Method and system for analyzing electrode surfaces

Abstract

The present invention relates to an electrode surface analysis method and an electrode surface analysis system, and more specifically, to an electrode surface analysis method and an electrode surface analysis system that use a hyperspectral CCD to precisely analyze foreign matter remaining on the electrode surface during the electrode manufacturing process, thereby improving process efficiency and product reliability.

Description

Technical Field

[0001] Cross-reference to related applications This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0041537 filed on March 27, 2024, and all the contents disclosed in the documents of the corresponding Korean patent application are incorporated herein by reference.

[0002] The present invention relates to a method and a system for analyzing an electrode surface for analyzing the electrode surface during a manufacturing process of a secondary battery, and for precisely analyzing foreign substances on the electrode surface.

Background Art

[0003] As the development of technologies and the demand for mobile devices increase, the demand for secondary batteries as an energy source has been rapidly increasing, and accordingly, many studies have been conducted on secondary batteries that can meet various requirements.

[0004] Such secondary batteries are manufactured in a form in which an electrode assembly is built into a battery case together with an electrolyte. The electrode assembly is classified into a stack type, a folding type, a stack-folding type, etc. according to the manufacturing method. In the case of a stack type or stack-folding type electrode assembly, a unit assembly has a structure in which a positive electrode and a negative electrode are sequentially stacked with a separator interposed therebetween. In order to make such an electrode assembly, it is necessary to first manufacture a positive electrode and a negative electrode on which electrode tabs are formed.

[0005] The electrode process for manufacturing electrodes of a secondary battery includes (1) a mixing process, (2) a coating process, (3) a rolling process, and (4) a slitting and notching process, and these processes are performed in an in-line process.

[0006] The mixing step described above (1) is a step in which a slurry is manufactured for forming the active material layer of the electrode. The slurry can be manufactured by weighing and mixing various raw materials necessary for forming the active material layer, including the electrode active material, binder, and conductive material.

[0007] Furthermore, the coating step (2) is a step of thinly coating the slurry onto the current collector and drying it to form an electrode active material layer. The structure including the current collector and the electrode active material layer formed on the current collector is called an electrode sheet.

[0008] Furthermore, the rolling process (3) is a process of passing the electrode sheet between two rolls to stretch it to a constant length. The rolling process is also called the roll press process.

[0009] Furthermore, the (4) slitting and notching process is a process of cutting the electrode sheet to match the size of the battery. The slitting process can cut the battery sheet in the longitudinal direction according to the battery design standard. The notching process is a process of forming V grooves and electrode tabs after the slitting process. In this notching process, the electrode sheet is generally positioned on a die, and a part of the electrode sheet can be punched out using a press, or the electrode tabs can be formed by etching. On the other hand, in a small pouch line, there may be an etching process between the rolling process and the slitting process.

[0010] However, there is a possibility that foreign matter generated during such etching processes may remain on the electrode surface, leading to a decrease in electrode quality. If the type and amount of foreign matter remaining on the electrode surface could be identified, the etching process could be designed and implemented to minimize the generation of this foreign matter. Here, "foreign matter" refers to residues such as binders contained in the active material layer of the electrode.

[0011] Generally, vision cameras installed in inline equipment for the inline process of electrode manufacturing are used to check for the presence or absence of remaining foreign matter. However, vision cameras have a large field of view (FOV), so they can only confirm the presence or absence of remaining foreign matter, and it is difficult to specifically confirm the type and amount of remaining foreign matter. The electrode etching process is performed inline, and due to the limitations of the inline equipment, it is necessary to install vision cameras, and there were technical limitations to installing a camera that could analyze foreign matter more precisely in addition to the vision camera.

[0012] Therefore, there is a need to develop a technology for analyzing the electrode surface that can confirm the type and amount of foreign matter remaining on the electrode surface after the etching process. [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Korean Published Patent No. 2011-0029011 [Overview of the Initiative] [Problems that the invention aims to solve]

[0014] As a result of extensive research conducted to solve the aforementioned problems, the inventors confirmed that by introducing a hyperspectral CCD (Charge Coupled Device) as an offline device, in addition to the vision camera (vision), which is an in-line device provided in the in-line process for manufacturing electrodes, the electrode surface can be analyzed more precisely.

[0015] Therefore, an object of the present invention is to provide a method for analyzing electrode surfaces using a hyperspectral CCD.

