Method for manufacturing an electrode

Abstract

The invention relates to a method for manufacturing an electrode from an electrode continuous web (9), comprising a coating process in which the electrode continuous web (9) is coated with an electrode coating (5), and a cutting process in which a coating-free region (11) is cut to size, more particularly thereby forming arrester lugs (7). The method has a marking process in which the coating-free region (11) of the electrode continuous web (9) is marked for production tracking in the case of a proof of origin or a quality complaint. According to the invention, the marking process is an embossing process in which a continuous embossing pattern (19), which is gap-free in the direction of manufacture (F) and varies, is embossed as a marking into the coating-free region (11) of the electrode continuous web (9).

Description

[0001] Description Method for producing an electrode The invention relates to a method for producing an electrode according to the preamble of claim 1 and to a process arrangement according to claim 10. In an electrode / separator stack of a battery cell, electrode sheets (i.e. anode sheets and cathode sheets) are stacked one on top of the other alternately with separator sheets. The respective electrode sheet has a current collector which is formed from an aluminum foil or a copper foil. The current collector is usually coated on both sides with an electrode coating. In addition, the current collector has a laterally projecting, coating-free collector tab. Such an electrode sheet is produced in a generic battery cell production as follows: Accordingly, a foil-like continuous electrode web is first provided.This is subjected to a coating process in which the continuous electrode web is coated with the electrode coating. This is followed by a cutting process in which a coating-free area of ​​the continuous electrode web is cut to form conductor tabs. The process then continues with singulation, in which the coated and cut continuous electrode web is separated into electrode sheets. Battery cell production involves processing web material. This consists of aluminum and copper foil, which are coated to form electrode rolls several thousand meters long. The coating takes place in two passes: first the top side of the web is coated, followed by the underside. In the further course of production, electrode sheets are cut from the web and battery cells are built.For product traceability in the event of proof of origin or a quality complaint ("Track & Trace"), it is advantageous if the individual electrode sheets in a battery cell can be identified and assigned to an electrode roll with documented materials and production parameters. According to a first known solution, after coating, a colored spray mark is printed on the web with an inkjet printer in the uncoated area of ​​the film during the ongoing process. This mark is printed at regular intervals (e.g., every meter) or only in the event of anomalies (defect marking). The mark is detected by sensors in subsequent production steps. According to a second known solution, after coating, a mark is burned onto the web with a laser in the uncoated area of ​​the film during the ongoing process. This mark is printed at regular intervals (e.g.,every meter) or only in the event of abnormalities (defect marking). The marking is detected by sensors in subsequent production steps. According to a third known solution, an adhesive marker (e.g. label) is affixed to the web after coating in the uncoated area of ​​the film during the ongoing process, specifically in the event of abnormalities (defect marking). The marking is detected by sensors in subsequent production steps. All three prior art solutions have in common that the marking is only applied after the second coating pass. This means that production can only be traced back to after the second coating pass. Information about the first coating pass and the film is therefore lost. Markings cannot be applied beforehand because the uncoated areas on which marking can be applied only become visible after coating.A further disadvantage is that the marking on the web is done at intervals and not seamlessly. If, for example, every new meter is marked, many individual sheets within a meter will remain unmarked. Reducing the intervals to ensure each individual sheet has a mark is not possible because it is not clear at the time of marking where the individual sheet will be cut out. There are also specific disadvantages: With the inkjet printer solution, the spray marking takes time to dry and can become smudged and unreadable during further processing. The ink is a foreign substance that must not come into contact with the electrode coating to avoid triggering a negative chemical reaction in the battery cell, nor must it remain on the uncoated area of ​​the film because this is where the individual sheets are welded together and the weld seam is weakened by foreign substances.Inkjet printers are maintenance-intensive, can clog, and print heads must be cleaned regularly. Furthermore, ink consumption results in high operating costs and low reliability, as, for example, an empty ink tank or clogged lines lead to incorrect or missing markings. Laser solutions require significant operating expenditure due to occupational health and safety requirements associated with lasers. Furthermore, uncontrolled emission of metallic particles occurs due to material removal from the film, which can remain on the electrode coating and cause short circuits in the battery cell. Furthermore, system costs are high due to the laser source and extraction system, as well as high energy costs due to the laser source. Furthermore, laser solutions are sensitive to changes in production parameters (e.g., web speed) because the heat input required to burn in the marking changes depending on whether the web is moving slowly or quickly.When using an adhesive marker, e.g. labels, (third solution), these cannot be incorporated into a battery cell but must be removed again. Markers with poor adhesion can fall off during further processing. Markers protruding from the electrode roll can be bent or torn off during further processing. In addition, high operating costs arise due to the consumption of labels and low reliability, since, for example, an empty label roll leads to missing markings. US 2012 / 0295145 A1 discloses an electrode arrangement for a battery cell. WO 2013 / 018254 A1 discloses a method for producing an electrode sheet. The object of the invention is to provide a method and a process arrangement by means of which reliable product traceability