sheets 10, it is checked for each deposited anode sheet 10 (and likewise also for the other types of ESV sheets) whether the positions of the respective ESV sheet 10 are within the tolerance range 52 assigned to the type of ESV sheet 10. If the position is not in the tolerance range 52, the production of the ESV can be interrupted.Ideally, the determined deposition field 51 lies completely within the tolerance range 52, so that a difference range 53 (see FIG. 5A ) between the deposition field 51 and the tolerance range 21, 22, 23 for which the respective determined position can be determined.A change in the position of individual or multiple ESV sheets that has occurred after all ESV sheets 10 have been deposited is reflected in a subsequent check-checking steps b) to d) in particular in that the position of the size (e.g. the corner position(s) of one or multiple corners of the deposited ESV sheet or an edge position) in the respective deposition field 51 is changed at least relative to the determined positions of the other ESV sheets (of the same type) or a medium nominal position in the deposition field during at least one of these subsequent checks (see FIG. 4C ).If such a change is present, it can be checked to what extent the deviating position still falls within the difference range 53.If the checked position is also not in this difference range 53, then this variable is no longer in the tolerance range 52 assigned to it.Whether an ESV sheet 1 has slipped after depositing the last ESV sheet on the ESV in comparison to the position determined immediately after depositing is determined on the basis of a plurality of optical recordings which are each made from different directions on the ESV.To this end, it is to be noted that a subsequent change in position of the ESV sheets 10 is determined, in particular in reference to the determined deposition field 51. This makes it possible to check, independently of the coordinate system, whether all ESV sheets 10 are located at the expected location and whether a deviation has occurred with respect to the positions in the storage area 51. That is to say that for each ESV sheet 10, the corresponding measurement variable is determined with respect to the deposition field 51.Especially because the determination of the positions of the ESV sheets 10 takes place after all the ESV sheets 10 have been deposited on the ESV 1, in particular by recording different side views, it is advantageous to use the depositing fields 51 as a reference (in contrast to a workpiece carrier-related coordinate system), since here in particular a relative positioning of the ESV sheets is checked, so that a referencing to an external or workpiece carrier-related coordinate system can be omitted.FIGS. 5A and 5B schematically show the relationship between the storage area 51 and the associated tolerance range 52.In Fig. 5A, the deposition array 51 for the position of a corner for the separator sheets is shown. The deposition field 51 lies on the inside and extends by a nominal value for the separator corner positions determined in test step a) for the second corner of the separator sheets.The corner positions were determined within the scope of the determination of the position of the separator sheets immediately after depositing each separator sheet in test step a) and combined to form the deposition field 51.The tolerance range is determined in relation to the predefined deposition surface 23 for the separator sheets. The separator sheet depositing surface 23 extends outwardmost in Fig. 5A.For example, the tolerance range 52 can be defined such that it has a minimum distance to the boundaries of the placement surface 23. This distance may be given as a percentage or in absolute units. The extent to which the distance from the boundaries is intended can be determined on the basis of the plant characteristic, on the basis of a subsequent evaluation of data from previously produced ESV stacks, or similar statistical considerations.The comparison of the deposition field 51 with the associated tolerance range 52 for the corner positions of the separator sheets 13 makes