[0016] Another object of the present invention is to provide an analysis system for electrode surfaces using a hyperspectral CCD. [Means for solving the problem]

[0017] To achieve the above objective, the present invention provides an electrode surface analysis method using a hyperspectral CCD (Charge Coupled Device), (a) A step of taking an image of the electrode surface with a hyperspectral CCD and obtaining the spectrum of the electrode surface; (b) A step of visualizing the electrode surface using the spectrum of the electrode surface; and (c) A method for analyzing an electrode surface is provided, which includes the step of quantifying the visualized electrode surface.

[0018] In one embodiment of the present invention, in step (a), the spectrum showing the correlation between wavelength and intensity of brightness of the electrode surface captured by the hyperspectral CCD is used. After selecting the average or median brightness value corresponding to a wavelength region with a large brightness gap between two types selected from the group consisting of the surface of the current collector, the surface of the electrode active material layer, and foreign matter included in the electrode surface, The present invention provides an electrode surface analysis method that divides the electrode surface into individual regions, including the surface of the current collector, the surface of the electrode active material layer, and foreign matter, based on the aforementioned discrimination criteria.

[0019] In one embodiment of the present invention, the method for analyzing an electrode surface is provided, in step (b), in which different colors that are visually distinguishable are matched to the individual regions that were divided in step (a), and the individual regions are materialized and visualized with the matched colors.

[0020] In one embodiment of the present invention, the method for analyzing an electrode surface is provided, in step (c), which quantifies the electrode surface by calculating the proportion of pixels in each individual region included in the electrode surface, based on the total number of pixels of the electrode surface visualized in step (b).

[0021] In one embodiment of the present invention, the hyperspectral CCD provides an electrode surface analysis method for precisely inspecting foreign matter on any specific region included on the electrode surface.

[0022] In one embodiment of the present invention, the field of view (FOV) of the specific region is a region including 0.1 mm to 5 mm in width and 0.1 mm to 5 mm in height, and provides an electrode surface analysis method.

[0023] In one embodiment of the present invention, the electrode is an electrode after an electrode etching process for forming an electrode tab during the electrode manufacturing process, and provides an electrode surface analysis method.

[0024] The present invention also provides a hyperspectral CCD unit that captures an electrode surface using a hyperspectral CCD and obtains a spectrum of the electrode surface; a visualization unit that visualizes the electrode surface using the spectrum of the electrode surface; and a quantification unit that quantifies the visualized electrode surface; and includes an electrode surface analysis system.

Effects of the Invention

[0025] According to the present invention, it is possible to more precisely analyze the type and amount of foreign matter present on the electrode surface after an etching process for forming an electrode tab during the process of manufacturing an electrode of a secondary battery, improving the efficiency of the process and the reliability of the manufactured electrode product. Also, using the advantage of being able to precisely analyze foreign matter, it is possible to inspect the performance of devices used in the etching process, such as an etching laser. [[ID=​​​​​​​This figure shows individual spectra of the current collector surface, the electrode active material layer surface, and foreign matter contained within the negative electrode surface, captured by a hyperspectral CCD. [Figure 3] This figure shows the integrated negative electrode surface spectrum, which is obtained by integrating the individual spectra of the current collector surface, the electrode active material layer surface, and foreign matter contained within the negative electrode surface, as captured by a hyperspectral CCD. [Figure 4] This is a visualization of the negative electrode surface as captured by a hyperspectral CCD. [Figure 5] This figure shows the negative electrode surface visualized through a hyperspectral CCD and a vision camera in Example 1 and Comparative Example 1. [Modes for carrying out the invention]

[0027] The present invention will be described in more detail below to aid in understanding it.

[0028] The terms and words used herein and in the claims are not to be interpreted in a manner limited to their ordinary or dictionary meanings, but rather in a manner consistent with the technical idea of ​​the present invention, based on the principle that inventors may appropriately define the concepts of terms in order to best describe their invention.

[0029] As used herein, the term "electrode surface analysis" means sensing or measuring the materials forming the electrode surface and deriving their types and quantities. In this specification, the electrode subject to electrode surface analysis may be an electrode after the etching process during the electrode manufacturing process. The etching process refers to the process of etching and removing the electrode active material layer in an electrode in which a current collector and electrode active material layer have been formed during the electrode manufacturing process, in order to form an electrode tab. Therefore, after the etching process, the electrode surface may contain the surface of the current collector, the surface of the electrode active material layer, and foreign matter. The foreign matter may be binder that was contained in the electrode active material layer. In short, the electrode surface analysis is for analyzing the types and quantities of foreign matter contained in the electrode surface. Note that the electrode active material layer is formed by coating it on the current collector, and is therefore also called the electrode coating layer.