is possible compared to the prior art. This object is achieved by the features of claim 1 or claim 10.Preferred developments are disclosed in the subclaims. The invention is based on a manufacturing method in which a continuous electrode web is coated with an electrode coating in a coating process. This is followed by a cutting process in which a coating-free area of ​​the continuous electrode web is cut to size, in particular to form conductor tabs. The method also comprises a marking process in which the coating-free area of ​​the continuous electrode web is marked. The marking allows product traceability, specifically in the event of proof of origin or a quality complaint. According to the characterizing part of claim 1, the marking process is implemented as an embossing process.In the embossing process, before the cutting process, and in particular before the coating process, a continuous, gapless, varying embossed pattern in the production direction is embossed as a marking into the coating-free area of ​​the endless electrode web. According to the invention, an uncoated aluminum or copper foil is provided with a gapless marking without foreign matter. The gapless marking is continuously embossed into the foil using embossing rollers. The formed structure has a depth of less than one μm and does not affect the mechanical stability of the foils, which can be up to 4 μm thick. The marking, which varies in the longitudinal direction of the web, is produced by combining different patterns on embossing rollers with different diameters on the top and bottom sides of the web. The arrangement and diameter of the embossing rollers are designed so that the combination is only repeated after a complete electrode roll (e.g., after 10,000 m).The embossing rollers are coupled to rotary encoders that detect the position of the embossing rollers with the current position of the web. The marking can be derived from the positions of the embossing rollers and thus the position of the web can be deduced. Sensors, e.g. a camera, can decipher the marking. The core of the invention is that the marking is done without foreign substances (e.g. ink, labels), but rather by embossing. Furthermore, the marking is seamless, i.e. continuous. Furthermore, the marking varies along the longitudinal direction of the web through the combination of geometric patterns on the top and bottom sides of the film. For example, several embossing rollers with different diameters can be in embossing engagement, arranged above and below the web, with different patterns and in several tracks. The web moves through the embossing rollers. The embossing rollers are connected to rotary encoders that detect the current rotational position of the embossing rollers.In addition, the current position of the web is detected via a deflection roller connected to a rotary encoder. Rotary encoders send signals to a controller, which assigns the current embossing roller positions to the current web position and saves them. In the following production steps, a camera records the embossed patterns on the web. The camera is connected to a controller in which the possible pattern combinations are stored. The position of the embossing rollers and, from this, the current web position are deduced from the detected pattern. Key aspects of the invention are highlighted again in detail below: For example, in a technical implementation for product traceability, a database, an optical sensor, and a comparator module are provided. The embossing pattern, which varies in the longitudinal direction of the web, or parameters correlating with it, are stored in the database as a function of the longitudinal position of the web.With the help of the optical sensor, the embossed pattern embossed into the endless electrode web can be optically captured in an image at a later time in the process. The comparator module can compare the optically captured image with sections of the embossed pattern stored in the database. If there is a match, the longitudinal web position of the embossed pattern section is assigned to the optically captured image, thus enabling product traceability. The embossing tool used in the embossing process can preferably be a roller unit with at least one embossing roller. During the embossing process, the embossing roller rolls on the coating-free area of ​​the endless electrode web. The embossing roller has an embossing contour on its outer circumference, which is embossed into the coating-free area of ​​the endless electrode web during the embossing process, forming the embossed pattern.Reducing the computing effort and the equipment required for recording and storing the embossing pattern in the database is of great importance. For this reason, reading image data of the embossing pattern into the database can be avoided, as this would require a lot of memory. Instead, parameters correlating to the embossing pattern can be read into the database, such as the rotational positions of at least one embossing roller that correlate with the embossing pattern. For this purpose, the embossing roller has a rotary encoder that is in signal connection with a control unit that controls the embossing roller. The rotational position of the embossing roller correlates with the current longitudinal web position at which the current embossing process is taking place. In addition, the rotational position of the embossing roller correlates with the embossing pattern section currently produced in the embossing process.Therefore, a correlating embossing pattern section can be easily derived from the rotational position of the embossing roller. Against this background, the rotational positions of the embossing roller can be stored in the database as correlating parameters instead of the embossing pattern. It is preferred if the roller unit has at least one embossing roller pair, through whose roller gap the coating-free region of the endless electrode web is guided. It is particularly advantageous if the roller unit has several embossing roller pairs arranged one behind the other in series. An exemplary embodiment of the invention is described below with reference to the attached figures. There show: Figs. 1 to 8 each show different views illustrating the manufacturing method according to the invention.Figure 1 shows an electrode sheet 1 produced using a method according to the invention, which is a component of an electrode / separator stack (not shown) of a battery cell. The electrode sheet 1 is formed with a central current collector foil 3 (for example, aluminum foil or copper foil) coated on both sides with an electrode coating 5. The