Method for inspecting electrode plates, method for manufacturing energy storage devices, and apparatus for inspecting electrode plates

Abstract

To correctly detect a recessed part on a coating material of an electrode plate.SOLUTION: An inspection for detecting a recessed part includes the steps of: diagonally applying linear light L1 extending in the width direction of an electrode plate 1 to the surface of a coating material 3, and moving the electrode plate 1 in the longitudinal direction; acquiring regular reflection light L2 of the light L1 by a coating material 3; dividing the acquired regular reflection light L2 in the width direction and obtaining a representative value of the brightness at multiple points in the longitudinal direction in each of the multiple regions in the width direction; determining a correction value for each region in the width direction such that the representative value of the brightness in the multiple regions in the width direction becomes the same; adding the correction value to the brightness of the regular reflection light L2 in each region in the width direction; and detecting a dark part with lower brightness than a predetermined threshold in the brightness distribution of the regular reflection light L2 after the correction value is added, and determining the detected dark part as a recessed part.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a method for inspecting an electrode plate, a method for manufacturing a power storage device, and an inspection apparatus for an electrode plate.

Background Art

[0002] For example, Patent Document 1 discloses a method for manufacturing a secondary battery including a coating step of forming a layer of an active material composite on a strip-shaped metal foil, a pressing step of increasing the density of the active material layer by pressing, and an inspection step of detecting an abnormality in the active material layer. In the inspection step disclosed in Patent Document 1, an abnormality such as an abnormal film thickness of the active material layer, a scratch on the active material layer, or a foreign substance mixed therein is detected as an abnormality.

[0003] Further, for example, Patent Document 2 discloses a lithium deposition inspection apparatus for detecting lithium deposited on the surface of a negative electrode composite layer of a lithium-ion secondary battery. In the inspection apparatus disclosed in Patent Document 2, white light is irradiated onto the negative electrode composite layer, and the deposited lithium is detected by acquiring image data of the reflected light. The inspection apparatus acquires the image data in RGB format and converts the information of each pixel of the image data into a hue angle and brightness. The inspection apparatus disclosed in Patent Document 2 determines whether there are pixels showing a hue angle and brightness specific to the case where lithium deposition exists.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] In some cases, depressions may occur on the surface of the coated material, where the area is lower than the surrounding area. When inspecting electrode plates, it is preferable to check whether depressions have occurred in the coated material. In principle, depressions can be detected by shining light on the coated material and obtaining the brightness distribution of the reflected light. Since the brightness of the reflected light in the depressions is lower than that of the normal areas, they can be detected. However, there are variations in the pressing of the coated material depending on the location, and this also causes variations in the brightness of the reflected light from the normal areas of the coated material depending on the location. Therefore, even if a brightness threshold is set to distinguish between the normal areas and the depressions, the depressions may not be detected correctly due to variations in the brightness of the normal areas. [Means for solving the problem]

[0006] The electrode plate inspection method proposed herein is a method for inspecting an electrode plate in which a coating material containing an active material has been coated onto a current collector plate and rolled, and includes an inspection for detecting depressions in the coating material. The inspection for detecting depressions includes the steps of: shining a linear light extending in the width direction of the electrode plate obliquely onto the surface of the coating material, and further moving the electrode plate in a longitudinal direction perpendicular to the width direction with respect to the light; acquiring specularly reflected light from the coating material; dividing the acquired specularly reflected light in the width direction and determining representative values ​​of the brightness at multiple locations in the longitudinal direction in each of the multiple regions in the width direction; determining a correction value for each region in the width direction such that the representative values ​​of the brightness in the multiple regions in the width direction are the same; adding the correction value to the brightness of the specularly reflected light in each region in the width direction; and detecting dark areas with a brightness lower than a predetermined threshold in the brightness distribution of the specularly reflected light after the correction value has been added, and determining the detected dark areas as depressions.