[0030] Methods for analyzing electrode surfaces The present invention relates to a method for analyzing electrode surfaces.

[0031] The electrode surface analysis method according to the present invention is an electrode surface analysis method that analyzes the electrode surface using a hyperspectral CCD (Charge Coupled Device), (a) A step of taking an image of the electrode surface with a hyperspectral CCD and obtaining the spectrum of the electrode surface; (b) A step of visualizing the electrode surface using the spectrum of the electrode surface; and (c) a step of quantifying the visualized electrode surface;

[0032] In the present invention, in step (a), the electrode surface can be imaged using a hyperspectral CCD to obtain the spectrum of the electrode surface.

[0033] A hyperspectral CCD is a type of camera capable of measuring hyperspectral images (HSI). While RGB images have three channels, HSIs typically measure a wide range of wavelengths, often exceeding 200 bands. Because of this, HSIs can detect complex features not visible in RGB images. While RGB images only possess spatial features, HSIs possess both spectral and spatial features, resulting in superior classification capabilities. Consequently, HSIs can finely classify similar colors and have broad applications in diverse fields, including remote sensing.

[0034] In one embodiment of the present invention, the hyperspectral CCD can be applied to the analysis of the electrode surface to perform a more precise analysis of the electrode surface.

[0035] The hyperspectral CCD includes (i) an optical unit that scans and measures the object to be measured, (ii) a spectroscopic unit that spectrally analyzes the light captured by the optical unit, and (iii) a detection unit that converts the spectrally analyzed light into a spectrum.

[0036] The optical part (i) above includes an optical lens. The optical lens can be used to scan and measure the electrode surface to be measured. Light is captured from the electrode surface through the optical lens. The wavelength of the captured light changes depending on the properties of the electrode surface, the presence, type and amount of foreign matter.

[0037] Furthermore, the (ii) spectroscopic section includes a dispersion element that spectrally separates light.

[0038] Furthermore, the detection unit (iii) is also called the sensor unit and can convert the spectrally separated light into a spectrum.

[0039] In one embodiment of the present invention, the hyperspectral CCD can precisely inspect or measure any specific region contained within the electrode surface.

[0040] The field of view (FOV) of the aforementioned specific region allows for inspection or measurement of a narrow area including a horizontal range of 0.1 mm to 5 mm and a vertical range of 0.1 mm to 5 mm.

[0041] Existing vision cameras have a field of view (FOV) that is limited to a wide area of ​​400mm horizontally and 400mm vertically, resulting in poor accuracy. Thus, existing vision cameras have a large FOV, making it difficult to precisely analyze the type and amount of foreign matter remaining on the electrode surface, as they can only detect the presence or absence of such material.

[0042] In one embodiment of the present invention, a threshold for distinguishing constituent components present on the electrode surface can be determined by utilizing the spectrum of the electrode surface obtained from the hyperspectral CCD. In this case, the constituent components present on the electrode surface include the surface of the current collector, the surface of the electrode active material layer, and foreign matter.

[0043] For example, the spectrum of the electrode surface obtained from the hyperspectral CCD may include individual spectra for the surface of the current collector, the surface of the electrode active material layer, and foreign matter contained within the electrode surface. The individual spectra are superimposed to obtain an integrated spectrum. A discrimination criterion is set in the integrated spectrum, which is the boundary value that distinguishes the surface of the current collector, the surface of the electrode active material layer, and foreign matter. At this time, the spectrum shows the correlation between wavelength and intensity of brightness.

[0044] The aforementioned criteria can be set by logic including (i) and (ii) below: (i) In the spectrum of the electrode surface obtained from the hyperspectral CCD, the step of selecting the wavelength region in which the brightness gap (gap) between two types selected from the group consisting of the surface of the current collector, the surface of the electrode active material layer, and foreign matter contained in the electrode surface is the largest; and (ii) A step in which the average or median value of the luminance corresponding to the wavelength region with the largest luminance gap between the individual regions is selected as the discrimination criterion.

[0045] Specifically, the gap may include (a) a brightness gap between the surface of the current collector and the surface of the electrode active material layer; (b) a brightness gap between the surface of the electrode active material layer and foreign matter; and (c) a brightness gap between the surface of the current collector and foreign matter.

