Electrode surface analysis method and electrode surface analysis system

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 capable of improving the process efficiency and the product reliability by precisely analyzing foreign substances remaining on an electrode surface during an electrode manufacturing process, by using a hyperspectral CCD.

Description

Electrode surface analysis method and electrode surface analysis system

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority from Korean Patent Application No. 10-2024-0041537, dated March 27, 2024, the entire contents of which are incorporated herein by reference.

[0003] Technology field

[0004] The present invention relates to an electrode surface analysis method and an electrode surface analysis system for precisely analyzing foreign substances on an electrode surface, for analyzing an electrode surface during a secondary battery manufacturing process.

[0005] As technological development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing, and accordingly, extensive research is being conducted on secondary batteries that can meet various needs.

[0006] These secondary batteries are manufactured by having an electrode assembly housed in a battery case together with an electrolyte. These electrode assemblies are categorized into stacked, folded, and stack-folded types, depending on the manufacturing method. Stacked or stack-folded electrode assemblies have a structure in which the unit assemblies are sequentially stacked, with a separator between the positive and negative electrodes. To manufacture these electrode assemblies, it is necessary to first manufacture positive and negative electrodes with electrode tabs formed thereon.

[0007] The electrode process for manufacturing electrodes of secondary batteries 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 as in-line processes.

[0008] The above (1) mixing process is a process for preparing a slurry for forming an active material layer of an electrode. The slurry can be prepared by measuring and mixing various raw materials necessary for forming the active material layer, including electrode active materials, binders, and conductive materials.

[0009] In addition, the above (2) coating process is a process of forming an electrode active material layer by thinly coating the slurry on a current collector and drying it. The current collector and the electrode active material layer formed on the current collector are referred to as an electrode sheet.

[0010] In addition, the above (3) rolling process is a process of uniformly stretching the electrode sheet by passing it between two rolls. The above rolling process is also called a roll pressing process.

[0011] In addition, the above (4) slitting and notching process is a process for cutting the electrode sheet according to the battery size. The slitting process can cut the battery sheet vertically according to the battery design specifications. The notching process is a process for forming a V-groove and an electrode tab after the slitting process. At this time, in the 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 tab can be formed by etching. Meanwhile, in a small pouch line, an etching process may be performed between the rolling process and the slitting process.

[0012] However, foreign substances generated during this etching process can remain on the electrode surface, potentially degrading its quality. If the type and amount of foreign substances remaining on the electrode surface could be identified, the etching process could be designed and implemented to minimize their generation. Here, the foreign substances may refer to residues such as binder contained in the electrode's active material layer.

[0013] Typically, vision systems installed in inline equipment for inline electrode manufacturing processes are used to detect residual foreign matter. However, vision systems typically have a large field of view (FOV), making it difficult to determine the specific type and amount of residual foreign matter. The electrode etching process is performed inline, and the limitations of inline equipment necessitate the installation of vision systems. Furthermore, installing cameras capable of more precise foreign matter analysis beyond vision systems presents technical challenges.

[0014] Therefore, it is necessary to develop a technology for an electrode surface analysis method that can identify the type and amount of foreign substances remaining on the electrode surface after the electrode etching process.

[0015] [Prior Art Literature]

[0016] (Patent Document 1) Korean Patent Publication No. 2011-0029011

[0017] The inventors of the present invention have conducted multifaceted research to solve the above problems and have confirmed that by introducing a hyperspectral CCD (Charge Coupled Device) as offline equipment in addition to the vision, which is an inline equipment equipped in the inline process for manufacturing electrodes, the electrode surface can be analyzed more precisely.

[0018] Accordingly, the purpose of the present invention is to provide a method for analyzing an electrode surface using a hyperspectral CCD.

[0019] In addition, another object of the present invention is to provide an electrode surface analysis system using a hyperspectral CCD.

[0020] In order to achieve the above purpose, the present invention provides an electrode surface analysis method that analyzes an electrode surface using a hyperspectral CCD (Charge Coupled Device),

[0021] (a) A step of photographing an electrode surface with a hyperspectral CCD to obtain a spectrum of the electrode surface;

[0022] (b) a step of visualizing the electrode surface using the spectrum of the electrode surface; and

[0023] (c) A method for analyzing an electrode surface, including a step of quantifying the above visualized electrode surface, is provided.