[0007] Furthermore, the electrode plate inspection apparatus proposed herein comprises: a conveying device for conveying an electrode plate, which has been coated with a coating material containing an active material and rolled onto a current collector plate, in its longitudinal direction; an illumination device for obliquely irradiating the surface of the coating material on the electrode plate being conveyed by the conveying device with linear light extending in the width direction of the electrode plate; an acquisition device positioned on the path of the specularly reflected light from the coating material irradiated by the illumination device, and sequentially acquiring specularly reflected light from multiple locations in the longitudinal direction of the coating material; and a determination device for determining the presence or absence of depressions in the coating material. The determination device comprises a first processing unit, a second processing unit, a third processing unit, and a fourth processing unit. The first processing unit divides the specularly reflected light acquired by the acquisition device in the width direction and determines a representative value of the brightness at multiple locations in the longitudinal direction in each of the multiple regions in the width direction. The second processing unit determines a correction value for each region in the width direction such that the representative value of the brightness in the multiple regions in the width direction is the same. The third processing unit adds the correction value to the brightness of the specularly reflected light in each region in the width direction. The fourth processing unit detects dark areas with a brightness lower than a predetermined threshold in the brightness distribution of the specularly reflected light after the correction value has been added, and determines the detected dark areas to be depressions.

[0008] According to the above-described electrode plate inspection method and inspection apparatus, by irradiating the surface of the coated material with linear light at an oblique angle and obtaining specularly reflected light, the difference in brightness between normal areas and depressed areas can be increased compared to, for example, diffuse illumination, making it easier to distinguish between normal areas and depressed areas. Furthermore, by determining representative brightness values ​​at multiple locations in the longitudinal direction for each of the multiple regions set in the width direction of the electrode plate, and determining a correction value for each region such that the above representative values ​​are the same, variations in brightness depending on the location on the coated material can be corrected. As a result, the brightness of the normal areas after correction becomes uniform, and depressed areas can be correctly detected based on a threshold. [Brief explanation of the drawing]

[0009] [Figure 1] This is a schematic side view of an electrode plate inspection device. [Figure 2]This is a schematic diagram of an image taken near the sinkhole. [Figure 3] This is a flowchart showing the inspection process for electrode plates. [Figure 4] This graph shows an example of the brightness distribution of specularly reflected light. [Figure 5] This is a graph of average brightness, illustrating an example of how correction values ​​are calculated. [Figure 6] This graph shows the brightness distribution of specularly reflected light after correction. [Modes for carrying out the invention]

[0010] The following describes one embodiment of the electrode plate inspection device. It should be noted that the embodiment described herein is not intended to limit the present invention. Furthermore, the figures are schematic diagrams and do not necessarily faithfully reflect actual implementations. In the following, components and parts that perform the same function are denoted by the same reference numerals, and redundant explanations are omitted or simplified as appropriate.

[0011] [Configuration of electrode plate inspection device] Figure 1 is a schematic side view of the electrode plate inspection device 10. The electrode plate 1 to be inspected by the electrode plate inspection device 10 is an electrode plate of an energy storage device, such as a lithium-ion secondary battery. In this specification, "energy storage device" is a term that refers to all devices that can be repeatedly charged and discharged, and is a concept that includes chemical batteries such as lithium-ion secondary batteries and nickel-metal hydride batteries, and physical batteries such as electric double-layer capacitors.

[0012] As shown in Figure 1, the electrode plate 1 is formed in a strip shape by coating a current collector plate 2 with a coating material 3 containing an active material. The electrode plate inspection device 10 inspects whether there are any depressions 5 (see Figure 2) on the surface of the coating material 3. A depression 5 is a defect that is recessed compared to the surrounding normal portion 4 (see Figure 2). The electrode plate inspection device 10 inspects the electrode plate 1 for depressions 5 after the coating material 3 has been applied to the current collector plate 2 and rolled (after the pressing process).

[0013] In this embodiment, the electrode plate inspection device 10 inspects the negative electrode plate 1, which is coated with a coating material 3 containing a negative electrode active material onto the negative electrode current collector plate 2. Positive ions tend to precipitate in defects in the coating material 3 of the negative electrode plate 1. Therefore, inspection of depressions 5 on the negative electrode plate 1 is more important than that of the positive electrode plate. However, the electrode plate inspection device 10 may also be used to inspect for the presence or absence of depressions on the positive electrode plate.

[0014] As shown in Figure 1, the electrode plate inspection device 10 includes a transport device 20, a lighting device 30, a reflected light acquisition device 40, and a determination device 50 that determines the presence or absence of a recessed portion 5 (see Figure 2).

