WO2024008720A1

WO2024008720A1 - Measurement system and method for measuring a coated electrode

Info

Publication number: WO2024008720A1
Application number: PCT/EP2023/068401
Authority: WO
Inventors: Masahiro Nomura
Original assignee: Northvolt Ab
Priority date: 2022-07-06
Filing date: 2023-07-04
Publication date: 2024-01-11

Abstract

A measurement system (10) adapted to arranged in connection with a roll-to-roll process, wherein in the roll-to-roll process a foil material (2) is provided with at least one layer of a coating material (3) and is arranged to be transported along a foil pathway (4), and wherein said measurement system (10) comprises: at least two sensors (1, 1') arranged at fixed positions across a width (W1) of said foil material (2); and wherein said sensors (1, 1') are adapted to detect at least one edge portion (E2) of said coating material and at least one edge portion (E1) of said foil respectively.

Description

MEASUREMENT SYSTEM AND METHOD FOR MEASURING A COATED ELECTRODE TECHNICAL FIELD The present disclosure generally pertains to a measurement system and a method for measuring so called coated electrodes, in particular coated electrodes for an electrode roll and cylindrical secondary battery cells. BACKGROUND In addressing climate change, there is an increasing demand for rechargeable batteries, e.g. to enable electrification of transportation and to supplement renewable energy. Such batteries typically comprise a number of cells, often referred to as secondary cells. In battery manufacturing it is known in the art to provide an electrically conductive sheet with a coating that is rolled up into a cylinder. In so called tabless cells, the electrically conductive sheet has an uncoated edge protruding on a side of the cylinder. The edge may be folded to provide an electrical contact surface. During coating a slurry comprising material for either the anode or cathode is extruded onto a foil, such as a copper or aluminium foil. Before the foil enters into a drying chamber or oven, the coating goes through quality control, including checking the thickness and spread, i.e. the width across the foil, to make sure that the coating is even and has the correct dimensions. Conventionally, measurement of the width is performed on the wet side of the drying chamber and by a series of, or array of, cameras. The equipment is quite expensive and even more, with increasing widths of the coated electrode, up to 1500 mm, requires more cameras to be installed in order to perform the measurement. As the demand for rechargeable batteries increases, more and more focus is being placed on production speed and accuracy; there is also a need to increase the speed and accuracy without increasing the cost. SUMMARY It is in view of the above considerations and others that the embodiments of the present invention have been made. The present disclosure aims at providing a measurement system and method of measurement which is efficient and less costly in the manufacturing process of coated electrodes. According to a first aspect, the present disclosure provides a measurement system adapted to arranged in connection with a roll-to-roll process, wherein in the roll-to-roll process a foil material is provided with at least one layer of a coating material and is arranged to be transported along a foil pathway, and wherein said measurement system comprises: at least two sensors arranged at fixed positions across a width of said foil material (or foil pathway); and wherein said sensors are adapted to detect at least one edge portion of said coating material and at least one edge portion of said foil respectively. By detecting the edge or edge portion is meant that the sensor is able to differentiate between the coating and substrate of foil. Since the system is adapted to detect the edge of the coating and the substrate or foil it is possible to calculate the width of the coating material based on the positioning of the sensors and the speed that the foil or substrate travels along the pathway. Since only the edge or edge portion need to be detected, i.e. a smaller portion of the coating layer, the need for a full array of, e.g. cameras, is not necessary and hence the cost of the measurement system can be reduced. By detecting the edge or edge portion, also the resolution of the measurement can be greatly increased without added cost, since smaller detectors, being of lower cost than larger detectors, could be utilized. The sensors may be arranged in line with each other or arranged off-set at said fixed positions. In some embodiments, the at least two sensors (1, 1’) are physically joined by an object that fixates the distance between the sensors. In some embodiments, the object that fixates the distance between the sensors comprises, or are essentially composed of, a material with a coefficient of thermal expansion of below 5 ppm/˚C, preferably below 3 ppm/ ˚C, more preferably below 2 ppm/ ˚C, as measured using interferometry. The distance between the sensors may be used for determining and/or controlling the width of the electrode. By having an object, such as a rod/bar/scaffold or similar between the sensors, thereby controlling and/or being aware of the exact distance between the sensors, one will also know the exact width of the electrode. Preferably, this object (rod/bar/scaffold) is comprising, or is essentially composed of, a material with low thermal expansion, such as a metal, alloy, glass, or ceramic material, to control this distance. Examples of such materials are iron-nickel alloys, and in particular the alloy FeNi36 (1.2 ppm/^oC) comprising about 64 wt% Fe and about 36 wt% Ni, fused quartz (0.59 ppm/^oC), or carbon fiber reinforced polymers, along the fiber direction (- 0.5-0.7 ppm/^oC), Sitall CO-115M (0.15 ppm/^oC). It may be noted that 1ppm/^oC corresponds to 1 µm of change in measured value when temperature changes by 1 ^oC when each