Analysis system and analysis method for foreign matter in positive electrode material

Abstract

The present invention relates to an analysis system and an analysis method for foreign matters in a positive electrode material, and the analysis system for foreign matters in a positive electrode material according to the present invention comprises: a pretreatment unit for preparing a single-layer sample of a positive electrode material powder; the measuring unit is used for obtaining an optical image of the single-layer sample by using an optical microscope; and an analysis unit that analyzes the optical image of the single-layer sample, thereby obtaining information on the foreign matter in the positive electrode material.

Description

Technical Field

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0085370, filed on June 30, 2023, which is hereby incorporated by reference in its entirety.

[0002] The present invention relates to a system and method for analyzing foreign matter in a positive electrode material, and more particularly, to a system and method for analyzing foreign matter in a positive electrode material that can quantitatively analyze the shape and composition of foreign matter that may cause low voltage in the positive electrode material. Background Art

[0003] The production of lithium-ion batteries involves a variety of manufacturing processes, each with its own potential for defects that can affect battery performance. Defects caused by foreign matter mixed into raw materials are particularly frequent and incur significant quality-related costs, as they can force finished batteries to be scrapped. Furthermore, even when equipment is functioning properly, there's still the risk of receiving raw materials from suppliers contaminated with foreign matter, making effective detection methods essential.

[0004] The types of defects caused by mixed foreign matter vary depending on their physical properties and size. For example, large foreign matter may tear the separator during the rolling process, resulting in a short circuit defect caused by direct contact between the positive and negative electrodes. In addition, non-conductive foreign matter can increase the internal resistance, thereby reducing the maximum output. However, defects caused by such foreign matter can be detected relatively easily during the activation process. On the other hand, upon repeated charge / discharge cycles, metallic foreign matter within the positive electrode material can be ionized in the electrolyte, undergoing processes such as recrystallization in the pores of the separator or on the negative electrode, which makes it difficult to detect defects immediately. Therefore, during the storage of the battery before shipment, recrystallized foreign matter may cause low voltage defects, which lead to significant voltage drops and increased self-discharge rates.

[0005] Conventionally, methods such as inductively coupled plasma (ICP) or X-ray fluorescence (XRF) have been used to detect metallic foreign matter in cathode materials. However, while ICP-AES offers the advantage of detecting trace foreign matter at the ppm level, it has difficulty determining the shape of the foreign matter, making it difficult to identify the source of contamination. Even when using active materials that have passed quality inspections, such as those documented in a Certificate of Analysis (COA), low voltage issues can still occur. Meanwhile, XRF allows for analysis of large quantities of active material, but struggles to detect foreign matter smaller than a certain size (<40 μm).

[0006] Recently, an inspection method using scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) has been tried, which can confirm the shape and composition of foreign matter and detect fine particles. However, since measuring a large area requires a lot of time, this method has the disadvantage of being difficult to apply to industrial applications.

[0007] Therefore, a new method of analyzing foreign matter in a positive electrode material is required, which can detect the shape and composition of metallic foreign matter having a size of about 40 μm or less in a short time. Summary of the Invention

[0008] Technical issues

[0009] The present invention has been made in order to solve the above problems, and an object of the present invention is to provide a system and method for analyzing foreign matter in positive electrode materials, which can quickly detect the shape and composition of fine metal foreign matter present in positive electrode material powder.

[0010] Means of solving the problem

[0011] According to one aspect of the present invention, a system for analyzing metal foreign matter in a positive electrode material is provided, the system comprising: a pretreatment unit configured to prepare a single-layer sample of positive electrode material powder; a measuring unit configured to obtain an optical image of the single-layer sample using an optical microscope; and an analysis unit configured to analyze the optical image of the single-layer sample to obtain information about foreign matter in the positive electrode material; wherein the pretreatment unit comprises a substrate and a first component, the positive electrode material powder is coated on the substrate, and the first component is configured to remove a portion of the positive electrode material powder coated on the substrate to allow positive electrode material particles to be distributed in a single layer.

[0012] According to another aspect of the present invention, a method for analyzing metal foreign matter in a positive electrode material is provided, the method comprising: a first process in which positive electrode material powder is coated on a substrate and a portion of the coated positive electrode material powder is removed to produce a single-layer sample; a second process in which an optical image of the single-layer sample is obtained using an optical microscope; and a third process in which the optical image of the single-layer sample is analyzed to obtain information about the foreign matter in the positive electrode material.

[0013] According to another aspect of the present invention, an optical microscope is provided, which includes: a light source; a CCD camera, which is arranged below the light source and configured to capture an optical image of a sample; a lens portion, which is arranged below the CCD camera and configured to magnify the image of the sample; a mounting portion, which is arranged below the lens portion and on which the sample is placed; a driving portion, which is configured to move the mounting portion and the lens portion; and a polarizing portion, which is arranged between the light source and the CCD camera to eliminate diffusely reflected light from the sample.

[0014] Beneficial effects

[0015] The system and method for analyzing metallic foreign matter in a positive electrode material according to the present invention may involve detecting metallic foreign matter that differs in color and brightness from the positive electrode active material by analyzing an optical image obtained using an optical microscope. When utilizing the system and method of the present invention, shape information of metallic foreign matter having a size of approximately 40 μm or less can be obtained in a shorter time than with conventional methods.

