Method for analyzing magnetic particles contained in a secondary battery material

Abstract

The present invention relates to a method for analyzing magnetic foreign substances present in an electrode active material. Since the above-described method for analyzing magnetic foreign substances uses a base material bonded body composed of a first adhesive base material and a second adhesive base material having different light transmittances to selectively analyze only the magnetic foreign substances present inside the irradiation target sample, it is characterized by high reliability of the analysis results. Further, the above-described method for analyzing magnetic foreign substances has an advantage that the number and / or size of magnetic foreign substances can be easily analyzed with high accuracy using a shadow map and an optical image for the base material bonded body.

Description

Technical Field

[0001] The present invention relates to a secondary battery material, and more particularly, to a method for analyzing magnetic particles contained in an electrode active material.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0026223 filed on February 27, 2023 and Korean Patent Application No. 10-2023-0151738 filed on November 6, 2023, and all contents disclosed in the documents of the Korean patent applications are incorporated herein by reference.

Background Art

[0003] A lithium secondary battery is a power generation device having a laminated structure of a positive electrode / separator / negative electrode that can be charged and discharged. During charging of the lithium secondary battery, a lithium desorption reaction in which lithium contained in the positive electrode active material is oxidized and released is induced at the positive electrode inside the battery, and a lithium insertion reaction in which lithium is reduced and enters the negative electrode active material occurs at the negative electrode.

[0004] Impurities such as foreign substances (e.g., magnetic foreign substances) are inevitably generated in the above positive electrode active material and negative electrode active material due to wear of manufacturing equipment during the manufacturing process. Such impurities can reduce productivity during the manufacture of secondary batteries. In particular, when such magnetic foreign substances are present in the manufactured secondary battery, they act as factors that reduce the electrical characteristics of the secondary battery or reduce its safety through various mechanisms.

[0005] As an example, when a foreign substance having magnetism is contained in the positive electrode active material, the magnetic foreign substance may move to the negative electrode during the charge and discharge process of the secondary battery and form dendrites. Dendrites deposited from the negative electrode can penetrate the separator and cause an internal short circuit. This lowers the voltage of the secondary battery and causes serious problems with the safety of the battery such as ignition.

[0006] In order to prevent such problems in advance, there is an increasing demand to manage the content of magnetic foreign substances in the electrode slurry at the initial stage of electrode production. Therefore, conventionally, a part of the electrode active material is taken, or metal foreign substances collected using a magnet in the positive electrode active material are directly dissolved in an acidic solution, and the dissolved acidic solution is analyzed for foreign substances using an inductively coupled plasma optical emission spectrometer (ICP-OES) to detect magnetic foreign substances in the electrode active material.

[0007] However, in the above method, when the electrode active material is a positive electrode active material, due to the analysis characteristics, the wavelength position of the transition metal, which is the main component, is close to the wavelength position of the magnetic foreign substance and interference occurs, making it difficult to analyze trace amounts of magnetic foreign substances. In addition, the low-voltage failure of the secondary battery due to magnetic substances may be affected by the number and size of the magnetic substances. However, the conventional analysis method has a limitation in that it can only confirm the components and concentrations of the magnetic substances.

[0008] Therefore, there is a need for a technology that can analyze the number and size of magnetic foreign substances present in the electrode active material, particularly in the positive electrode active material, with high reliability.

Prior Art Documents

Patent Documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] Therefore, an object of the present invention is to provide a technology capable of analyzing the number and / or size of magnetic substances present in the electrode active material with high accuracy and reliability.

Means for Solving the Problems

[0011] In order to solve the above problems, In one embodiment of the present invention, Step (S1) of mixing an irradiation target sample containing an electrode active material with a magnet member provided with a first adhesive base material on its surface and collecting the irradiation target sample on the first adhesive base material; Step (S2) of cleaning the surface of the first adhesive base material on which the irradiation target sample has been collected to remove non-magnetic substances; Step (S3) of manufacturing a base material bonded body by attaching a second adhesive base material to the surface of the first adhesive base material from which non-magnetic substances have been removed; Step (S4) of separating the base material bonded body from the magnet member, and Providing a magnetic foreign matter analysis method including step (S5) of analyzing the separated base material bonded body and analyzing any one or more of the number and size of magnetic foreign matters collected on the base material bonded body.

[0012] At this time, the irradiation target sample may have a weight of 50 g to 500 g.