sensor to sensor are 1 m apart, where ordinary stainless steel thermal expansion will be affecting measurement by 10-20 µm, which is not acceptable in most cases. Accordingly, a preferred material of the object will not expand in size upon being exposed to higher temperatures, or expand very little, thus not significantly affecting the distance between the sensors. According to the first aspect at least three sensors, or at least four sensors may be arranged at fixed positions across the foil pathway and said sensors may be any one of a laser detector, an optical camera and a thermal camera, or a combination thereof. According to one alternative the sensor or sensors may be a laser detector or scanner. A laser detector a so called passive device which is designed to detect infrared emissions. A laser pulse is sent out from a transmitter to an object. The light particles are then scattered back from the object to a receiver. Laser detectors can survey the distance to a target by measuring the laser pulses reflected back from and object to the transmitter. Laser detectors are also called lidar detectors. The sensors may be arranged at fixed lateral and longitudinal positions across a width of said foil pathway. This means that the sensors are arranged at fixed positions depending on the width of the foil and coating to be processed in the roll-to-roll process, i.e. if a wider foil or substrate is conveyed the sensors may be adjusted to fixed positions suitable to detect the edges of the foil and coating respectively and for that width. The sensors may further be arranged to be synchronized with each other. This means that the sensor devices measures the distance at at exactly the same intervals, which is important for a high resolution measurement. According to the first aspect the sensors may be adapted to detect at least two edge portions of said coating material and at least two edge portions of said foil. The system may further comprise a processing device adapted to receive at least one signal from said sensors and wherein said processing device is adapted to calculate a width of said at least one layer of a coating material and a width of said foil material based on said signal. According to the first aspect the sensors may be adapted to detect a height of at least one layer of said coating material. Since the sensors are arranged at a fixed height above the foil or substrate the system is also able to detect, and calculate the thickness or height of the coating material layer or layers. The sensors may also be adapted to detect a height of at least a first layer of a coating material and at least a second layer of a coating material, wherein the second layer is arranged onto said first layer and wherein said first and second layers are the same or different coating material. This means the system is able to detect, or calculate, the thickness of each layer, even if the layers are arranged on top of each other. This however, requires that the dimensions of the second or top layer are smaller than the dimensions of the first or bottom layer. According to a second aspect there is provided a method for measuring a width of at least one layer of a coating material provided onto a foil material in a roll-to-roll process, wherein in said roll-to-roll process a foil material is provided with at least one layer of a coating material and wherein said foil material is transported along a foil pathway, wherein said method comprises: arranging at least two sensors at fixed positions across a width of said foil material (or foil pathway); transporting said foil material provided with at least one layer of a coating material along said foil pathway; detecting at least an edge portion of said foil material and said at least one layer of coating material respectively. The method according to the second aspect may further comprise providing a processing device; transmitting at least one detection signal from said sensors to said processing device; and calculating by said processing device at least a width of said coating material and/or said foil material. Said sensors may further be arranged in line with each other or off-set. The sensors may be arranged at a wet end of said roll-to-roll process, at a dry end of said roll- to-roll process or at both a wet and dry end of said roll-to-roll process. According to the second aspect at least three sensors, or at least four sensors may arranged in line with each other, or off-set, and at fixed positions across said foil. The sensors may be arranged at fixed lateral and longitudinal positions across a width of said foil (or foil pathway) and be arranged to be synchronized with each other. The synchronization allows for a high resolution of the sensors. The sensors may be any one of a laser detector, an optical camera and a thermal camera, or a combination thereof. According to one alternative the sensor or sensors are laser detector(s). The method of the second aspect may further comprise detecting a height of at least one layer of coating material. According to one alternative, the method of the second aspect further comprises detecting irregularities in the at least one edge portion of said coating material and along the foil pathway, and wherein said sensor operates at a frequency in the range of 25 to 75 Hz. These irregularities may for instance be waviness of the edge or edge portion. The frequency of the scanning is smaller than the irregularities detected, and may preferably be about 50 Hz. The width of the foil material may be in the range of 150 mm to 1500 mm, and the foil material may be provided with at a first layer of a coating material and a second layer of a coating material. The first coating material layer may be different from the second coating material layer, or the first coating material layer may be the same as the second coating material layer. The first material layer may be arranged