[0016] In addition, when a laser light source is attached to an optical microscope, the detected metallic foreign matter can be irradiated with laser light to analyze the line spectra emitted during their destruction, and composition information of the metallic foreign matter can also be obtained.

[0017] Thus, using the system and method for analyzing metallic foreign matter in cathode materials according to the present invention, it is possible to obtain information on the shape and composition of metallic foreign matter within the cathode material, which cannot be analyzed using conventional methods. This allows for more efficient management of foreign matter within the cathode material, thereby suppressing defects such as low voltage phenomena. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 : is a view showing a process of manufacturing a single-layer sample according to the first embodiment of the present invention.

[0019] Figure 2 : is a view showing a process of manufacturing a single-layer sample according to the second embodiment of the present invention.

[0020] Figure 3 are views showing differences in optical images according to light source irradiation methods of an optical microscope.

[0021] Figure 4 is a diagram showing spectrum data according to a light source irradiation method of an optical microscope.

[0022] Figure 5 : are views showing the difference in optical images depending on the presence or absence of a polarizing section in an optical microscope.

[0023] Figure 6 is a diagram showing the result of detecting metallic foreign matter according to the present invention.

[0024] Figure 7 are views showing optical images of a sample manufactured using a stretchable substrate and a sample manufactured using a carbon ribbon.

[0025] Figure 8 are views showing an optical image (A) of a sample manufactured by applying positive electrode material powder onto an adhesive substrate and then removing upper layer particles using a delaminating member, and an optical image (B) of a sample manufactured by applying positive electrode material powder onto an adhesive substrate without undergoing a particle removal process using a delaminating member.

[0026] Figure 9 : is a diagram showing the results of analyzing the composition of metallic foreign matter using laser light.

[0027] Figure 10 is a view showing the structure of an optical microscope according to the present invention. DETAILED DESCRIPTION

[0028] Hereinafter, the present invention will be described in detail.

[0029] Analysis System

[0030] First, a system for analyzing metallic foreign matter in a positive electrode material according to the present invention will be described.

[0031] An analysis system according to the present invention is provided to analyze metallic foreign matter contained in a positive electrode material, and includes (1) a pre-processing section, (2) a measuring section, and (3) an analyzing section.

[0032] The type of the positive electrode material powder as the object to be measured is not particularly limited, and may be various types of positive electrode material powders used in the field of secondary batteries. The positive electrode material powder may include metallic foreign matter and positive electrode active material particles.

[0033] The type of metallic foreign matter contained in the positive electrode material powder is not particularly limited, and may include various metallic foreign matter that may be mixed during the positive electrode material manufacturing process. For example, the metallic foreign matter may include one or more materials selected from the group consisting of Fe, Cr, Cu, and Zn, but is not limited thereto.

[0034] The type of positive electrode active material particles contained in the positive electrode material powder is not particularly limited, and may be positive electrode active material particles commonly used in the field of secondary battery technology. For example, the positive electrode active material particles may be lithium metal oxides including one or more metal elements selected from the group consisting of Ni, Co, Mn, and Al. Specifically, it may be Li x Ni a Co b M1 c M2 1-a-b-c O 2+y (Here, M1 may include at least one of Al and Mn, and M2 may include one or more elements selected from Ba, Ca, Zr, Ti, Mg, Ta, Nb, Mo, W, P, Sr, Bi, Zn, Cr and V. The value may be 0.8 ≤ x ≤ 1.2, 0 ≤ a ≤ 1, 0 ≤ b ≤ 1, 0 ≤ c ≤ 1, 0 ≤ y ≤ 2, and preferably 0.8 ≤ x ≤ 1.2, 0 ≤ a ≤ 0.5, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.2, 0 ≤ y ≤ 2).

[0035] Hereinafter, each component of the system for analyzing metallic foreign matter in a cathode material according to the present invention will be described in detail.

[0036] (1) Pretreatment unit

[0037] A pretreatment unit is provided to produce a single-layer sample of positive electrode material powder. The pretreatment unit includes a substrate on which the positive electrode material powder is coated and a first member that removes a portion of the positive electrode material powder coated on the substrate to allow the positive electrode material particles to be distributed in a single layer.

[0038] In order to obtain particle information using an optical microscope, the particles in the observed sample must be uniformly dispersed as a single layer without any eclipse or stacking. If particle stacking or eclipse occurs in the sample, it may result in undetectable foreign matter. Therefore, in the present invention, a single-layer sample of the positive electrode material powder is manufactured by the pretreatment unit. Typically, methods such as surface modification for ligands, thin film manufacturing by Langmuir-Blodgett, or photolithography for substrates have been used to produce single-layer samples for microscopic observation. However, such methods are not suitable for application to positive electrode material powders and require special substrates or ligands, resulting in high costs and long process times. Therefore, the present invention provides a novel system and method for manufacturing a single-layer sample of positive electrode material powder, thereby reducing the cost and time required for single-layer sample manufacturing.

[0039] According to the first embodiment, in the pre-treatment section, the substrate may be a stretchable substrate, and the first member may be a pressing member.