[0024] In one embodiment of the present invention, in the step (a), in the spectrum showing the correlation between the wavelength and the intensity of brightness of the electrode surface photographed by the hyperspectral CCD,

[0025] After selecting the average value or median value of luminosity corresponding to a wavelength region with a large gap in luminosity between two types selected from the group consisting of the surface of the current collector included in the electrode surface, the surface of the electrode active material layer, and foreign substances, as a discrimination criterion,

[0026] Based on the above discrimination criteria, a method for analyzing an electrode surface is provided, which divides the electrode surface into individual regions including the surface of a current collector, the surface of an electrode active material layer, and foreign substances.

[0027] In one embodiment of the present invention, in step (b), a method for analyzing an electrode surface is provided, wherein visually distinct colors are matched for the individual areas distinguished in step (a), and the individual areas are visualized by implementing them with the matched colors.

[0028] In one embodiment of the present invention, in step (c), a method for analyzing an electrode surface is provided, wherein the electrode surface is quantified by calculating the ratio of pixels of each individual area included in the electrode surface based on the total pixels of the electrode surface visualized in step (b).

[0029] In one embodiment of the present invention, the hyperspectral CCD provides an electrode surface analysis method for precisely inspecting foreign substances in any specific area included in the electrode surface.

[0030] In one embodiment of the present invention, a method for analyzing an electrode surface is provided, wherein the field of view (FOV) of the specific region is an region including a width of 0.1 mm to 5 mm and a length of 0.1 mm to 5 mm.

[0031] In one embodiment of the present invention, a method for analyzing an electrode surface is provided, wherein the electrode is an electrode after an electrode etching process for forming an electrode tab during an electrode manufacturing process.

[0032]

[0033] The present invention also comprises a hyperspectral CCD unit that photographs an electrode surface using a hyperspectral CCD to obtain a spectrum of the electrode surface;

[0034] A visualization unit that visualizes the electrode surface using the spectrum of the electrode surface; and

[0035] An electrode surface analysis system is provided, including a quantification unit for quantifying the above-mentioned visualized electrode surface.

[0036] According to the present invention, the type and amount of foreign substances present on the electrode surface after the etching process for forming electrode tabs during the manufacturing process of secondary battery electrodes can be more precisely analyzed, thereby improving process efficiency and product reliability of the manufactured electrode. Furthermore, the advantage of being able to precisely analyze foreign substances can be utilized to check the performance of equipment used in the etching process, such as an etching laser.

[0037] Figure 1 shows data on the correlation between wavelength and intensity of brightness that can be obtained from images captured with a hyperspectral CCD.

[0038] Figure 2 shows individual spectra for the current collector surface, electrode active material layer surface, and foreign substances contained in the cathode surface, captured by a hyperspectral CCD.

[0039] Figure 3 shows an integrated spectrum of the cathode surface, which integrates individual spectra for the current collector surface, electrode active material layer surface, and foreign substances included in the cathode surface, captured by a hyperspectral CCD.

[0040] Figure 4 visualizes the cathode surface photographed with a hyperspectral CCD.

[0041] Figure 5 shows the cathode surface visualized using a hyperspectral CCD and a vision camera in Example 1 and Comparative Example 1.

[0042] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0043] The terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0044] The term “electrode surface analysis” as used herein refers to detecting or measuring materials forming the electrode surface to derive their types and amounts. In this specification, the electrode subject to electrode surface analysis may be an electrode after an etching process during the electrode manufacturing process. The etching process refers to a process of etching and removing the electrode active material layer from an electrode on which a current collector and an electrode active material layer are formed during the electrode manufacturing process in order to form an electrode tab. Therefore, the electrode surface after the etching process may include the current collector surface, the electrode active material layer surface, and foreign substances. The foreign substances may be binders included in the electrode active material layer. Ultimately, the electrode surface analysis may be for analyzing the types and amounts of foreign substances included in the electrode surface. In this case, since the electrode active material layer is formed by being coated on a current collector, it may also be referred to as an electrode coating layer.

[0045]

[0046] Electrode surface analysis method

[0047] The present invention relates to a method for analyzing an electrode surface.