on the second coating material layer, or wherein the second coating material layer is arranged on the first coating material layer, or wherein the first and second coating material layers are arranged aligned and side-by-side on said foil material. According to the second aspect the sensors may be arranged to detect a first and a second edge portion of said coating material layer and a first and a second edge portion of said foil material and wherein said first and second edge portions are positioned opposite each other The above-described measurement system and measurement method may be for, or comprised in, a process for manufacturing of a battery cell, or electrodes for a battery cell, for propelling a vehicle. The vehicle may for example be a fully electrically propelled vehicle or a hybrid vehicle. BRIEF DESCRIPTION OF THE DRAWINGS The embodiments disclosed herein are illustrated by way of example, and by not by way of limitation, in the figures of the accompanying drawings. Like reference numerals refer to corresponding parts throughout the drawings, in which Figure 1a is a schematic top view of a measurement system. Figure 1b is a schematic cross-sectional view of a measurement system. Figure 2 is a schematic top view of one measurement embodiment. DETAILED DESCRIPTION Embodiments of the present disclosure will now be described more fully hereinafter. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those persons skilled in the art. In the below the term foil, foil material or substrate or substrate material may be used interchangeably. It is to be understood as a flat or substantially flat material onto which a coating material is applied, such as trough spray coating or extrusion. The process is described as a roll-to-roll process. A roll-to-roll process is a any process where a material, such as a substrate or foil, is transported from at least a first roll to at least a second roll. The substrate or foil may however be transported vertically or horizontally, even though the figures illustrate a substrate moving along a horizontal pathway. Figure 1a illustrates a first embodiment of a measurement system 10 where at least two, or multiple, sensors 1, 1’ are arranged at fixed positions across the width W₁ of a foil or substrate material 2. A coating material 3 has been applied on the foil or substrate material 2. The width W₂ of the coating material is smaller than the width W₂ of the substrate material. The foil or substrate material 2 is transported or conveyed along a foil pathway 4 in a roll-to-roll process (not shown in the drawings). In the production of for instance electrodes for a cylindrical battery cell, the respective electrode materials are coated onto a substrate, which is provided from a first roll, and transported through a drying oven or chamber (i.e. an in-line dryer) to a second roll. The measurement system 1 may preferable be arranged at a wet side of the process, i.e. prior to the oven, but may also be arranged at the dry side, i.e. after the oven. The sensors 1 are arranged at fixed positions across the width W₁ of the foil. The position of the sensors may be fixed both with regards to the lateral and longitudinal position, i.e. at fixed places across the width and at fixed positions over, i.e. a specific height over, the pathway 4 of the foil or substrate. The sensors 1, 1’ may be arranged in line with each other or at off-set positions (not shown in the drawings). As illustrated in Fig 1b the sensors 1, 1’ are arranged to detect the edges E₁, E₂…E₆ or edge portions of the foil material 2 and coating material 3 respectively, in a cross-foil direction. By detecting the edge or edge portion is meant that, the sensor is able to differentiate between what is a coated portion and what is a foil or substrate. How the detection or differentiation is performed depends on the type of sensor used, and is describe in more detail below. The sensors 1, 1’ detects at least a first edge E₂ of the coating material 3 and a first edge E₁ of the substrate or foil material 2. Preferably, however, the sensors 1, 1’ detects also at least a second edge E₅ and E₆ of the respective materials, or if a second or subsequent coating layer 3’ has been applied the edges E₃, E₄ of that second coating layer 3’. The detection or differentiation is thus preferably performed across the width W₁ of the foil. It may also be adapted to measure the edge portions in a direction along the foil pathway 4. In response to detecting the edges or edge portions, the sensors 1, 1’ generate or provide a detection signal. The detection signal is transmitted or otherwise provide to a processing device or unit (not shown), which may be integrated with or placed remotely to the measurement system. The processing unit or device calculated, based on the detection signal and the placement of the sensors, as well at the velocity at which the materials are moving, a width W₁, W₂ of the respective layers. Further, as the sensors are arranged also at a fixed height above the foil pathway, the height H₁, H2 or thickness of the coating material can be detected, differentiated or calculated, based on the same principle as described for the width. The number of sensors 1, 1’, 1’’ arranged across the pathway 4, will depend on for instance the number of coating material layers 3, 3’ and/or the width of the foil material 2. The main inventive concept is that it is only the edges or edge portions that are detected by the sensors, thus requiring fewer sensors than in conventional measurement systems. The foil or substrate is conventionally moving at a speed or velocity of between 10 m/min and 150 m/min, depending on for instance the required time for drying or curing. The substrate or foil material conventionally has a width of between 300 mm and 1500 mm. The substrate foil may be coated on both sides of the foil. For instance in a process where electrode material for a cylindrical