[0040] The stretchable substrate may be a substrate having elasticity such that when the positive electrode material powder is applied to the substrate and then pressed by a pressing member, particles of the positive electrode material powder can become embedded in the surface of the substrate. For example, the substrate may be a gel pad or Teflon tape, but the present invention is not limited thereto.

[0041] The pressing member can be configured to press the positive electrode material powder coated on the stretchable substrate in one direction, thereby removing particles arranged on the upper layer of the positive electrode material powder and allowing the positive electrode material particles to be distributed as a single layer on the stretchable substrate. The pressing member can be a hard and flat object capable of applying a constant external pressure. For example, the pressing member can be a knife made of glass or ceramic material, but is not limited thereto.

[0042] The stretchable substrate may be attached to the fixed substrate via an adhesive member. The fixed substrate is configured to prevent the stretchable substrate from bending when external pressure is applied by a pressing member. For example, the fixed substrate may be a glass substrate such as a glass slide, but is not limited thereto. The adhesive member is used to bond the fixed substrate and the stretchable substrate to each other. For example, the adhesive member may be a double-sided tape, but is not limited thereto.

[0043] Figure 1 FIG. 2 shows a schematic diagram illustrating a process of manufacturing a single-layer sample in the pre-treatment section constructed as described above. Figure 1 As shown in FIG. 1 , after applying positive electrode material powder 30 to a stretchable substrate 10A, the applied positive electrode material powder is pressed in one direction using a pressing member 20A. As a result, the positive electrode material particles in the upper layer are pressed and removed by the pressing member, and only the positive electrode material particles in the lowest layer remain embedded in the surface of the stretchable substrate, thereby producing a single-layer sample.

[0044] According to a second embodiment, in the pre-processing section, the substrate may be an adhesive substrate, and the first member may be a delamination member.

[0045] The adhesive substrate may have sufficient adhesive strength to fix the particles of the positive electrode material powder thereto, but the type of the substrate is not particularly limited. For example, the adhesive substrate may be a particle trap from JOMESA or adhesive tape, but is not limited thereto.

[0046] The delamination member may have an adhesive strength lower than that of the adhesive substrate and may be capable of removing particles present in the upper layer of the positive electrode material powder applied to the adhesive substrate. For example, a DCR roller may be used, but is not limited thereto.

[0047] Here, if necessary, the pretreatment unit may further include a pressing member that presses the applied positive electrode material powder to allow the positive electrode material powder to be evenly distributed on the adhesive substrate. The pressing member may be, for example, a knife made of glass or ceramic material, but is not limited thereto.

[0048] Figure 2 FIG. 2 shows a schematic diagram illustrating a process of manufacturing a single-layer sample in the pre-treatment section constructed as described above. Figure 2 As shown, after applying positive electrode material powder 30 onto adhesive substrate 10B and uniformly spreading the positive electrode material powder using a pressing member (not shown), the particles arranged in the lowest layer of the positive electrode material powder, which are in contact with adhesive substrate 10B, adhere to adhesive substrate 10B. Then, when the applied positive electrode material powder is pressed by delamination member 20B, the positive electrode material particles in the upper layer of the positive electrode material powder adhere to delamination member 20B, which has a relatively weak adhesive strength, and are thereby removed. The positive electrode material particles in the lowest layer of the positive electrode material powder then adhere to the adhesive substrate, which has a relatively strong adhesive strength, and are then retained, thereby producing a single-layer sample.

[0049] (2) Measurement department

[0050] A measuring section is provided to obtain an optical image of a single layer sample. In the present invention, an optical microscope can be used to obtain an optical image of the single layer sample produced in the pretreatment section. When the optical microscope described in the present invention is used for foreign matter analysis, the analysis time can be significantly reduced compared to using a scanning electron microscope (SEM). Specifically, a scanning electron microscope is used to measure a 1 cm 2 An area of ​​1000 square meters would require approximately 350 hours, but optical microscopy can greatly reduce the time required, allowing the same area to be measured in about 1 hour.

[0051] Furthermore, since optical microscopes use visible light as their light source, metallic foreign matter within the cathode material can be identified from optical images obtained through the microscope by exploiting the differences in color and brightness between the cathode active material and the metallic foreign matter. Furthermore, image analysis software integrated with or linked to the optical microscope can be used to analyze information such as the size and location of metallic foreign matter.

[0052] Specifically, the optical microscope may be a digital optical microscope capable of analyzing images. Preferably, the digital optical microscope has a line-by-line scanning method, has a 16-bit grayscale per RGB pixel, and allows white balance adjustment.

[0053] Figure 10 An optical microscope according to an embodiment of the present invention is shown.

[0054] like Figure 10 As shown, the optical microscope may include a light source 100, a CCD camera 20 arranged below the light source to capture an optical image of a sample, a lens unit 30 arranged below the CCD camera to magnify the image of the sample, a mounting unit 40 arranged below the lens unit to allow the sample to be placed thereon, a driving unit 50 for moving the mounting unit and the lens unit, and a polarizing unit 60 arranged between the light source and the CCD camera to remove scattered light from the sample. Here, the sample may be a single-layer sample of the cathode material powder produced in the pretreatment unit.