[0013] Further, the first adhesive base material may have a light transmittance of 30% or less in a wavelength range of 300 nm to 800 nm during UV-Vis light transmittance analysis, and the second adhesive base material may have a light transmittance of 70% or more in a wavelength range of 300 nm to 800 nm during UV-Vis light transmittance analysis.

[0014] Further, after step (S4) of separating the base material bonded body from the magnet member, it may further include a step of cleaning the surface of the base material bonded body.

[0015] Furthermore, step (S5) of analyzing the magnetic foreign matter may be performed by the following steps:

[0016] Step (S5-1) of irradiating light on the surface of the separated base material bonded body, deriving a shadow map showing the surface of the base material bonded body in pixel units from the secondary light generated, performing shadow analysis of the derived shadow map, and calculating any one or more of the number and size of magnetic foreign matters collected on the base material adherend; Step (S5-2) of separately obtaining an optical image of the surface of the base material bonded body and determining the presence or absence of magnetic foreign matters from the obtained optical image, and Step (S5-3) of verifying the calculated value obtained by shadow analysis according to the interpretation result of the optical image.

[0017] Here, the shadow map may be shown such that any one or more of color, chroma, and lightness differ in pixel units according to the sensitivity of secondary light, and may be derived by a spectroscopic apparatus using X-ray fluorescence analysis (XRF) or the like.

[0018] Also, the shadow analysis can calculate any one or more of the number and size of magnetic foreign objects by grouping pixels that satisfy the conditions already set in the shadow map and digitizing the grouped regions.

[0019] Also, the interpretation of the optical image can be performed for particles with an average size of 10 μm or more.

[0020] Also, the step (S5-3) of verifying the calculated value obtained by the shadow analysis determines the calculated value obtained by the shadow analysis at the corresponding point of the shadow map as noise when it is interpreted that there is no magnetic foreign object at a predetermined point of the optical image, and when it is interpreted that there is a magnetic foreign object at a predetermined point of the optical image, compares the shape of the magnetic foreign object interpreted in the optical image with the shape of the region grouped at the corresponding position of the shadow map, and can be performed by verifying the calculated value obtained by the shadow analysis.

[0021] On the other hand, the magnetic foreign object may contain one or more of iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu).

Advantages of the Invention

[0022] The magnetic foreign object analysis method according to the present invention uses a base material bonded body composed of a first adhesive base material and a second adhesive base material having different light transmittances, and can selectively analyze only the magnetic foreign objects present inside the irradiation target sample. Therefore, it has the characteristic of high reliability of the analysis result. Further, the magnetic foreign object analysis method has an advantage that the number and / or size of magnetic foreign objects can be easily analyzed with high accuracy using a shadow map and an optical image of the base material bonded body.

Brief Description of Drawings

[0023]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0024] The present invention can be subjected to various modifications and can have various embodiments. Therefore, specific embodiments will be described in detail in the detailed description.

[0025] However, this is not intended to limit the present invention to specific embodiments, and it can be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0026] In the present invention, terms such as "including" and "having" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and do not preclude the presence or addition possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0027] In the present invention, when a part such as a layer, film, region, plate, substrate, or member is described as being "on" another part, this includes not only the case where it is directly "above" the other part but also the case where there is another part in between. Conversely, when a part such as a layer, film, region, plate, substrate, or member is described as being "under" another part, this includes not only the case where it is directly "below" the other part but also the case where there is another part in between. Also, in the present application, being "disposed on" can include not only the upper part but also the case of being disposed in the lower part.

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

[0029] <Magnetic foreign matter analysis method>

[0030] In one embodiment of the present invention, Step (S1) of mixing an irradiation target sample containing an electrode active material and a magnet member provided with a first adhesive substrate on its surface to collect the irradiation target sample on the first adhesive substrate, Step (S2) of washing the surface of the first adhesive substrate on which the irradiation target sample has been collected to remove non-magnetic substances, Step (S3) of attaching a second adhesive substrate to the surface of the first adhesive substrate from which non-magnetic substances have been removed to produce a substrate bonded body, Step (S4) of separating the substrate bonded body from the magnet member, and A magnetic foreign matter analysis method is provided, which includes step (S5) of analyzing the separated substrate bonded body and analyzing one or more of the number and size of magnetic foreign substances collected on the substrate bonded body.

[0031] The present invention relates to a method for analyzing magnetic foreign substances contained in an electrode active material.

[0032] Generally, an electrode active material contains magnetic foreign substances inevitably mixed in the manufacturing process. Typical magnetic foreign substances include various types of metal foreign substances. For example, the magnetic foreign substances can be one or more metal foreign substances among iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu). At this time, the metal foreign substances can be contained in the form of metal particles, metal nitride particles, etc.