battery cell is produced one side may be coated with the cathode material and the other side with the anode material. The application of the coating may be performed sequentially or simultaneously. The coating layer 3 may be applied intermittently. This means that a portion of the substrate or foil may be covered with coating and a portion of the foil is left uncoated. The coating material layer 3 may also be applied across substantially the entire width of the foil or substrate or arranged in two or more separate portions along the length of the foil or substrate. The coating material layer 3 may also be applied in different shapes, such as rectangles, squares or any other suitable shape on the substrate. The coating material layer 3 may also be applied in different layers, such as for instance a first layer 3 applied directly on the substrate and a second layer 3’ applied on top of the first bottom layer, as illustrated in Fig.1b. The coating material 3 may further be the same or different, such as for instance a first layer 3 having a first composition and a second layer 3’ having a second composition, for instance with regards to adhesive ability etc.. The application of the coating material depends on the end use of the formed electrode. Electrodes for e.g. cylindrical battery cells could for instance either be formed as a continuous coating or as an intermittent coating. The measurement system and method described herein may be used for all types of coating material and foil materials. Conventionally the foil or substrate material is an aluminum or copper foil. The sensors may be as a working principle, laser detectors or laser distance measurers send out pulses of laser light. The light reflects off a solid surface, such as the coating material and foil material, and the detector or measurer calculates the amount of time it takes for the reflection to return to the device. A processing device, such as an internal processor then calculates distance based on how long it takes the reflection to return. Since the sensors, or laser detectors are arranged at fixed positions across the path of the foil and coating a very precise calculation of the width of the coating material can be achieved, by only detecting the edge or edge portion of the coating and foil material respectively. Further, as the sensors are arranged at a fixed height above the foil pathway, also the height of the coating material layer can be detected and calculated. The accuracy of a sensor is a measurement of the difference that can be expected between a sensor’s reading and the actual distance measured. The resolution is the smallest change in distance that a sensor can detect and is typically a smaller value than the accuracy error. Accuracy may be affected by temperature, target reflectance or ambient light, which generally will not affect the resolution. The preferred resolution of at least one sensor is below 5 µm, or even more preferred below 1 µm Preferably the laser sensors or detectors are synchronized. Whether using an array of single- point laser sensors across a large, moving surface or using a pair of sensors to measure differential thickness, it is important that the devices are working in unison and measuring distance at exactly the same intervals. In one embodiment, the system 1 and method according to the present disclosure may be used to detect irregularities in the edges or edge portions of the coating. As illustrated in Fig. 2 the edge portions E₂, E₄ of the coating material layer 3 may exhibit irregularities, such as “waviness”, which may occur during the application or extrusion of the coating material 3. When the measurement system 10 is used to detect this type of irregularities the scanning rate or detection rate of the sensors 1, 11 is set to be smaller, i.e. a smaller frequency, than the waves or irregularities. The measurement of irregularities may thus be performed in a lengthwise direction i.e. along the foil pathway 4 and/or in combination with the aforementioned cross-foil directional measurement. Preferably, the scanning frequency for a laser detector is set at to a range of 10 to 500 Hz, or preferably to 25 to 75 Hz, or even more preferably to about 50 Hz. Through the detection of irregularities, and measurement of a deviance from a desired width, a signal may be provide to, for instance air blowers, which may act on the signal to correct the dimensions of the coating material prior to introduction into the oven. This type of measurement and detection thus utilizes both the positioning of the sensors and the speed or velocity of the foil or substrate to calculate the irregularities and when they occur. Modifications and other variants of the described embodiments will come to mind to ones skilled in the art having benefit of the teachings presented in the foregoing description and associated drawings. Therefore, it is to be understood that the embodiments are not limited to the specific example embodiments described in this disclosure and that modifications and other variants are intended to be included within the scope of this disclosure. Furthermore, although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Therefore, persons skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the appended claims. As used herein, the terms “comprise/comprises” or “include/includes” do not exclude the presence of other elements or steps. Furthermore, although individual features may be included in different claims (or embodiments), these may possibly advantageously be combined, and the inclusion of different claims (or embodiments) does not imply that a certain combination of features is not feasible and/or advantageous. In addition, singular references do not exclude a plurality. Finally, reference numerals in the claims are provided merely as a clarifying example and should not be construed as limiting the scope of the claims in any way.