[0055] Here, the light source 100 may be, for example, a high-brightness LED with an adjustable electronic shutter that can be controlled within a range of approximately 1 / 60 to approximately 1 / 20,000. It may also be preferable that the light source allows for both coaxial and ring irradiation. By adjusting the LED output, the speed of the light source's electronic shutter, and the method of irradiation, the brightness of the light source can be fine-tuned to maximize the contrast in color and brightness (brightness) between the positive electrode active material and the metallic foreign matter, thereby producing an optical image in which the metallic foreign matter is clearly identifiable.

[0056] Figure 3 The difference in optical images depending on the light source irradiation method is shown, where (A) is an optical image obtained by coaxially irradiating the sample using the light source, (B) is an optical image obtained by annularly irradiating the sample using the light source, and (C) is an optical image obtained with a 95:5 ratio of annular irradiation to coaxial irradiation with respect to the sample.

[0057] Figure 4 Spectral data depending on the light source illumination method are shown, where (A) is the brightness and color spectrum data of an optical image obtained by performing annular illumination of a sample using a light source, and (B) is the brightness and color spectrum data of an optical image obtained with a 95:5 ratio of annular illumination to coaxial illumination of the sample.

[0058] exist Figure 3 In the case of the optical image, it can be observed that the brightness and color of the optical image vary depending on the illumination method of the light source. On the other hand, when observed with the naked eye, although foreign matter seems to be most clearly identifiable for the ring illumination method, as shown in FIG. Figure 4As shown, when ring illumination and coaxial illumination are used together, the contrast in brightness and color appears more clearly. This is believed to be because the optical image obtained by the ring illumination method contains too much information, resulting in noise. Therefore, in order to improve the contrast in brightness and / or color between the positive electrode active material and the metallic foreign matter, and thereby improve the recognition of metallic foreign matter within the positive electrode material, it may be preferable to set the light source illumination method to a combination of ring illumination and coaxial illumination.

[0059] Next, a CCD camera 20 is provided to capture an image of the sample magnified by the lens section 30, and may have a resolution ranging from FHD to 4K, for example. Since the ability to identify foreign matter may be reduced when the resolution of the CCD camera is relatively too low, it may be preferable to have a resolution of FHD or higher.

[0060] Next, the lens section 30 is provided to magnify the image of the sample, and it may be preferable that the lens section 30 has a magnification of about 200 to 500 times. When the magnification of the lens section is relatively low, it may be difficult to identify foreign matter with a microscopic size, while when the magnification of the lens section is too high, the area that can be measured at one time becomes smaller, thereby increasing the measurement time.

[0061] Next, a driving unit 50 is provided to horizontally move the mounting unit 40 on which the sample is placed and vertically move the lens unit 30, and the driving unit may include a stepping motor. The driving unit is adjusted to finely move the mounting unit and the lens unit to adjust the focus while capturing an image of the sample.

[0062] Polarizing section 60 is provided to remove diffusely reflected light from materials other than the target to be detected (e.g., background and positive electrode active material), maximizing the recognition of the target (e.g., metallic foreign matter) in the optical image. Polarizing section 60 includes an upper polarizing plate 62 positioned on the light source 10 side and a lower polarizing plate 64 positioned on the CCD camera 20 side. If desired, polarizing section 60 may further include a polarizing filter 66 positioned between upper polarizing plate 62 and lower polarizing plate 64.

[0063] Here, the polarization axis angle can be adjusted to adjust the degree of diffuse reflection removal based on the type of material (e.g., positive electrode active material) contained in the sample in addition to the target. For example, the polarization axis of the upper and lower polarizers can be adjusted to an angle between 30° and 150°, depending on the type of positive electrode active material contained in the positive electrode material powder.

[0064] When analyzing samples with severe diffuse reflection, the polarizing unit can also include a polarizing filter located between the upper and lower polarizing plates to improve the identification of targets (e.g., metallic foreign matter) in the optical image. The polarizing filter can be appropriately selected based on the type of sample to be measured. For example, when analyzing positive electrode material powder containing lithium nickel cobalt manganese oxide as the positive electrode active material, a filter such as the OP-88323 from Keyence can be used, but is not limited to this.

[0065] Figure 5 is a view showing the difference in optical images depending on whether a polarizing portion is included. Figure 5 In the figure, (A) shows an optical image and spectral data captured using an optical microscope without a polarizing unit, and (B) shows an optical image and spectral data captured using an optical microscope with a polarizing unit. The light sources in (A) and (B) of this figure were illuminated in the same manner and under the same conditions.

[0066] exist Figure 5 In the optical image captured with an optical microscope including a polarizing section, it can be observed that the brightness of the active material particles and the background is darkened, thereby improving the recognition of metallic foreign matter.

[0067] After placing the single-layer sample produced in the pre-processing unit onto the mounting unit of the optical microscope described above, appropriate settings are made for the imaging mode (e.g., image setting and color adjustment conditions) and light source illumination conditions (e.g., light source brightness and illumination method). After specifying the area to be captured, the focus is adjusted by controlling the drive unit, and the sample image is captured to obtain an optical image. The obtained optical image is then transmitted to the analysis unit.

[0068] Here, the shooting mode can be appropriately adjusted according to the type of positive electrode material powder to be measured. For example, when analyzing positive electrode material powder containing lithium nickel manganese cobalt oxide as the positive electrode active material, the image settings can be configured by turning off edge intensity, gamma, and offset and setting RGB to a ratio of R: 1.78, G: 1.00, and B: 2.29. However, this is not limited to this, and if the type of positive electrode active material or the type of metallic foreign matter to be detected changes, the shooting mode conditions can also be changed.