current collector foil 3 is extended laterally outwardly with a coating-free collector tab 7. The electrode sheet 1 is produced from a still uncoated base foil web 10 (Figure 2). In the uncoated state, this is first passed through a marking station M (Figure 2) described later. The base foil web 10 is then divided along the longitudinal cutting lines 15 (shown in Figure 2) into a total of four continuous electrode webs 9.The endless electrode webs 9 are subjected to a coating process in which each endless electrode web 9 is coated on its top and bottom sides with the electrode coating 5. Alternatively, the base film web 10 can also be subjected to the coating process. After passing through the marking station M, the base film web 10 is transferred to the next process station via a deflection roller 13 in Figure 2. Figure 5 shows a web section of an already coated endless electrode web 9. Accordingly, the endless electrode web 9 has a coating-free region 11 on its right-hand longitudinal edge side extending in the production direction F, in which, for example, a three-track embossed pattern 19 is embossed. The endless electrode web 9 thus provided is subjected to a cutting process.During the cutting process, the endless electrode web 9 is cut along the dashed cutting lines 36 (Figure 5). In the process, the conductor lugs 7 are punched out in the coating-free area 11 of the endless electrode web 9. In addition, the electrode sheets 1 are separated from the endless electrode web 9. In the marking station M indicated in Figures 2 and 3, the areas 11 (Figure 5) of the base film web 10 that remain coating-free after the electrode coating are marked with an embossed pattern 19 in an embossing process. The marking can be done on one or both sides. The embossed pattern 19 enables product traceability in the event of proof of origin or a quality complaint about the manufactured electrode sheets 1. According to the invention, the marking, i.e. the embossed pattern, is carried out without foreign substances, so that the chemical reactions of a battery cell are not negatively influenced.Welding can also be carried out directly at the marked location, without the weld seam being weakened by foreign substances. The coating can also be applied directly to the marking without any negative interactions. In the illustrated embodiment, the embossed pattern 19 is embossed into the coating-free areas 11 (Figure 5) by means of a roller unit 17 (Figure 2). The embossed pattern 19 extends continuously and seamlessly in each of the coating-free areas 11 (Figure 5) in the production direction F. In addition, the embossed pattern 19 varies along the production direction F. In Figure 2, the roller unit 17 consists of a total of four embossing roller pairs 21, 22, 23, 24 arranged one behind the other in the production direction F. In Figure 3, the roller unit 17 has, by way of example, only three roller pairs 22, 24, 26.Embossing contours 30 are formed on the outer circumference of each of the embossing rollers, which emboss the embossed pattern 19 into the coating-free areas 11 during the embossing process. In Figure 2, the embossing roller pairs 21 to 24 and the deflection roller 13 each have a rotary encoder 20, which is in signal connection with an electronic control unit 25, by means of which the embossing rollers can be controlled. The rotary encoders 20 are used to detect the rotational positions D1(x) to D4(x) of the embossing rollers. The rotational positions D1(x) to D4(x) of the embossing rollers correlate with the current longitudinal web position x, at which the current embossing process is taking place. The longitudinal web position x is detected using the rotary encoder 20 of the deflection roller 13. In addition, the rotational positions D1(x) to D4(x) of the embossing rollers correlate with the embossed pattern section A(x) currently embossed in the embossing process (Figure 8).Therefore, for each longitudinal web position x, a correlating embossed pattern section A(x) can be derived from the rotational positions D1(x) to D4(x) of the roller pairs 21 to 24. To carry out product tracking, a database 27, an optical sensor 29, and a comparator module 31 are provided as shown in Figure 2. The electronic control unit 25 reads the embossed pattern 19, which varies in the longitudinal web direction, and / or the corresponding rotational positions D1(x) to D4(x) of the roller pairs 21 to 24 into the database 27 as a function of the respective longitudinal web position x and stores them there in a table, as indicated in Figure 7. In Figure 7, the longitudinal web positions x1 to x5, the embossing pattern 19 as a function of the longitudinal web positions x1 to x5, as well as the corresponding rotational positions D1(x) to D4(x) of the roller pairs 21 to 24 are shown in a table as examples.For the electrode sheet 11 shown in Figure 1, product tracking is carried out as an example. For this purpose, the conductor lug 7 of the electrode sheet 11 is optically captured as an image B with the aid of the optical sensor 29. The image B is sent to the comparator module 31. In addition, the data x, D1(x) to D4(x) stored in the database 27 and / or the embossed pattern 19 are read into the comparator module 31. As can be seen from Figure 8, in the comparator module 31, the image B is compared with sections A(x) of the embossed pattern 19 stored in the database 27 (or with the correlating parameters D1(x), D2(x), D3(x), D4(x)). In Figure 8, for example, the image B corresponds to the embossed pattern section A(x4). Due to the correspondence of the captured image B with an embossed pattern section A(x4), the web longitudinal position x4 is assigned to the optically captured image B.In this way, the longitudinal web position of image B is identified, which is required for product traceability. In the database 27 shown in Figure 7, both the embossing pattern 19 and the rotational positions D1(x) to D4(x) of the embossing roller pairs 21 to 24 are stored as parameters that correlate with the embossing pattern 19. In the exemplary embodiment shown, the embossing pattern has three tracks, each track consisting of spaced-apart bars running in the longitudinal direction. Alternatively, the embossing pattern 19 can also be implemented in any other way. Furthermore, the number of tracks can be selected arbitrarily. The marking station M can, for example, be integrated into the coating system. Alternatively, the marking station M can be integrated into the film production or implemented as a separate system. The optical sensor 29 can, for example, be a line scan camera or be implemented by contrast sensors.