[0046] In one embodiment of the present invention, individual regions of the electrode surface can be divided based on the discrimination criteria. For example, the individual regions divided on the electrode surface may include the surface of the current collector, the surface of the electrode active material layer, and foreign matter.

[0047] In the present invention, in step (b), the electrode surface can be visualized by utilizing the spectrum of the electrode surface.

[0048] In the stage described in (a) above, different colors that visually distinguish the individual regions can be matched. In this case, the matching colors are not fixed to any particular color, but are not particularly limited as long as these individual regions are visually distinguishable by different colors.

[0049] Here, "visualization" means representing individual regions of the electrode surface, each matched with a different color, with the matched color. The visualization can be represented by a visualization software program, and is not particularly limited as long as it is a software program driven by logic that can represent each individual region of the electrode surface, separated by a discrimination criterion, with the matched color.

[0050] In the present invention, in step (c), the visualized electrode surface can be quantified.

[0051] Specifically, the electrode surface can be quantified by calculating the proportion of pixels in each individual region based on the total number of pixels on the visualized electrode surface. In particular, the proportion of pixels contained in the individual region corresponding to the divided foreign matter can be calculated to obtain the amount of each foreign matter remaining on the electrode surface.

[0052] The quantification is performed by a quantification software program, and is not particularly limited as long as the software program is driven by logic that calculates the proportion of pixels corresponding to each component based on the total number of pixels on the electrode surface.

[0053] Electrode surface analysis system The present invention also relates to an analysis system for electrode surfaces.

[0054] The electrode surface analysis system according to the present invention includes a hyperspectral CCD unit for capturing images of the electrode surface; a visualization unit for visualizing the electrode surface using the spectrum of the electrode surface captured by the hyperspectral CCD; and a quantification unit for quantifying the visualized electrode surface.

[0055] The hyperspectral CCD section may include a hyperspectral CCD.

[0056] Furthermore, the visualization unit may include a visualization software program, and is not particularly limited as long as it is a software program driven by logic that represents the regions of each component separated on the electrode surface by discrimination criteria with matched colors.

[0057] Furthermore, the quantification unit may include a quantification software program, and is not particularly limited as long as it is a software program driven by logic that calculates the proportion of pixels corresponding to each constituent component based on the entire electrode surface pixel.

[0058] The following are preferred embodiments to aid in understanding the present invention. However, these embodiments are merely illustrative of the present invention, and it will be obvious to those skilled in the art that various changes and modifications are possible within the scope of the present invention and the technical concept, and such changes and modifications will naturally fall within the scope of the attached claims.

[0059] Example 1 Since the correlation between wavelength and brightness can be obtained from images captured by a hyperspectral CCD (Figure 1), the spectrum of the negative electrode surface was secured and analyzed using this property as shown below. In this case, the correlation between wavelength and brightness is also called the spectrum of the pixel.

[0060] (1) Spectrum acquisition for the negative electrode surface A hyperspectral CCD (Mitutoyo) was used to photograph the electrode surface after the etching process for forming electrode tabs during the electrode manufacturing process. The electrode, as the negative electrode, includes a Cu current collector and a negative electrode active material layer formed on one surface of the Cu current collector. The surface of the negative electrode includes the surface of the Cu current collector ("Bare foil"), a binder separated from the negative electrode active material layer ("Binder Residue"), and the negative electrode active material layer ("Coating").

[0061] Individual spectra were obtained for the bare foil, binder resin, and coating from images of the negative electrode surface captured by the hyperspectral CCD (Figure 2). These individual spectra were realized as boxplot spectra by securing raw data extracted from the hyperspectral CCD images. The microscope images were taken with an optical microscope, and the single-wavelength images were taken with a single-wavelength spectrophotometer.

[0062] (2) Establishment of classification criteria for foreign matter on the negative electrode surface After obtaining an integrated spectrum by combining the individual spectra of the bare foil, binder resin, and coating, the discrimination thresholds (thresholds) at which each individual spectrum is separated in the integrated spectrum were selected as follows (Figure 3).

[0063] In the integrated spectrum shown in Figure 3, the wavelength region with the largest brightness gap between each individual spectrum was selected. First, region A was selected as the wavelength region with the largest brightness gap between Coating and Binder, and region B was selected as the wavelength region with the largest brightness gap between Binder and Bare foil. The wavelength range of region A is 708-754 nm, and the wavelength range of region B is 502-548 nm.