[0069] At the same time, the light source irradiation conditions can be appropriately adjusted according to the type of positive electrode material powder to be measured. For example, when analyzing positive electrode material powder containing lithium nickel manganese cobalt oxide as the positive electrode active material, the light source irradiation conditions can be set to have a shutter speed of 35 and a ring 95: coaxial 5 ratio. However, it is not limited to this. If the type of positive electrode active material or the type of metallic foreign matter to be detected changes, the light source irradiation conditions can also be changed.

[0070] In terms of enhancing the ability to detect metallic foreign matter, it may be preferable to perform photographing at a high magnification of 300 times or more (preferably 400 times or more), and it may be desirable to use a depth-up function.

[0071] Although not required, the optical microscope may also include a laser light source 70 for analyzing the composition of metallic foreign matter. The laser light source 70 may be arranged above the mounting portion, parallel to the lens portion 30, and may be configured to move up, down, left, and right. When a laser light source is provided in the optical microscope, the composition of metallic foreign matter can be analyzed through destructive analysis using the laser light source.

[0072] As the laser light source 70 , for example, a class 1 YAG laser having a wavelength ranging from about 300 nm to about 400 nm, for example, 355 nm, may be used, but it is not limited thereto.

[0073] Furthermore, it may be preferable that the laser light source has a laser spot size of about 5 μm or more, and it is desirable that the output be variably adjustable.

[0074] Meanwhile, the laser irradiation time may be about 1 second to about 3 seconds, and it may be preferred that the laser irradiation is performed under ambient temperature and normal pressure conditions.

[0075] (3) Analysis Department

[0076] An analysis unit is provided to obtain information about foreign matter within the cathode material by analyzing the optical image obtained from the measurement unit. This analysis unit may include image analysis software integrated into or linked to the optical microscope. In this case, it is desirable that the image analysis software be capable of performing functions such as automatic area measurement, color and brightness data extraction, and filtering.

[0077] For example, the analysis unit can extract color and brightness data from the optical image transmitted by the measurement unit and use this data to determine the shape and location of the metallic foreign object. For example, if the color and brightness values extracted from the optical image match a predetermined reference color and brightness for the foreign object, the object can be identified as a metallic foreign object. By storing data such as the location, area, and size of the identified metallic foreign object, the object's shape and location information can be obtained.

[0078] The reference color and reference brightness of the foreign matter can be set by adding metallic foreign matter to the positive electrode material powder to prepare a reference sample and analyzing the reference sample according to the method of the present invention.

[0079] The analysis section may analyze the stitched image by stitching together each of the high magnification and depth synthetic optical images.

[0080] Figure 6 The results of detecting metallic foreign matter by analyzing optical images measured at 400x magnification are shown. Figure 6 (A) is a 1 cm image obtained by stitching multiple optical images. 2 (B) is a stitched image of the area, (B) is a single optical image captured at 400x magnification, and (C) is an image showing a magnified view of the area of metallic foreign matter particles identified in the optical image. Figure 6 The white part in (B) represents foreign matter. Figure 6 In the present invention, it can be observed that the analysis system of the present invention can be used to detect foreign matter having a fine size of about 10 μm or less and obtain shape information such as the size of the foreign matter.

[0081] If necessary, the positional information of the foreign metal object identified by the analysis unit can be transmitted to a measurement unit, which includes an optical microscope equipped with a laser light source. Based on the transmitted positional information, the measurement unit can illuminate the foreign metal object with a laser to obtain compositional information about the foreign metal object. Specifically, when the positional information of the foreign metal object obtained by the analysis unit is transmitted to the optical microscope, the laser light source illuminates the corresponding position based on the transmitted positional information, thereby burning the foreign metal object. The line spectrum generated during this process can be used to obtain compositional information about the foreign metal object.

[0082] Analytical methods

[0083] Next, a method for analyzing metallic foreign matter in a positive electrode material according to the present invention will be described.

[0084] The method for analyzing metal foreign matter in a positive electrode material according to the present invention includes the following processes: a first process of coating positive electrode material powder onto a substrate and then removing a portion of the coated positive electrode material powder to produce a single-layer sample; a second process of obtaining an optical image of the single-layer sample using an optical microscope; and a third process of analyzing the optical image of the single-layer sample to obtain foreign matter information within the positive electrode material.

[0085] Here, the positive electrode material powder may include various types of positive electrode material powders used in the field of secondary batteries, as described above. The positive electrode material powder may include metallic foreign matter and positive electrode active material particles. The types of metallic foreign matter and positive electrode active material are the same as described above.

[0086] The following is a detailed description of each process of the method for analyzing metallic foreign matter in a positive electrode material according to the present invention.

[0087] (1) First process: single-layer sample manufacturing process

[0088] First, a single-layer sample of the positive electrode material powder is prepared (the first process). The single-layer sample can be prepared using the following two methods.

[0089] According to the first embodiment, the first process includes: coating the positive electrode material powder to be measured on a stretchable substrate; and using a pressing member to push the positive electrode material powder coated on the stretchable substrate in one direction to remove upper layer particles of the positive electrode material powder, thereby forming a single layer.