[0015] The conveying device 20 conveys the electrode plate 1 in its longitudinal direction. The longitudinal direction of the electrode plate 1 is perpendicular to the width direction of the electrode plate 1. As shown in Figure 1, the conveying device 20 is equipped with conveying rollers 21 that are in contact with the back surface of the electrode plate 1 to which the coating material 3 is applied and convey the electrode plate 1.

[0016] The lighting device 30 obliquely irradiates the surface of the coating material 3 of the electrode plate 1 being transported by the transport device 20 with linear light L1 (hereinafter also referred to as inspection light L1) extending in the width direction of the electrode plate 1. The lighting device 30 includes a light source (not shown) and a slit 31 that generates linear inspection light L1.

[0017] The acquisition device 40 is disposed on the path of the specularly reflected light L2 of the inspection light L1 irradiated by the lighting device 30 on the coating material 3. Here, the "path of the specularly reflected light L2" means a position where the specularly reflected light L2 can be substantially received, and for example, it may be a position slightly deviated from the center of the calculated path. The acquisition device 40 is configured to acquire the specularly reflected light L2 by the coating material 3. The acquisition device 40 is, for example, a camera. As the electrode plate 1 is conveyed in the longitudinal direction by the conveying device 20, the acquisition device 40 sequentially acquires the specularly reflected light L2 at a plurality of positions in the longitudinal direction of the coating material 3. The acquisition device 40 acquires the specularly reflected light L2, for example, at every predetermined sampling period. The specularly reflected light L2 acquired by the acquisition device 40 is distributed along the width direction of the electrode plate 1 and is also distributed in the longitudinal direction by being sequentially acquired in the longitudinal direction. That is, the acquisition device 40 acquires the surface distribution of the specularly reflected light L2 along the surface of the electrode plate 1.

[0018] FIG. 2 is a schematic diagram of an image obtained by imaging the vicinity of the recess 5. Such an image is obtained by imaging the surface distribution of the specularly reflected light L2 along the surface of the electrode plate 1 acquired by the acquisition device ”. As shown in FIG. 2, the recess 5 is recognized as a dark portion 6 having a lower brightness than the surrounding normal portion 4 (represented by hatching in FIG. 2). Since the acquisition device 40 acquires the specularly reflected light L2 of the inspection light L1 obliquely irradiated to the recess 5, the longitudinal direction of the electrode plate 1 in the recess 5 of the image is compressed and is elliptical. According to the findings of the inventors of the present application, the brightness difference between the normal portion 4 and the recess 5 is larger, for example, under the condition of irradiating non-diffused light by the slit 31 from the lighting device 30 to acquire the specularly reflected light than under the condition of irradiating diffused light from the lighting device 30 to acquire the reflected light. Therefore, it is easy to detect the recess 5 by using the specularly reflected light L2.

[0019] According to the findings of the inventor of the present application, the recessed portion 5 is mainly generated by the escape of air bubbles in the coating material 3 before the pressing process. In the pressing process, when the air bubbles escape, the peripheral portion 7 of the raised recessed portion 5 is rolled particularly strongly and becomes smooth. Therefore, the peripheral portion 7 is likely to specularly reflect the inspection light L1 (hereinafter, also referred to as having a high specular reflectance), and has a particularly high brightness in the image. On the other hand, the recessed portion 5 is not rolled in the pressing process and does not flatten. Therefore, the recessed portion 5 is likely to diffusely reflect the inspection light L1 (hereinafter, also referred to as having a low specular reflectance), and has a low brightness in the image.

[0020] The determination device 50 is connected to the acquisition device 40 and determines the presence or absence of the recessed portion 5 of the coating material 3. As shown in FIG. 1, the determination device 50 includes a first processing unit 51, a second processing unit 52, a third processing unit 53, a fourth processing unit 54, and a fifth processing unit 55. The configuration of the determination device 50 is not particularly limited. The determination device 50 may be incorporated in the electrode plate inspection device 10, or may be configured by a computer or the like connected to the electrode plate inspection device 10. The determination device 50 may include a storage device (such as a memory) and an arithmetic device (such as a CPU), and each function may be appropriately embodied by the cooperation of physical components and control based on the calculation results performed in accordance with a predetermined program.