[0064] The average value of the luminance corresponding to the wavelength region corresponding to area A was used as discrimination criterion A, and the average value of the luminance corresponding to the wavelength region corresponding to area B was used as discrimination criterion B.

[0065] The negative electrode surface was classified using the aforementioned discrimination criteria A and B.

[0066] Table 1 below is a classification table of negative electrode surfaces classified using the aforementioned discrimination criteria A and B. The negative electrode surfaces were divided into four cases that can be derived using discrimination criteria A and B, and the negative electrode surfaces were classified into individual regions corresponding to these cases.

[0067] [Table 1]

[0068] As shown in Table 1 above, each individual region included in the negative electrode surface and the color to which it is matched can be defined based on the discrimination criteria A and B. The color is not particularly limited as long as it is a color that can visually distinguish the negative electrode surface divided by discrimination criteria A and B.

[0069] (3) Visualization of the negative electrode surface The negative electrode surface was visualized using the individual regions defined by the aforementioned discrimination criteria A and B, and the corresponding colors (Figure 4). This visualization was performed using a software program driven by a logic that could represent the object of visualization, i.e., the individual regions, with specific colors.

[0070] (4) Quantification of the negative electrode surface The quantification method involved measuring the number of pixels corresponding to Bare foil, Binder Residue, and Coating on the visualized negative electrode surface, and then calculating the proportion of each corresponding pixel within the total number of pixels on the negative electrode surface. This quantification was performed using a software program driven by logic capable of calculating the proportion of pixels in a specific region (i.e., an individual region) relative to the total number of pixels on the negative electrode surface.

[0071] Table 2 below quantifies the negative electrode surface, including the individual regions of Bare foil, Binder, and Coating.

[0072] [Table 2]

[0073] As shown in Table 2 above, the amount of residual binder, which is a foreign substance on the negative electrode surface, can be determined.

[0074] Comparative Example 1 A vision camera was used instead of a hyperspectral CCD to analyze the negative electrode surface.

[0075] As a result, as shown in Figure 5, it was only possible to confirm the extent to which foreign matter was present on the negative electrode surface, and further detailed analysis could not be performed.

[0076] Although the present invention has been described above with reference to limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and that various modifications and variations are possible within the same scope as the technical concept of the present invention and the claims described below by persons with ordinary skill in the art to which the present invention pertains.

Claims

1. A method for analyzing electrode surfaces using a hyperspectral CCD (charge-coupled device), (a) A step of taking an image of the electrode surface with a hyperspectral CCD and obtaining the spectrum of the electrode surface, (b) A step of visualizing the electrode surface using the spectrum of the electrode surface, and (c) A method for analyzing an electrode surface, comprising the step of quantifying the visualized electrode surface.

2. In step (a) above, in the spectrum showing the correlation between wavelength and brightness of the electrode surface captured by the hyperspectral CCD, After selecting the average or median brightness value corresponding to the wavelength region where the gap between two types selected from the group consisting of the surface of the current collector, the surface of the electrode active material layer, and foreign matter contained in the electrode surface is large, as the discrimination criterion, The method for analyzing the electrode surface according to claim 1, wherein the electrode surface is divided into the surface of the current collector, the surface of the electrode active material layer, and individual regions including foreign matter, based on the aforementioned discrimination criteria.

3. The method for analyzing an electrode surface according to claim 1, wherein in step (b), different colors that are visually distinguishable are matched to the individual regions that were divided in step (a), and the individual regions are materialized and visualized with the matched colors.

4. The method for analyzing an electrode surface according to claim 1, wherein in step (c), the electrode surface is quantified by calculating the proportion of pixels in each individual region included in the electrode surface based on the total number of pixels of the electrode surface visualized in step (b).

5. The method for analyzing an electrode surface according to claim 1, wherein the hyperspectral CCD precisely inspects for foreign matter in any specific region contained within the electrode surface.

6. The method for analyzing the electrode surface according to claim 5, wherein the field of view (FOV) of the specified region is a region including a width of 0.1 mm to 5 mm and a height of 0.1 mm to 5 mm.

7. The method for analyzing the surface of an electrode according to claim 1, wherein the electrode is an electrode after an electrode etching process in which an electrode tab is formed during the electrode manufacturing process.

8. A hyperspectral CCD (charge-coupled device) is used to image the electrode surface and obtain the spectrum of the electrode surface. A visualization unit that visualizes the electrode surface using the spectrum of the electrode surface, and An electrode surface analysis system including a quantification unit for quantifying the visualized electrode surface.

Images