[0048] 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),

[0049] (a) a step of photographing an electrode surface with a hyperspectral CCD to obtain a spectrum of the electrode surface;

[0050] (b) a step of visualizing the electrode surface using the spectrum of the electrode surface; and

[0051] (c) a step of quantifying the visualized electrode surface;

[0052]

[0053] In the present invention, in the step (a), the electrode surface is photographed using a hyperspectral CCD, thereby obtaining the spectrum of the electrode surface.

[0054]

[0055] A hyperspectral CCD is a type of camera capable of capturing hyperspectral images (HSI). While RGB has three channels, HSI measures a wide range of wavelengths, sometimes exceeding 200 bands. To achieve this, HSI detects complex features not found in RGB images. While RGB images have only spatial features, HSI possesses both spectral and spatial features, demonstrating superior classification performance. Therefore, HSI can precisely classify even similar colors, making it widely applicable to various fields, including remote sensing.

[0056]

[0057] In one embodiment of the present invention, the hyperspectral CCD is applied to electrode surface analysis, so that the electrode surface can be analyzed more precisely.

[0058] The above hyperspectral CCD includes (i) an optical section that scans and measures a measurement target, (ii) a spectroscopic section that spectroscopically analyzes light received by the optical section, and (iii) a detector that converts the spectroscopic light into a spectrum.

[0059] The above (i) optical section includes an optical lens. Using the optical lens, the electrode surface, which is the measurement target, can be scanned and measured. Light is received from the electrode surface through the optical lens. The wavelength of the light received may vary depending on the properties of the electrode surface, the presence or absence of foreign substances, and their type and amount.

[0060] Additionally, the above (ii) spectroscopic unit includes a dispersive element that disperses light.

[0061] In addition, the above (iii) detection unit is also called a sensor unit and can convert the dispersed light into a spectrum.

[0062]

[0063] In one embodiment of the present invention, the hyperspectral CCD can precisely inspect or measure any specific area included in the electrode surface.

[0064] The field of view (FOV) of the above specific area enables inspection or measurement of a narrow area including 0.1 mm to 5 mm in width and 0.1 mm to 5 mm in height.

[0065] Existing vision cameras have a field of view (FOV) that can only inspect or measure a wide area (400 mm wide and 400 mm high), resulting in poor accuracy. This large field of view (FOV) allows for only a cursory inspection of the presence of residual foreign matter on the electrode surface, making precise analysis of the type and amount of foreign matter difficult.

[0066]

[0067] In one embodiment of the present invention, a threshold for distinguishing components present on the electrode surface can be obtained using the spectrum of the electrode surface obtained from the hyperspectral CCD. In this case, the components present on the electrode surface may include the surface of the current collector, the surface of the electrode active material layer, and foreign substances.

[0068] 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 substances included in the electrode surface. The individual spectra are superimposed to obtain an integrated spectrum. In the integrated spectrum, a discrimination criterion, which is a boundary value for distinguishing the surface of the current collector, the surface of the electrode active material layer, and foreign substances, is set. At this time, the spectrum may represent a correlation between wavelength and intensity of brightness.

[0069] The above discrimination criteria can be set by logic including the following (i) and (ii):

[0070] (i) a step of selecting a wavelength region in which the gap in luminosity between two selected from the group consisting of the surface of the current collector included in the electrode surface, the surface of the electrode active material layer, and foreign substances is the largest in the spectrum of the electrode surface obtained from a hyperspectral CCD; and

[0071] (ii) A step of selecting the average or median value of the luminosity corresponding to the wavelength region with the largest gap in luminosity between the individual zones as a discrimination criterion.

[0072] Specifically, the gap may include (a) a gap in luminosity between the surface of the current collector and the surface of the electrode active material layer; (b) a gap in luminosity between the surface of the electrode active material layer and a foreign substance; and (c) a gap in luminosity between the surface of the current collector and a foreign substance.

[0073]

[0074] In one embodiment of the present invention, individual regions of the electrode surface can be distinguished based on the above discrimination criteria. For example, the individual regions distinguished on the electrode surface may include the surface of the current collector, the surface of the electrode active material layer, and foreign substances.

[0075]

[0076] In the present invention, in the step (b), the electrode surface can be visualized using the spectrum of the electrode surface.