[0021] The first processing unit 51 divides the specularly reflected light L2 acquired by the acquisition device 40 in the width direction of the electrode plate 1, and obtains representative values of the brightness at a plurality of locations in the longitudinal direction in each of a plurality of regions R1 to Rm (see FIG. 4) in the width direction. In the present embodiment, the first processing unit 51 calculates an average value as the representative value of the brightness. However, the representative value of the brightness at a plurality of locations is not limited to the average value, and may be, for example, a median value or the like.

[0022] As will be illustrated later, the pressing of the coating material 3 in the pressing process tends to be stronger in the center in the width direction and weaker at the edges. Therefore, the center of the coating material 3 in the width direction has high smoothness and high specular reflectance. On the other hand, the edges of the coating material 3 in the width direction have lower smoothness and lower specular reflectance than the center. Therefore, the brightness of the specular reflected light L2 varies across multiple regions R1 to Rm in the width direction. The representative value of brightness obtained by the first processing unit 51 tends to be higher in the central region and lower at the edges among the multiple regions R1 to Rm in the width direction.

[0023] The second processing unit 52 determines a correction value for each of the multiple regions R1 to Rm in the width direction such that the representative value of brightness in each region R1 to Rm is the same. The third processing unit 53 adds the correction value determined by the second processing unit 52 to the brightness of the specularly reflected light in each of the regions R1 to Rm in the width direction. Through this process, the difference in brightness of the specularly reflected light L2 after correction in the multiple regions R1 to Rm is reduced.

[0024] The fourth processing unit 54 detects dark areas with lower brightness than a predetermined threshold T1 (see Figure 6) in the brightness distribution of specularly reflected light L2 after the correction value has been added, and determines the detected dark areas to be depressions 5. The fifth processing unit 55 determines the electrode plate 1 to be defective if a predetermined number or more dark areas 6 (see Figure 2) of a predetermined size or larger are detected.

[0025] [Electrode Plate Inspection Process] Figure 3 is a flowchart of the inspection process for the electrode plate 1. The inspection of the electrode plate 1 involves detecting the recessed portion 5 and determining whether the electrode plate 1 is good or bad based on this detection. As shown in Figure 3, in step S01 of the inspection of the electrode plate 1, a linear inspection light L1 extending in the width direction of the electrode plate 1 is irradiated obliquely onto the surface of the coating material 3. In step S01, the electrode plate 1 is further moved in the longitudinal direction relative to the inspection light L1. In this embodiment, the inspection light L1 is stationary and the electrode plate 1 is transported by the transport device 20, but the inspection light L1 may also be moved.

[0026] In step S02, the specular reflected light L2 of the inspection light L1 by the coating material 3 is acquired by the acquisition device 40. The specular reflected light L2 is acquired simultaneously at multiple locations in the width direction of the electrode plate 1, and is also acquired at multiple locations in the longitudinal direction as the electrode plate 1 moves in the longitudinal direction relative to the inspection light L1. In this embodiment, the specular reflected light L2 at multiple locations in the longitudinal direction is acquired while the electrode plate 1 is continuously moved in the longitudinal direction. However, the method of acquiring the distribution of specular reflected light L2 is not limited to this. The distribution of specular reflected light L2 may be acquired, for example, while the electrode plate 1 is intermittently transported.

[0027] Figure 4 is a graph showing an example of the brightness distribution of specularly reflected light L2. Graph G1 in Figure 4 shows the brightness distribution of specularly reflected light L2 at a single position in the longitudinal direction. The horizontal axis in Figure 4 represents the position in the width direction of the electrode plate 1, and the vertical axis represents brightness. The diagram above graph G1 is a schematic diagram showing the electrode plate 1 at the location corresponding to graph G1.

[0028] As shown in Graph G1, the brightness of specularly reflected light L2 is high in the center of the coated material 3 and low at the edges. However, depending on the pressing process, the brightness of specularly reflected light L2 may vary in a different way than described above. There is no particular pattern to the variation in the brightness of specularly reflected light L2 depending on the location on the coated material 3. Furthermore, as shown in Figure 4, the brightness of specularly reflected light L2 from the uncoated portion 2a of the current collector plate 2, where the coated material 3 is not applied, is higher than the brightness of specularly reflected light L2 from the coated material 3.