Claims

CLAIMS 1. A measurement system (10) adapted to arranged in connection with a roll-to-roll process, wherein in the roll-to-roll process a foil material (2) is provided with at least one layer of a coating material (3) and is arranged to be transported along a foil pathway (4), and wherein said measurement system (10) comprises: at least two sensors (1, 1’) arranged at fixed positions across a width (W₁) of said foil material (2); and wherein said sensors (1, 1’) are adapted to detect at least one edge portion (E₂) of said coating material and at least one edge portion (E₁) of said foil respectively.

2. The measurement system (10) according to claim 1, wherein said sensors (1,1’) are arranged in line with each other or arranged off-set at said fixed positions.

3. The measurement system (10) according to claim 1 or 2, wherein at least three sensors (1, 1’), or at least four sensors are arranged at fixed positions across the foil pathway (4).

4. The measurement system (10) according to any one of claims 1 to 3, wherein said sensor (1, 1’) is any one of a laser detector, an optical camera and a thermal camera, or a combination thereof.

5. The measurement system according to claim 4, wherein the sensor is a laser detector.

6. The measurement system (10) according to any of the preceding claims, wherein said sensors (1, 1’) are arranged at fixed lateral and longitudinal positions across a width of said foil pathway (4).

7. The measurement system (10) according to the preceding claims, wherein said sensors (1, 1’) are arranged to be synchronized with each other.

8. The measurement system (10) according to any one of the preceding claims, wherein said sensors are adapted to detect at least two edge portions of said coating material and at least two edge portions of said foil.

9. The measurement system (10) according to any one of the preceding claims, wherein said system further comprises a processing device adapted to receive at least one signal from said sensors (1, 1’) and wherein said processing device is adapted to calculate a width (W₂) of said at least one layer of a coating material and a width (W₁) of said foil material based on said signal.

10. The measurement system (10) according to any one of the preceding claims, wherein said sensors (1, 1’) are adapted to detect a height (H1) of at least one layer (3) of said coating material.