[0077] Different visually distinct colors can be matched to the individual areas identified in step (a) above. The matching colors are not limited to specific colors, and are not particularly limited as long as the individual areas are visually distinct colors.

[0078] Here, the visualization refers to implementing individual areas of the electrode surface, each of which is matched with a different color, with the matching color. The visualization can be implemented using a visualization software program, and is not particularly limited as long as it is a software program driven by logic capable of implementing each individual area on the electrode surface, distinguished by a discrimination criterion, with the matching color.

[0079]

[0080] In the present invention, in the step (c), the visualized electrode surface can be quantified.

[0081] Specifically, the electrode surface can be quantified by calculating the ratio of pixels corresponding to each individual zone based on the total pixels of the visualized electrode surface. In particular, the amount of each foreign substance remaining on the electrode surface can be obtained by calculating the ratio of pixels included in the individual zones corresponding to the identified foreign substances.

[0082] The above quantification can be performed by a quantification software program, and is not particularly limited as long as it is a software program driven by logic that calculates the ratio of pixels corresponding to each component based on the entire pixels of the electrode surface.

[0083]

[0084] Electrode Surface Analysis System

[0085] The present invention also relates to an electrode surface analysis system.

[0086] An electrode surface analysis system according to the present invention comprises: a hyperspectral CCD unit for photographing an electrode surface; a visualization unit for visualizing the electrode surface using a spectrum of the electrode surface photographed by the hyperspectral CCD; and a quantification unit for quantifying the visualized electrode surface.

[0087] The above hyperspectral CCD unit may include a hyperspectral CCD.

[0088] In addition, 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 can implement the area of ​​each component distinguished by a discrimination criterion on the electrode surface with a matching color.

[0089] In addition, 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 ratio of pixels corresponding to each component based on the entire pixels of the electrode surface.

[0090] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0091]

[0092] Example 1

[0093] Since the correlation between wavelength and intensity of brightness can be obtained from an image captured by a hyperspectral CCD (Fig. 1), the spectrum of the cathode surface was obtained and analyzed as shown below using this. At this time, the correlation between wavelength and intensity of brightness is also called the spectrum of pixels.

[0094]

[0095] (1) Acquisition of spectrum for the cathode surface

[0096] Using a hyperspectral CCD (Hyper Spectral Camera, Mitutoyo Corporation), the surface of the electrode after the etching process for forming an electrode tab during the electrode manufacturing process was photographed. The electrode is a negative electrode and 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 a negative electrode active material layer (coating).

[0097] From the cathode surface images captured by the hyperspectral CCD, individual spectra were obtained for the bare foil, binder residue, and coating (Fig. 2). The individual spectra were implemented as boxplot spectra by securing raw data extracted from the hyperspectral CCD images. The microscope images were captured using an optical microscope, and the single wavelength images were captured using a single wavelength spectrophotometer.

[0098]

[0099] (2) Establishment of classification criteria for foreign substances on the cathode surface

[0100] After obtaining an integrated spectrum by integrating the individual spectra of the Bare Foil, Binder Residue, and Coating, the threshold for distinguishing each individual spectrum from the integrated spectrum was selected as follows (Fig. 3).

[0101] In the integrated spectrum shown in Fig. 3, the wavelength region with the largest gap in luminosity between each individual spectrum was selected. First, region A was selected as the wavelength region with the largest gap in luminosity between the coating and the binder, and region B was selected as the wavelength region with the largest gap in luminosity between the binder and the bare foil. The wavelength region of region A is 708 to 754 nm, and the wavelength region of region B is 502 to 548 nm.

[0102] The average value of the luminosity corresponding to the wavelength region corresponding to the above region A is referred to as discrimination criterion A, and the average value of the luminosity corresponding to the wavelength region corresponding to the above region B is referred to as discrimination criterion B.

[0103]

[0104] Using the above discrimination criteria A and discrimination criteria B, the cathode surface was classified.

[0105] Table 1 below is a classification table of cathode surfaces classified using the above discrimination criteria A and discrimination criteria B. The cathode surfaces were classified into individual areas corresponding to the four cases that can be derived using discrimination criteria A and discrimination criteria B.