[0033] Among these, manganese (Mn), cobalt (Co), nickel (Ni), etc. can form a positive electrode active material in the form of a composite oxide. However, metal elements that are not combined and remain free during the manufacturing process of the positive electrode active material will remain inside the positive electrode active material and form magnetic foreign substances. In addition, magnetic foreign substances containing iron (Fe), etc. can be contained in the electrode active material due to wear of the manufacturing equipment during the manufacturing process of the electrode active material.

[0034] When manufacturing an electrode with an electrode active material containing such magnetic foreign substances, the metal foreign substances contained in the electrode can act as foreign substances that cannot participate in the electrochemical reaction during charge and discharge of the secondary battery, and unexpected defects such as voltage defects can occur.

[0035] The above magnetic foreign substances are smaller than the size of the electrode active material and are difficult to detect, and are difficult to remove through a filter or the like. Therefore, it is important to analyze the magnetic foreign substances present in the electrode active material before manufacturing the electrode of the secondary battery. In particular, in order to solve defect problems such as voltage defects, it is preferable to confirm the number and / or size of the magnetic foreign substances.

[0036] Therefore, the present invention provides a method for analyzing magnetic foreign substances contained in an electrode active material. The magnetic foreign substance analysis method mixes an irradiation target sample containing the electrode active material with a magnet member provided with a first adhesive substrate on the surface to collect the irradiation target sample on the first adhesive substrate (S1), washes the surface of the first adhesive substrate on which the irradiation target sample is collected to remove non-magnetic substances (S2), and then attaches a second adhesive substrate to the surface of the first adhesive substrate to manufacture (S3) and separate (S4) a substrate bonded body, and then analyzes (S5) the magnetic foreign substances collected inside the substrate bonded body.

[0037] Hereinafter, each step of the above magnetic foreign matter analysis method will be described in more detail.

[0038] First, the step (S1) of collecting the irradiation target sample on the above first adhesive substrate refers to the process of mixing the irradiation target sample composed of the electrode active material and the magnet member and collecting the irradiation target sample on the surface of the magnet member.

[0039] At this time, the above irradiation target sample is a sample containing the electrode active material as the main component, and may include magnetic foreign matter and / or non-magnetic foreign matter generated in the manufacturing process of the electrode active material together with the electrode active material.

[0040] The above electrode active material may include a predetermined positive electrode active material or negative electrode active material. For example, when the above electrode active material is a positive electrode active material, it may be a lithium metal composite oxide. The lithium metal composite oxide is not particularly limited as long as it is commonly applied in the industry. For example, Li x CoO2 (0.5 < x < 1.3), Li x NiO2 (0.5 < x < 1.3), Li x MnO2 (0.5 < x < 1.3), Li x Mn2O4 (0.5 < x < 1.3), Li x (Ni a Co b Mn c )O2 (0.5 < x < 1.3, 0 < a < 1, 0 < b < 1, 0 < c < 1, a + b + c = 1), Li x Ni 1-y Co y O2 (0.5 < x < 1.3, 0 < y < 1), Li x Co 1-y Mn y O2 (0.5 < x < 1.3, 0 ≤ y < 1), Li x Ni 1-y Mn y O2 (0.5 < x < 1.3, 0 ≤ y < 1), Li x (Ni a Co b Mn c)O4 (0.5 < x < 1.3, 0 < a < 2, 0 < b < 2, 0 < c < 2, a + b + c = 2), Li x Mn 2-z Ni z O4 (0.5 < x < 1.3, 0 < z < 2), Li x Mn 2-z Co z O4 (0.5 < x < 1.3, 0 < z < 2), Li x CoPO4 (0.5 < x < 1.3) and Li x FePO4 (0.5 < x < 1.3), and may contain any one or more of them. Further, the lithium metal composite oxide may be coated with a metal or metal oxide such as aluminum (Al). Further, the positive electrode active material may contain, in addition to the lithium metal composite oxide, a metal sulfide, a metal selenide, a metal halide, and the like.

[0041] Further, when the electrode active material is a negative electrode active material, it may contain a carbon material, a lithium metal, silicon, tin, or the like. When a carbon material is used as the negative electrode active material, both low-crystalline carbon and highly crystalline carbon can be used. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and representative examples of highly crystalline carbon include natural graphite, Kish graphite, pyrolytic carbon, mesophase pitch based carbon fiber, mesocarbon microbeads, mesophase pitches, and high-temperature calcined carbon such as petroleum or coal tar pitch derived cokes.