Claims

Method for testing test criteria of an electrode-separator composite (1) (ESV) with ESV sheets (10) comprising the following types of ESV sheets (10), separator sheets (13) and electrode sheets (11, 12), the latter selected from the group comprising anode sheets (11) and cathode sheets (12), comprising the following steps: a) After depositing an ESV sheet (10) on the ESV (1), a plurality of positions of selected regions of the deposited ESV sheet (10) are determined, wherein at least the positions which are determined again in the following steps b) to d) are comprised in the plurality of positions, wherein the positions in a placement plane (400) of the ESV sheet are determined on the basis of a first optical recording in plan view; b) after placement of all ESV sheets (10) on the ESV (1), a position of the separator sheets (13) along an x-direction (x) along which a first edge of the ESV (1) extends is determined on the basis of a second optical recording of a first side view of the ESV (1); c) after placement of all ESV sheets (10) on the ESV (1), a position of the anode sheets (11) along the x-direction (x) and a y-direction (y) of the ESV (1) is determined, wherein a second edge of the ESV (1) extends along the y-direction (y), on the basis of a third optical recording comprising a second and third side view of the ESV (1), d) After depositing all ESV sheets (10) on the ESV (1), a position of an outer contour line (11-3, 12-3) of diverting tabs (11-1, 12-1) of the electrode sheets (11, 12) is determined, wherein the position with respect to the y direction is determined on the basis of a fourth optical recording of the ESV 1 in plan view of the ESV (21), wherein in step a) it is checked for each ESV sheet (10) whether the ESV sheet (10) lies in a tolerance range (52) assigned to the type of the ESV sheet (10), wherein in steps b) to d) it is checked, whether the ESV (1) meets at least some predefined test criteria even after depositing all ESV sheets (10), wherein this test is positive if all determined positions in steps b) to d) continue to lie in the associated tolerance range (52), and negative if not all determined positions lie within the associated tolerance range (52).The method according to claim 1, characterized in that the separator sheets (13) are contiguous along the y-direction (y) and are comprised in a separator tape, wherein the separator tape is alternately folded at the second edges of the ESV (1) and thus forms the separator sheets between the electrode sheets (11, 12) of the ESV (1).The method according to claim 1 or 2, characterized in that the tolerance range (52) assigned to the ESV sheet (10) is determined on the basis of a limited deposition surface (21, 22, 23) assigned to the type of the respective ESV sheet (10), wherein the tolerance range (52) assigned to the respective ESV sheet (10) is spaced apart from the edges of the corresponding deposition surface (21, 22, 23) by a predefined value, in particular such that the tolerance range comprises at most 90%, in particular at most 80%, in particular at least 70%, of the corresponding part of the deposition surface (21, 22, 23).The method according to claim 3, characterized in that in step a) for each type of ESV sheet (10) for each position determined for a selected area of the ESV sheet (10) an associated deposit field (51) is determined which is indicative of at least the determined positions most deviating from each other, of the same selected area of the already deposited ESV sheets (10) of this type, wherein the deposit field (51) is set in relation to the tolerance range (52), so that the check as to whether the positions determined in steps b) to d) are in the respective associated tolerance ranges (52) is carried out relative to the deposit field (51) and the tolerance range (52) set in relation thereto, wherein the check is positive, if the positions determined are within the tolerance range (52) and negative if not.The method according to one of the preceding claims, characterized in that before step a) and before depositing on the ESV (1), a geometry of the ESV sheet (10) to be deposited is determined on the basis of an upstream optical recording, wherein, if the determined geometry of the ESV sheet (10) lies in a component tolerance assigned to this variable, a correction vector is determined which is designed such that the ESV sheet is deposited centrally on the ESV (1) by a depositing device on the basis of the determined geometry.The method according to claim 5, wherein if the determined geometry of the ESV sheet (10) is not within the associated component tolerance and the ESV sheet (10) is an electrode sheet (11, 12) or a single separator sheet (13), the ESV sheet (10) is sorted out and is not deposited on the ESV (1).The method according to any one of the preceding claims, characterized in that the predefined checking criteria of the ESV (1) are completely determined on the basis of the determined positions of the selected areas of the ESV sheets (10).The method according to any one of the preceding claims, characterized in that if the determined positions of the selected areas of the ESV sheet (10) in step a) are not in the associated tolerance range (52) for the ESV sheet (10), the ESV (1) is sorted out from a production line.The method according to any one of the preceding claims, wherein the test criteria are selected from the group consisting of: - First test criterion: corner regions forming corners of the separator sheets (13) must lie in a predefined deposition surface (23) for separator sheets (13) in the x and y directions; - Second test criterion: All outer corners of the anode sheets (11) must lie in a predefined deposition surface (21) for anode sheets (11) in the x and y directions; - Third test criterion: All outer corners of cathode sheets (12) must lie in a predefined deposition surface (22) for cathode sheets (12) in the x and y directions; Fourth test criterion: the sequence of the ESV sheets (10) on the ESV must have an alternating sequence of anode and cathode sheets (11, 12) between which a separator sheet (13) is arranged in each case; Fifth test criterion: a distance between the separator sheets (13) and the anode sheets (12) along the x and y directions must be greater than a predefined minimum distance; Sixth test criterion: a distance between the cathode sheets (12) and the anode sheets (11) along the x and y directions must be greater than a predefined minimum distance; seventh test criterion: a position of the ESV sheets (1) and the position of a workpiece carrier (2) of the ESV (1) have the same orientation and the ESV sheets (10) are arranged centrally on the workpiece carrier (2).The method according to claim 9, characterized in that the determined position of the separator sheets (13) from step b) is used to check whether at least the first check criterion is also fulfilled after depositing all ESV sheets (10), and / or wherein the determined position of the anode sheets (11) from step c) is used to check whether at least the second check criterion is also fulfilled after depositing all ESV sheets (10), and / or wherein the determined position of the outer contour line (11-3, 12-3) of the diverter tabs (11-1, 12-2) from step d) is used to check whether at least the second and third check criterion is also fulfilled after depositing all ESV sheets (10).An optical ESV inspection system comprising at least the following components: - a computer comprising a computer program with computer program code, - a depositing device configured to deposit the ESV sheets (10) on a workpiece carrier (2) and to be controlled by a control unit, - a first optical recording system (301) configured to record the ESV (1) with view to the depositing plane (400) in order to produce the first and / or the fourth optical recording, - a second optical recording system (302) configured to record the ESV (1) in a first side view in order to produce the second optical recording, - a third optical recording system (303) configured to record the ESV (1) in a second and third side view, To create the third optical record, characterised in that the computer program code, when executed on the computer, causes the ESV test system to perform the method according to any one of the preceding claims.A computer program comprising computer program code which, when executed on a computer, causes the system of claim 11 to carry out the method of any one of claims 1 to 10.

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