[0029] As shown in the upper diagram of Figure 4, in this example, the coating material 3 is assumed to have multiple depressions 5. The brightness of each depression 5 is lower than the brightness of the surrounding normal area 4. In graph G1, the valleys Ga with low brightness indicate depressions 5. Depressions 5 can be identified by the difference in brightness from the surrounding normal area 4. However, since the brightness of the normal area 4 differs among multiple regions R1 to Rm, even if a common threshold is set to distinguish between the normal area 4 and the depression 5, it may not be possible to correctly detect the depressions 5. For example, as shown in Figure 4, if the threshold is T0, depressions 5 can be detected in the central part of the multiple regions R1 to Rm. However, at the edges, the brightness of the normal area 4 is less than the threshold T0, and depressions 5 cannot be correctly detected. In this embodiment, this is resolved in the following steps.

[0030] In step S03, the specular reflected light L2 acquired in step S02 is divided in the width direction of the electrode plate 1, and representative values ​​of brightness at multiple locations in the longitudinal direction are obtained for each of the multiple regions R1 to Rm in the width direction. In this embodiment, a predetermined distance (e.g., 1 m) is set as the processing unit, and representative values ​​are obtained from multiple brightness data acquired while the electrode plate 1 is transported in the longitudinal direction for the predetermined distance. That is, representative values ​​are calculated for each predetermined distance in the longitudinal direction. Here, the average value is obtained as the representative value. The multiple regions R1 to Rm in the width direction may be set arbitrarily as much as possible under the detection resolution of the acquisition device 40. By obtaining representative values ​​of brightness at multiple locations in the longitudinal direction, the standard brightness of the normal portion 4 of each region R1 to Rm can be determined. Even if a depression 5 exists within the region, the area of ​​the depression 5 is small compared to the area of ​​the normal portion 4, so the presence of the depression 5 has almost no effect on the representative value of brightness.

[0031] In step S04, correction values ​​are determined for each of the multiple regions R1 to Rm in the width direction such that the representative value of brightness in each region is the same. These correction values ​​are designed to eliminate the differences between the representative values ​​of brightness in the multiple regions R1 to Rm in the width direction. By adding these correction values ​​to the representative values ​​of brightness in each of the multiple regions R1 to Rm in the width direction, the representative values ​​of brightness after adding the correction values ​​become the same across the multiple regions R1 to Rm. Figure 5 is a graph of average brightness showing an example of the method for calculating the correction values. Graph G2 in Figure 5 is the graph of average brightness obtained in step S03. Graph G3 is obtained by adding each correction value obtained in step S04 to graph G2. In the method shown in Figure 5, the correction values ​​are determined so that the brightness of the other regions is matched to the region Rmax, which has the highest average brightness in graph G2. As shown in Figure 5, for example, correction value C1 is set for region R1 and correction value Cm is set for region Rm. As a result, the average brightness values ​​of multiple regions R1 to Rm in the width direction become consistent, as shown in graph G3. Let this corrected average brightness be B1.

[0032] However, the method shown in Figure 5 is just one example, and the method for calculating the correction values ​​is not limited to the above. For example, each correction value may be determined so that the brightness of each region R1 to Rm after correction is equal to a predetermined brightness. In that case, some or all of the correction values ​​may be negative.

[0033] In step S05, a correction value is added to the brightness of the specularly reflected light L2 in each region R1 to Rm in the width direction. Figure 6 is a graph showing the brightness distribution of the corrected specularly reflected light L2. As shown in graph G4 of Figure 6, the corrected brightness of the specularly reflected light L2 from the normal portion 4 is generally uniform regardless of its position in the width direction of the coated material 3. Furthermore, the corrected brightness of the specularly reflected light L2 from the normal portion 4 is close to the corrected average brightness B1 (see Figure 5). The corrected brightness of the recessed portion 5 is lower than the corrected brightness of the normal portion 4.

[0034] In step S06, in the brightness distribution of specularly reflected light L2 after the correction value has been added, dark areas Gb with a brightness lower than a predetermined threshold T1 are detected, and the detected dark areas Gb are determined to be depressions 5. The dark areas Gb in graph G4 correspond to the dark areas 6 in the image in Figure 2. The brightness of the corrected normal portion 4 is generally uniform regardless of the position in the width direction of the coating material 3, as determined in step S05. Therefore, as shown in Figure 6, the influence of variations in the brightness of specularly reflected light L2 depending on the position on the coating material 3 is suppressed, and depressions 5 can be correctly detected based on the predetermined threshold T1.