[0106]

[0107] Classification Criteria A Criteria B Cathode Surface Classification Color Note Case 1> Criteria A> Criteria BB Are foil Case 2 < Discrimination Criterion A > Discrimination Criterion BCoating Estimated as Coating (Reliability of Discrimination Criterion B is lower than that of Discrimination Criterion A) Case 3> Discrimination Criterion A < Discrimination Criterion BBinder Case 4< Discrimination Criterion A< Discrimination Criterion BCoating

[0108]

[0109] As shown in Table 1 above, based on the discrimination criteria A and B, each individual area included in the cathode surface and its matching color can be specified. The color is not particularly limited as long as it is a color that can visually distinguish the cathode surface classified by the discrimination criteria A and B.

[0110]

[0111] (3) Visualization of the cathode surface

[0112] The cathode surface, including individual zones distinguished by the above-mentioned discrimination criteria A and B, and the corresponding colors were used to visualize the cathode surface (Fig. 4). At this time, the visualization was performed using a software program driven by logic capable of expressing the visualization target, i.e., the individual zones, in specific colors.

[0113]

[0114] (4) Quantification of the cathode surface

[0115] The quantification method measured the number of pixels corresponding to Bare Foil, Binder Residue, and Coating on the visualized cathode surface, and then calculated the ratio included in the total number of pixels on the cathode surface. At this time, the quantification was performed using a software program driven by logic capable of calculating the ratio of pixels corresponding to a specific area included in the quantification target, i.e., an individual area, to the total number of pixels on the cathode surface, i.e., the target of quantification.

[0116] Table 2 below quantifies the cathode surface including individual areas: Bare foil, Binder, and Coating.

[0117]

[0118] Pixel quantity(number)Ratio(%)Bare foil18,5855.9Binder164,67452.4Coating131,10941.7Total314,368100.0

[0119]

[0120] As shown in Table 2 above, the residual amount of Binder, a foreign substance on the cathode surface, can be known.

[0121]

[0122] Comparative Example 1

[0123] The cathode surface was analyzed using a vision camera instead of a hyperspectral CCD.

[0124] As a result, as shown in Fig. 5, only the extent to which foreign substances existed on the cathode surface could be confirmed, and further precise analysis could not be performed.

[0125]

[0126] Although the present invention has been described above with reference to limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical idea of ​​the present invention and the equivalent scope of the patent claims to be described below by a person having ordinary skill in the art to which the present invention pertains.

Claims

1. An electrode surface analysis method that analyzes the electrode surface using a hyperspectral CCD (Charge Coupled Device). (a) A step of photographing an electrode surface with a hyperspectral CCD to obtain a 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: a step of quantifying the visualized electrode surface; 2. In paragraph 1, In the above step (a), in the spectrum showing the correlation between the wavelength and intensity of brightness of the electrode surface captured by the hyperspectral CCD, After selecting the average value or median value of luminosity corresponding to a wavelength range with a large gap between two types selected from the group consisting of the surface of the current collector included in the electrode surface, the surface of the electrode active material layer, and foreign substances, as a discrimination criterion, An electrode surface analysis method, which divides the electrode surface into individual regions including the surface of a current collector, the surface of an electrode active material layer, and foreign substances based on the above discrimination criteria.

3. In paragraph 1, In the step (b), a method for analyzing an electrode surface is provided, wherein different visually distinct colors are matched for the individual areas distinguished in the step (a), and the individual areas are visualized by implementing them with the matched colors.

4. In paragraph 1, An electrode surface analysis method in which, in step (c), the electrode surface is quantified by calculating the ratio of pixels of each individual area included in the electrode surface based on the total pixels of the electrode surface visualized in step (b).

5. In paragraph 1, The above hyperspectral CCD is a method for analyzing an electrode surface, which precisely inspects any specific area included in the electrode surface for foreign substances.

6. In paragraph 5, A method for analyzing an electrode surface, wherein the field of view (FOV) of the above specific area is an area including 0.1 mm to 5 mm in width and 0.1 mm to 5 mm in height.

7. In paragraph 1, A method for analyzing an electrode surface, wherein the above electrode is an electrode after an electrode etching process for forming an electrode tab during an electrode manufacturing process.

8. A hyperspectral CCD section that photographs the electrode surface using a hyperspectral CCD to obtain a 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 that quantifies the above-mentioned visualized electrode surface.

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