[0090] Here, the stretchable substrate may be attached to the fixing substrate by an adhesive member, and since the stretchable substrate, the pressing member, the fixing member, and the adhesive member are the same as those described in the pre-processing part, detailed description is omitted.

[0091] Reference Figure 1 After applying the positive electrode material powder 30 to be measured onto the stretchable substrate 10A, the applied positive electrode material powder is pressed in one direction using the pressing member 20A. As a result, the positive electrode material particles in the upper layer of the positive electrode material powder are removed as they are pressed by the pressing member, and only the positive electrode material particles arranged in the lowest layer of the positive electrode material powder remain embedded on the surface of the stretchable substrate, thereby forming a single-layer sample.

[0092] Figure 7Optical images of samples fabricated using a stretchable substrate and a carbon tape are shown. (A) shows an optical image of a sample fabricated by applying positive electrode material powder to a gel pad attached to a glass slide using double-sided tape, then pressing the positive electrode material powder in one direction using a glass for applying external pressure. (B) shows an optical image of a sample fabricated by applying positive electrode material powder to a Teflon tape attached to a glass slide using double-sided tape, then pressing the positive electrode material powder in one direction using a glass for applying external pressure. (C) shows an optical image of a sample fabricated by applying positive electrode material powder to a non-stretchable carbon tape, then pressing the positive electrode material powder in one direction using a pressing member. (D) shows an optical image of a sample fabricated by spraying positive electrode material powder onto the carbon tape to prevent particle stacking.

[0093] like Figure 7 As shown, in the case of samples A and B using a stretchable substrate, the particles are densely packed and well dispersed without any interference or stacking between particles. In contrast, sample C has issues with particle stacking, which causes the lowest layer of particles to be obscured and the carbon ribbon to be damaged during pressing. For sample D, the particle density is too low, making it unsuitable for metallic foreign matter analysis, which requires large quantities of analysis.

[0094] According to a second embodiment, a first process includes: applying a positive electrode material powder to be measured onto an adhesive substrate; and removing particles from an upper layer of the positive electrode material powder applied to the adhesive substrate to form a single layer. If desired, the first process may further include pressing the positive electrode material powder using a pressing member after applying the positive electrode material powder to the adhesive substrate to allow the positive electrode material powder to be evenly distributed on the adhesive substrate.

[0095] In this case, since the adhesive base, the delamination member, and the pressing member are the same as those described in the pretreatment section, detailed description is omitted.

[0096] refer to Figure 2 After the positive electrode material powder 30 to be measured is applied to the adhesive substrate 10B and evenly spread using a pressing member (not shown), the particles in the lowest layer that are in contact with the adhesive substrate 10B adhere to the adhesive substrate 10B. Then, when the applied positive electrode material powder is pushed by the delamination member 20B, the positive electrode material particles in the upper layer of the positive electrode material powder adhere to the delamination member 20B, which has a relatively weak adhesive strength, and are removed. The positive electrode material particles in the lowest layer of the positive electrode material powder then adhere to the adhesive substrate, which has a relatively strong adhesive strength, and remain, thereby producing a single-layer sample.

[0097] Figure 8Shown are optical images of a sample (A) produced by applying positive electrode material powder to an adhesive substrate and then removing the upper layer of particles using a delaminating member, and an optical image of a sample (B) produced by applying positive electrode material powder to an adhesive substrate without using a delaminating member to remove particles. Here, a particle trap was used as the adhesive substrate, and a DCR roller was used as the delaminating member.

[0098] like Figure 8 As shown, in the case of sample A, the particles were observed to be uniformly distributed in a single layer, while in sample B, which had not undergone the particle removal process, the upper layer particles were trapped together, making it difficult to properly observe the lower layer particles and resulting in poor focusing.

[0099] (2) Second process: optical image measurement process

[0100] Next, an optical image of the single-layer sample obtained in the first process was captured using an optical microscope (second process).

[0101] Here, the second process may be performed by adjusting a light source setting and a photographing mode of the optical microscope to increase a brightness contrast between the positive electrode active material and the metallic foreign matter within the optical image.

[0102] Specifically, after placing the single-layer sample prepared in the first process on the mounting portion of an optical microscope, the optical microscope's capture mode (image setting, color adjustment, etc.) and light source settings (brightness, illumination method, etc.) are appropriately adjusted. After specifying the area to be captured and adjusting the focus by controlling the drive portion of the optical microscope, an image of the sample is captured to obtain an optical image.

[0103] Here, it may be preferable to adjust the light source setting and shooting mode to maximize the contrast in color and brightness between the background and the positive electrode active material and the metallic foreign matter in the optical image. For example, it may be preferable that the light source is set to a combination of coaxial illumination and annular illumination, and more preferably, the ratio of annular illumination to coaxial illumination can be set to 95:5. When the light source illumination conditions are set as described above, the contrast in brightness and color between the background, active material, and foreign matter in the optical image becomes clear, thereby improving the recognition of foreign matter (see Figure 3 and Figure 4 ). In addition, if necessary, the speed of the electronic shutter can be controlled to adjust the brightness of the light source. However, the light source setting conditions may vary depending on the type of cathode material to be measured.