[0035] The "predetermined" threshold T1 may be a threshold predetermined relative to the corrected average brightness B1 (or other representative brightness). For example, the threshold T1 may be defined as the difference from the corrected average brightness B1. The threshold T1 may also be defined as the absolute value of brightness. For example, if the correction value is calculated so that the corrected average brightness B1 becomes a predetermined brightness, the threshold T1 may be the absolute value of brightness. Alternatively, if the quality of the pressing process is stable, it is possible to define the threshold T1 as the absolute value of brightness regardless of the method for calculating the correction value.

[0036] In step S07, it is determined whether a predetermined number or more dark areas 6 of a predetermined size or larger are detected. As shown in Figure 3, if the number of dark areas 6 of a predetermined size or larger (simply referred to as "dark areas" in Figure 3) is less than the predetermined number (if the result of step S07 is YES), in step S08, the electrode plate 1 is determined to be good with respect to the recessed areas 5. If a predetermined number or more dark areas 6 of a predetermined size or larger are detected (if the result of step S07 is NO), in step S09, the electrode plate 1 is determined to be defective. In this embodiment, even if dark areas 6 smaller than the predetermined size are detected, they are not used to determine whether the electrode plate 1 is good or bad. The size of the dark area 6 is represented here by the length of the dark area 6 on the image (see Figure 2) in the width direction of the electrode plate 1. However, the size of the dark area 6 may also be represented by other criteria (for example, the area of ​​the dark area 6). The predetermined number of dark areas 6 may be one or two or more.

[0037] [Effects of the Embodiment] The following describes the effects and advantages that can be achieved by the electrode plate inspection device 10 according to this embodiment and the inspection method using it.

[0038] The electrode plate inspection apparatus 10 according to this embodiment includes an illumination device 30 that obliquely irradiates the surface of the coating material 3 of the electrode plate 1 being transported by a transport device 20 with linear inspection light L1 extending in the width direction of the electrode plate 1; an acquisition device 40 positioned on the path of the specular reflected light L2 from the coating material 3 of the inspection light L1 irradiated by the illumination device 30, and sequentially acquires specular reflected light L2 at multiple locations in the longitudinal direction of the coating material 3; and a determination device 50 that determines the presence or absence of depressions 5 in the coating material 3. The determination device 50 includes a first processing unit 51 to a fourth processing unit 54. The first processing unit 51 divides the specular reflected light L2 acquired by the acquisition device 40 in the width direction of the electrode plate 1 and determines representative values ​​of the brightness at multiple locations in the longitudinal direction of the electrode plate 1 in each of the multiple regions R1 to Rm in the width direction. The second processing unit 52 determines a correction value for each of the multiple regions R1 to Rm in the width direction such that the representative values ​​of the brightness in the multiple regions R1 to Rm in the width direction are the same. The third processing unit 53 adds a correction value to the brightness of the specularly reflected light L2 in each region R1 to Rm in the width direction. The fourth processing unit 54 detects dark areas Gb with a brightness lower than a predetermined threshold T1 in the brightness distribution of the specularly reflected light L2 after the correction value has been added, and determines the detected dark areas Gb to be depressions 5. With this electrode plate inspection device 10, for the reasons described above, depressions 5 can be correctly detected regardless of the variation in brightness of the specularly reflected light L2 depending on the position on the coating material 3.

[0039] In this embodiment, the first processing unit 51 is configured to calculate an average value as a representative value of brightness. In this embodiment, it is considered that there is no significant bias in brightness at multiple locations along the longitudinal direction of the electrode plate 1. Therefore, the average value is highly reliable as a representative value of multiple values.

[0040] In this embodiment, the determination device 50 includes a fifth processing unit 55 that determines the electrode plate 1 to be defective when a predetermined number or more dark areas 6 of a predetermined size or larger are detected. With this configuration, dark areas 6 smaller than the predetermined size are not used in determining the quality of the electrode plate 1. Therefore, it is possible to prevent an increase in the defect rate of the electrode plate 1 due to over-engineering.