[0002] List of reference symbols 1 Electrode sheet 3 Current collector foil 5 Electrode coating 7 Collector lug 9 Continuous electrode web 10 Base foil web 11 Coating-free area 13 Deflection roller 15 Longitudinal sections 17 Roller unit 19 Embossing pattern 20 Rotary encoder 21 to 24 Embossing roller pairs 25 Electronic control unit 27 Database 29 Optical sensor 30 Embossing contour 31 Comparator module 36 Cutting lines x Longitudinal web position D1(x), D2(x), D3(x), D4(x) Rotational positions of the embossing rollers B Image F Production direction A(x) Embossing pattern section M Marking station

Claims

1. A method for producing an electrode from a continuous electrode web (9), comprising - a coating process in which the continuous electrode web (9) is coated with an electrode coating (5), - a cutting process in which a coating-free region (11) is cut to size, in particular to form conductor lugs (7), wherein the method comprises a marking process in which the coating-free region (11) of the continuous electrode web (9) is marked for product traceability in the event of proof of origin or a quality complaint, characterized in that the marking process is an embossing process in which a continuous embossed pattern (19) which is continuous in the production direction (F) and varies is embossed as a marking in the coating-free region (11) of the continuous electrode web (9).Method according to claim 1, characterized in that the marking process takes place before the cutting process, in particular before the coating process.

3. Method according to claim 1 or 2, characterized in that the following is provided for product traceability: - a database (27) in which the embossed pattern (19) varying in the longitudinal direction of the web or parameters correlating therewith (D1(x), D2(x), D3(x), D4(x)) are stored as a function of the longitudinal position (x) of the web; - an optical sensor (29) which, at a later time in the process, optically captures a section of the embossed pattern (19) in an image; and - a comparator module (31) that compares the optically captured image (B) with sections (A(x)) of the embossed pattern (19) stored in the database (27), and that, if there is a match, the longitudinal path position (x) of the embossed pattern section (A(x)) is assigned to the optically captured image (B). 4.Method according to claim 1, 2 or 3, characterized in that the embossing tool used in the embossing process is a roller unit (17) with at least one embossing roller (21 to 24) which rolls on the coating-free area (5) of the endless electrode web (9), and in particular that the embossing roller (21 to 24) is on. The outer circumference has an embossed contour (30) which is embossed into the coating-free region (11) of the endless electrode web (9) during the embossing process, forming the embossed pattern (19).

5. The method according to claim 4, characterized in that the embossing roller (21 to 24) has a rotary encoder (20) which is in signal connection with a control unit (25) that controls the embossing roller (21 to 24).

6. The method according to claim 5, characterized in that the rotational position of the embossing roller (21 to 24) correlates with the current web longitudinal position (x) in which the current embossing process takes place, and / or that the rotational position (D1(x), D2(x), D3(x), D4(x)) of the embossing roller (21 to 24) correlates with the embossed pattern section (A(x)) currently embossed in the embossing process, so that a correlating embossed pattern section (Ax)) can be derived from the rotational position (D1(x), D2(x), D3(x), D4(x)) of the embossing roller (21 to 24).Method according to claim 6, characterized in that in addition to the embossing pattern (19) or instead of the embossing pattern (19), the rotational position (D1(x), D2(x), D3(x), D4(x)) of the embossing roller (21 to 24) is stored in the database (27) as correlating parameters.

8. Method according to claim 5, 6 or 7, characterized in that the roller unit (17) has at least one, in particular several, embossing roller pairs (21 to 24) arranged one behind the other in series, and in that the coating-free region (11) of the endless electrode web (9) is guided through the nip of the embossing roller pair (21 to 24).

9. Method according to one of the preceding claims, characterized in that after the cutting process, a singulation process takes place in which the coated endless electrode web (9) is singulated into electrode sheets (1).

10. Process arrangement for carrying out a method according to one of the preceding claims.

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