[0104] At the same time, for example, it can be set by turning off the edge intensity, gamma and offset in the image settings and setting RGB to a ratio of R:1.78, G:1.00, B:2.29, but it is not limited to this, but can be appropriately adjusted according to the type of positive electrode material powder to be measured.

[0105] (3) The third process: optical image analysis process

[0106] Next, the optical image of the single-layer sample obtained in the second process is analyzed to obtain foreign matter information within the positive electrode material (third process).

[0107] At this time, the third process may include extracting color and brightness data from the optical image, identifying the metal foreign matter using the extracted color and brightness data, and obtaining shape information and position information of the identified metal foreign matter.

[0108] For example, identification of metallic foreign matter can be performed by comparing the color and brightness values extracted from an optical image with a predetermined reference color and brightness of the foreign matter, and identifying it as a metallic foreign matter when it meets the reference color and brightness. By storing data such as the position, area, and size of the identified metallic foreign matter, shape and position information of the metallic foreign matter can be obtained. The reference color and brightness of the foreign matter can be set by adding metallic foreign matter to positive electrode material powder to create a reference sample and analyzing the reference sample according to the present invention.

[0109] The analysis can be performed using image analysis software integrated into or linked to the optical microscope. It may be preferred that the image analysis software can perform functions such as automatic area measurement, color and brightness data extraction, and filtering.

[0110] When this method is used, it is possible to detect foreign matter having a size of approximately 10 μm or less and obtain shape information (such as the size of the foreign matter) as well as position information (see Figure 6 ).

[0111] Meanwhile, the analysis method according to the present invention may further include a process of analyzing the composition of the metallic foreign matter, if necessary.

[0112] The composition analysis process may include, for example: transmitting position information of the identified metal foreign matter to an optical microscope equipped with a laser light source; and irradiating the metal foreign matter with laser light based on the transmitted position information to obtain composition information of the metal foreign matter.

[0113] When laser light is irradiated onto a metallic foreign body, the foreign body burns due to the laser light, generating a line spectrum. By analyzing this line spectrum, the composition of the foreign body can be obtained.

[0114] At the same time, in order to prevent measurement errors caused by elements contained in the air, it may be preferable to first obtain a line spectrum by irradiating the laser in a blank state, and then analyze the composition information of the metal foreign matter by excluding the overlapping area of the line spectrum obtained from the metal foreign matter and the line spectrum obtained in the blank state.

[0115] Figure 9 The results of analyzing the composition of metallic foreign matter using laser light are shown. Specifically, it shows the line spectrum measured by irradiating laser light on two particles identified as foreign matter by optical image analysis. Figure 9 As shown, by analyzing this line spectrum, the composition of the particles can be confirmed.

Claims

1. A system for analyzing metallic foreign matter in a cathode material, the system comprising: a pretreatment unit configured to prepare a single-layer sample of positive electrode material powder; a measuring section configured to obtain an optical image of the single-layer sample using an optical microscope; as well as an analyzing unit configured to analyze the optical image of the single-layer sample to obtain information about foreign matter in the positive electrode material; The pretreatment unit includes a substrate on which the positive electrode material powder is coated, and a first member configured to remove a portion of the positive electrode material powder coated on the substrate to allow positive electrode material particles to be distributed in a single layer.

2. The system according to claim 1, wherein: The positive electrode material powder includes metallic foreign matter and positive electrode active material particles.

3. The system according to claim 2, wherein: The metallic foreign matter includes at least one material selected from the group consisting of Fe, Cr, Cu, and Zn.

4. The system according to claim 2, wherein: The positive electrode active material particles are lithium metal oxide including at least one metal element selected from the group consisting of Ni, Co, Mn, and Al.

5. The system according to claim 1, wherein: The substrate is a stretchable substrate; and The first member is a pressing member configured to press the positive electrode material powder coated on the stretchable substrate in one direction so that the positive electrode material particles are distributed as a single layer on the stretchable substrate.

6. The system according to claim 5, wherein: The stretchable substrate is a gel pad or a Teflon tape; and The pressing member is made of glass or ceramic material.

7. The system according to claim 5, wherein: The pre-treatment part further includes a fixing substrate to which the stretchable substrate is attached by an adhesive member.

8. The system according to claim 7, wherein: The fixed substrate is a glass substrate.

9. The system according to claim 1, wherein: The substrate is an adhesive substrate; and The first member is a delamination member having an adhesive force smaller than that of the adhesive substrate and removing particles present in an upper layer of the positive electrode material powder coated on the adhesive substrate to allow the positive electrode material particles to be distributed as a single layer on the adhesive substrate.

10. The system according to claim 9, wherein: The adhesive substrate is an adhesive tape, and the delamination member is a DCR roller.

11. The system according to claim 9, wherein: The pretreatment section further includes a pressing member configured to uniformly press the positive electrode material powder onto the adhesive substrate.

12. The system according to claim 1, wherein: The optical microscope comprises: Light source (10); a CCD camera (20) disposed below the light source and configured to capture an optical image of the sample; a lens portion (30), the lens portion (30) being arranged below the CCD camera and configured to magnify an image of the sample; a mounting portion (40), the mounting portion (40) being arranged below the lens portion, and the sample being placed on the mounting portion (40); a driving portion (50) configured to move the mounting portion and the lens portion; and A polarizing unit (60) is arranged between the light source and the CCD camera to eliminate diffusely reflected light from the sample.