[0041] In this embodiment, the electrode plate 1 is a negative electrode plate formed by coating a current collector plate 2 with a coating material 3 containing a negative electrode active material and then rolling it. Positive ions tend to precipitate in defects in the coating material 3 of the negative electrode plate 1. Therefore, inspection of the depressions 5 is particularly important for the negative electrode plate 1.

[0042] The above describes one embodiment of the electrode plate inspection apparatus proposed herein. However, the above embodiment is merely an example, and the invention can be implemented in other ways. The above-described embodiment does not limit the present invention unless otherwise specifically mentioned. Furthermore, the technology disclosed herein can be modified in various ways, and each component and each process mentioned herein can be omitted or combined as appropriate, unless no particular problems arise.

[0043] This Specification includes the disclosures set forth in the following sections:

[0044] Section 1: A method for inspecting an electrode plate that has been coated with a coating material containing an active material and rolled into a current collector plate, This includes an inspection to detect the recessed portion of the coating material, The inspection for detecting the aforementioned depression is, The process involves shining a linear beam of light extending in the width direction of the electrode plate obliquely onto the surface of the coating material, and further moving the electrode plate in a longitudinal direction perpendicular to the width direction with respect to the light, A step of obtaining specularly reflected light from the coating material, The process involves dividing the acquired specularly reflected light in the width direction and determining representative values ​​of the brightness at multiple locations in the longitudinal direction within each of the multiple regions in the width direction. A step of determining a correction value for each of the multiple regions in the width direction such that the representative value of brightness in each of the multiple regions in the width direction is the same, A step of adding the correction value to the brightness of the specularly reflected light in each region in the width direction, The process includes detecting dark areas with lower brightness than a predetermined threshold in the brightness distribution of the specularly reflected light after the correction value has been added, and determining that the detected dark areas are depressions. Method for inspecting electrode plates.

[0045] Section 2: The representative value of the aforementioned brightness is the average value. The inspection method for the electrode plate described in item 1.

[0046] Section 3: The inspection for detecting the depressions includes a step of determining the electrode plate to be defective if a predetermined number of dark areas of a predetermined size or larger are detected. The method for inspecting electrode plates as described in item 1 or 2.

[0047] Section 4: The electrode plate is a negative electrode plate in which a coating material containing a negative electrode active material is coated onto a current collector plate and then rolled. The method for inspecting electrode plates described in any one of items 1 to 3.

[0048] Section 5: A method for manufacturing an energy storage device, comprising a method for inspecting electrode plates as described in any one of items 1 to 4.

[0049] Item 6: A conveying device for transporting electrode plates, which have been coated with a coating material containing an active material and rolled, in the longitudinal direction thereof, An illumination device that irradiates the surface of the coating material on the electrode plate being transported by the transport device with linear light extending in the width direction of the electrode plate at an oblique angle, An acquisition device is positioned on the path of specularly reflected light from the coating material, which is irradiated by the aforementioned lighting device, and sequentially acquires specularly reflected light from multiple locations in the longitudinal direction of the coating material. The system includes a determination device for determining the presence or absence of depressions in the coating material, The determination device is A first processing unit that divides the specularly reflected light acquired by the acquisition device in the width direction and determines representative values ​​of the brightness at multiple locations in the longitudinal direction in each of the multiple regions in the width direction, A second processing unit that determines a correction value for each of the multiple regions in the width direction such that the representative value of brightness in those regions is the same, A third processing unit that adds the correction value to the brightness of the specularly reflected light in each region in the width direction, The system includes a fourth processing unit that detects dark areas with a brightness lower than a predetermined threshold in the brightness distribution of the specularly reflected light after the correction value has been added, and determines that the detected dark areas are depressions. An inspection device for electrode plates.

[0050] Section 7: The first processing unit calculates an average value as a representative value of the brightness. An inspection apparatus for electrode plates as described in item 6.

[0051] Section 8: The determination device includes a fifth processing unit that determines the electrode plate to be defective when a predetermined number of dark areas of a predetermined size or larger are detected. An inspection apparatus for electrode plates as described in item 6 or 7.