11. The measurement system (10) according to claim 6, wherein said sensors (1, 1’) are adapted to detect a first height (H₁) of at least a first layer (3) of a coating material and second height (H₂) at least a second layer (3’) of a coating material, wherein the second layer is arranged onto said first layer and wherein said first and second layers (3, 3’) are the same or different coating material.

12. The measurement system (10) according to any one of the preceding claims, wherein the at least two sensors (1, 1’) are physically joined by an object that fixates the distance between the sensors.

13. The measurement system (10) according to claim 12, wherein the object that fixates the distance between the sensors comprises, or are essentially composed of, a material with a coefficient of thermal expansion of below 5 ppm/^oC, preferably below 3 ppm/^oC, more preferably below 2 ppm/^oC.

14. A method for measuring a width (W₁) of at least one layer (3) of a coating material provided onto a foil material (2) in a roll-to-roll process, wherein in said roll-to-roll process a foil material (2) is provided with at least one layer of a coating material (3) and wherein said foil material (2) is transported along a foil pathway (4), wherein said method comprises: arranging at least two sensors (1, 1’) at fixed positions across a width (W₁) of said foil; transporting said foil material (2) provided with at least one layer of a coating material (3) along said foil pathway (4); detecting at least an edge portion (E₁) of said foil material and at least one edge portion (E₂) of said layer (3) of coating material.

15. The method according to claim 14, wherein said method further comprises: further providing a processing device; transmitting at least one detection signal from said sensors (1, 1’) to said processing device; and calculating by said processing device at least a width (W₂) of said coating material (3) and/or a width (W₁) of said foil material (2).

16. The method according to any one of claims 14 or 15, wherein said sensors (1, 1’) are further arranged in line with each other or off-set.

17. The method according to any one of claims 14 to 16, wherein said sensors (1, 1’) are arranged at a wet end of said roll-to-roll process, at a dry end of said roll-to-roll process or at both a wet and dry end of said roll-to-roll process.

18. The method according to any one of claims 14 to 16, wherein at least three sensors, or at least four sensors are arranged in line with each other and at fixed positions across said foil pathway.

19. The method according to any one of claims 14 to 18, wherein the sensors (1, 1’) are arranged at fixed lateral and longitudinal positions across a width of said foil (2).

20. The method according to any one of claims 14 to 19, wherein said sensors are arranged to be synchronized with each other.

21. The method according to any one of claims 14 to 129, wherein said sensors (1, 1’) are any one of a laser detector, an optical camera and a thermal camera, or a combination thereof.

22. The method according to claim 22, wherein the sensors (1, 1’) are laser detectors.

23. The method according to any one of claims 14 to 22, wherein the method further comprises detecting a height (H₁) of at least one layer of coating material (3).

24. The method according to any one of claims 14 to 23, wherein the method further comprises detecting irregularities in the at least one edge portion (E₂, E₄) of said coating material (3) and along the foil pathway (4), and wherein said sensors (1, 1’) operates at a frequency in the range of 25 to 75 Hz.

25. The method according to any one of claims 14 to 24, wherein a width (W₁) of the foil material (2) is in the range of 150 mm to 1500 mm.

26. The method according to any one of claims 14 to 25, wherein said foil material is provided with at a first layer (3) of a coating material and a second layer (3’) of a coating material.

27. The method according to claim 26, wherein the first coating material layer (3) is different from the second coating material layer (3’), or wherein the first coating material layer (3) is the same as the second coating material layer (3’).

28. The method according to aby one of claims 26 or 27, wherein said first coating material layer (3) is arranged on the second coating material layer (3’), or wherein the second material coating layer (3’) is arranged on the first material layer (3), or wherein the first and second coating material layers (3, 3’) are arranged aligned and side-by-side on said foil material (2).

29. The method according to any one of claims 14 to 28, wherein the sensors (1, 1’) are arranged to detect a first (E₂) and a second (E₄) edge portion of said coating material (3) layer and a first (E₁) and a second (E₆) edge portion of said foil material (2), and wherein said first ( E₁, E₂) and second ( E₄, E₆) edge portions are positioned opposite each other.