13. The system according to claim 12, wherein: The light source is a high brightness LED with an adjustable electronic shutter in the range of 1 / 60 to 1 / 20,000.

14. The system according to claim 12, wherein: The light source allows for coaxial illumination and annular illumination.

15. The system according to claim 12, wherein: The lens portion has a magnification of 200 to 500 times.

16. The system of claim 12, wherein: The driving unit includes a stepping motor.

17. The system of claim 12, wherein: The CCD cameras have resolutions ranging from FHD to 4K.

18. The system of claim 12, wherein: The polarizing unit includes an upper polarizing plate arranged on the light source side and a lower polarizing plate arranged on the CCD camera side.

19. The system according to claim 18, wherein: The polarizing unit further includes a polarizing filter disposed between the upper polarizing plate and the lower polarizing plate.

20. The system of claim 12, wherein: The optical microscope further includes a laser light source for analyzing the composition of metallic foreign matter.

21. The system of claim 20, wherein: The laser light source is a YAG laser.

22. The system of claim 20, wherein: The laser light source has a laser spot size of 5 μm or greater.

23. The system of claim 20, wherein: The laser light source has a variably adjustable output.

24. The system of claim 1, wherein: The analyzing section extracts color and brightness data from the optical image of the single-layer sample to identify shape information and position information of the metallic foreign matter using the extracted color and brightness data.

25. The system of claim 24, wherein: The analyzing unit transmits the position information of the identified metal foreign matter to the measuring unit, and The measuring section acquires composition information of the metallic foreign matter by irradiating laser light onto the metallic foreign matter based on the transmitted position information.

26. A method for analyzing metallic foreign matter in a positive electrode material, the method comprising: a first process of coating a cathode material powder on a substrate and removing a portion of the coated cathode material powder to manufacture a single-layer sample; a second process, wherein the second process uses an optical microscope to obtain an optical image of the single-layer sample; as well as A third process is to analyze the optical image of the single-layer sample to obtain information about foreign matter in the positive electrode material.

27. The method according to claim 26, wherein The first process includes: coating the cathode material powder to be measured on a stretchable substrate; and The positive electrode material powder coated on the stretchable substrate is pressed in one direction using a pressing member to remove upper layer particles and form a single layer.

28. The method according to claim 27, wherein The stretchable substrate is attached to a fixed substrate by an adhesive member.

29. The method according to claim 26, wherein The first process includes: applying a positive electrode material powder to be measured onto an adhesive substrate; and An upper layer of particles of the positive electrode material powder coated on the adhesive substrate is removed using a delamination member to form a single layer.

30. The method of claim 26, wherein: The second process is performed by adjusting a light source setting and an imaging mode of the optical microscope so that a color and brightness contrast between the positive electrode active material and the metallic foreign matter in the optical image is increased.

31. The method according to claim 30, wherein The light source is configured as a combination of coaxial illumination and annular illumination.

32. The method according to claim 31, wherein The light source is arranged so that the ratio of annular illumination to coaxial illumination is 95:

5.

33. The method according to claim 31, wherein The third process includes extracting color and brightness data from the optical image to recognize shape information and position information of the metal foreign matter using the extracted color and brightness data.

34. The method according to claim 31, wherein The optical microscope also includes a laser light source, The third process further comprises: transmitting the position information of the identified metal foreign matter to the optical microscope equipped with the laser light source, and Laser light is irradiated onto the metal foreign matter based on the transmitted position information of the metal foreign matter to obtain composition information of the metal foreign matter.

35. An optical microscope comprising: light source; a CCD camera disposed below the light source and configured to capture an optical image of the sample; a lens portion disposed below the CCD camera and configured to magnify an image of the sample; a mounting portion arranged below the lens portion and on which the sample is placed; a driving portion configured to move the mounting portion and the lens portion; as well as A polarizing unit is arranged between the light source and the CCD camera to eliminate diffusely reflected light from the sample.

36. The optical microscope according to claim 35, wherein The light source includes an electronic shutter, which is a high-brightness LED that can be adjusted within a range of 1 / 60 to 1 / 20000.

37. The optical microscope according to claim 35, wherein The light source allows for coaxial illumination and annular illumination.

38. The optical microscope according to claim 35, wherein The lens portion has a magnification of 200 to 500 times.

39. The optical microscope according to claim 35, wherein The driving unit includes a stepping motor.

40. The optical microscope according to claim 35, wherein The CCD cameras have resolutions ranging from FHD to 4K.

41. The optical microscope according to claim 35, wherein The polarizing unit includes an upper polarizing plate arranged on the light source side and a lower polarizing plate arranged on the CCD camera side.

42. The optical microscope according to claim 41, wherein The polarizing unit further includes a polarizing filter disposed between the upper polarizing plate and the lower polarizing plate.

43. The optical microscope according to claim 35, wherein The optical microscope further includes a laser light source for analyzing the composition of metallic foreign matter.

44. The optical microscope according to claim 43, wherein The laser light source is a YAG laser.

45. The optical microscope according to claim 43, wherein The laser light source has a laser spot size of 5 μm or greater.

46. The optical microscope according to claim 43, wherein The laser light source has a variably adjustable output.

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