[0052] Section 9: The electrode plate is a negative electrode plate in which a coating material containing a negative electrode active material is coated onto a current collector plate and then rolled. An electrode plate inspection apparatus as described in any one of items 6 to 8. [Explanation of symbols]

[0053] 1 Electrode plate 2 Current collector plates 2a Uncoated area 3. Coating materials 4 Normal part 5. Sinkhole 6. Dark areas (image) 7 Peripheral area 10 Electrode Plate Inspection Device 20 Conveying device 21 Conveyor rollers 30 Lighting devices 31 slits 40 Acquisition device 50 Judgment device 51 First Processing Unit 52 Second Processing Unit 53 Third Processing Unit 54 Section 4 55. Section 5 L1 Inspection light (light) L2 Specular reflection light R1~Rm: Region in the width direction B1 Corrected average brightness C1, Cm correction value T1 threshold Gb dark area (data)

Claims

1. A method for inspecting an electrode plate that has been coated with a coating material containing an active material and rolled into a current collector plate, This includes an inspection to detect the recessed portion of the coating material, The inspection for detecting the aforementioned depression is, The process involves shining a linear beam of light extending in the width direction of the electrode plate obliquely onto the surface of the coating material, and further moving the electrode plate in a longitudinal direction perpendicular to the width direction with respect to the light, The process involves sequentially acquiring the specularly reflected light from the coating material at multiple locations in the longitudinal direction while the electrode plate is transported a predetermined distance in the longitudinal direction, The process involves dividing the acquired specularly reflected light in the width direction, and in each of the multiple regions in the width direction, calculating the average value of the brightness at multiple locations in the longitudinal direction from the brightness data of the specularly reflected light acquired at multiple locations in the longitudinal direction. A step of determining a correction value for each of the multiple regions in the width direction such that the average value of the brightness in those regions is the same, A step of adding the correction value to the brightness of the specularly reflected light in each region in the width direction, The process includes detecting dark areas with lower brightness than a predetermined threshold in the brightness distribution of the specularly reflected light after the correction value has been added, and determining that the detected dark areas are depressions. Method for inspecting electrode plates.

2. The inspection for detecting the depressions includes a step of determining the electrode plate to be defective if a predetermined number of dark areas of a predetermined size or larger are detected. The method for inspecting an electrode plate according to claim 1.

3. The electrode plate is a negative electrode plate in which a coating material containing a negative electrode active material is coated onto a current collector plate and then rolled. The method for inspecting an electrode plate according to claim 1.

4. A method for manufacturing an energy storage device, comprising a method for inspecting an electrode plate according to any one of claims 1 to 3.

5. A conveying device for transporting electrode plates, which have been coated with a coating material containing an active material and rolled, in the longitudinal direction thereof, An illumination device that irradiates the surface of the coating material on the electrode plate being transported by the transport device with linear light extending in the width direction of the electrode plate at an oblique angle, An acquisition device is positioned on the path of specularly reflected light from the coating material, which is irradiated by the lighting device, and sequentially acquires specularly reflected light from multiple locations in the longitudinal direction of the coating material while the electrode plate is transported a predetermined distance in the longitudinal direction. The system includes a determination device for determining the presence or absence of depressions in the coating material, The determination device is A first processing unit divides the specularly reflected light acquired by the acquisition device in the width direction, and in each of the multiple regions in the width direction, calculates the average value of the brightness at multiple locations in the longitudinal direction from the brightness data of the specularly reflected light acquired at multiple locations in the longitudinal direction. A second processing unit that determines a correction value for each of the multiple regions in the width direction such that the average value of the brightness in those regions is the same, A third processing unit that adds the correction value to the brightness of the specularly reflected light in each region in the width direction, The system includes a fourth processing unit that detects dark areas with a brightness lower than a predetermined threshold in the brightness distribution of the specularly reflected light after the correction value has been added, and determines that the detected dark areas are depressions. An inspection device for electrode plates.

6. The determination device includes a fifth processing unit that determines the electrode plate to be defective when a predetermined number of dark areas of a predetermined size or larger are detected. The electrode plate inspection apparatus according to claim 5.

7. The electrode plate is a negative electrode plate in which a coating material containing a negative electrode active material is coated onto a current collector plate and then rolled. The electrode plate inspection apparatus according to claim 5.

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