[0042] In addition, in order to obtain more accurate analysis results, the amount of the sample to be irradiated can be limited to a predetermined weight. Specifically, the sample to be irradiated can have a weight of 50 g to 500 g, and more specifically, 50 g to 400 g, 50 g to 300 g, 50 g to 200 g, 50 g to 100 g, 100 g to 500 g, 200 g to 500 g, 300 g to 500 g, 400 g to 500 g, 100 g to 300 g, 200 g to 400 g, or 100 g to 200 g.

[0043] In addition, the mixing of the sample to be irradiated and the magnet member can be performed by a method generally applied in the industry for mixing materials. For example, after the sample to be irradiated and the magnet member are respectively charged into a reactor and sealed, the reactor can be shaken or stirred by using an impeller provided inside the reactor.

[0044] In addition, the magnet member can include an electromagnet and / or a permanent magnet. The electromagnet can include both a DC electromagnet and an AC electromagnet. Further, as the permanent magnet, any magnet with ferromagnetic properties and any magnet with soft magnetic properties, such as NdFeB-based magnets, SmCo-based magnets, Ferrite magnets, Alnico magnets, FeCrCo-based magnets, Bond magnets (Nd-Fe-B-based, Sm-Fe-N-based, Sm-Co-based, Ferrite-based), etc., can be included.

[0045] In addition, the magnet member is provided with a first adhesive substrate on its surface and can collect it regardless of the presence or absence of magnetization of the substances contained in the sample to be irradiated. That is, the magnet member can collect both the electrode active material and foreign substances (for example, magnetic foreign substances and non-magnetic foreign substances) contained in the sample to be irradiated on its surface by the first adhesive substrate. For this purpose, the first adhesive substrate can be provided on the surface of the magnet member and arranged such that one surface having adhesiveness is exposed to the outside.

[0046] Further, the first adhesive substrate may be an adhesive substrate having adhesiveness on both sides, and in some cases, it may be a multi-layered substrate including a deformed layer inside the interface in contact with the magnet member for adhesion and detachment to and from the magnet member. As an example, the first adhesive substrate may be a double-sided adhesive tape, a double-sided adhesive film, a double-sided adhesive sheet, or the like.

[0047] Further, the first adhesive substrate may be an opaque substrate that is difficult to transmit light. Specifically, the first adhesive substrate may have a light transmittance of 30% or less in the wavelength range of 300 nm to 800 nm during UV-Vis light transmittance analysis.

[0048] If the light transmittance is 30% or less in the wavelength range corresponding to visible light (i.e., 300 nm to 800 nm), substances present on the first adhesive substrate can be easily confirmed with the naked eye or a microscope without any limitation on the color or chroma of the substrate. While visually confirming whether the irradiation target sample is uniformly collected on the surface, after manufacturing the substrate bonded body, in order to confirm the presence or absence and shape of magnetic foreign substances selectively collected inside the substrate bonded body of the first adhesive substrate and the second adhesive substrate, it is preferable that the light transmittance in the visible light region is low. Further, when the light transmittance in the visible light region of the first adhesive substrate is low, the first adhesive substrate can easily conceal foreign substances already attached to the surface of the magnet member before the magnet member is provided, so the accuracy and reliability of the magnetic foreign substance analysis results can be further improved.

[0049] Therefore, the first adhesive substrate may have a light transmittance of 30% or less in the wavelength range of 300 nm to 800 nm, specifically 25% or less, 20% or less, 15% or less, 10% or less, 5% or less, more than 0% and 30% or less, 5% to 30%, 5% to 20%, or 5% to 15%.

[0050] Further, the material of the first adhesive substrate is not particularly limited as long as it is not affected by magnetism. In order to satisfy the above light transmittance, it may be a resin such as cellulose, polyethylene, polypropylene, poly(ethylene-propylene), polyimide, polyacrylate, etc. in which a dye is dispersed.

[0051] Furthermore, the first adhesive substrate may have a suitable thickness within the range in which the magnetic force of the magnet member can act on magnetic foreign substances among the irradiated target samples collected on the surface. Specifically, the first adhesive substrate may be 5 μm to 200 μm, specifically 5 μm to 150 μm, 5 μm to 120 μm, 5 μm to 100 μm, 10 μm to 120 μm, 20 μm to 90 μm, 50 μm to 100 μm, or 30 μm to 80 μm. By adjusting the average thickness of the first adhesive substrate within the above range, the magnetism of the magnet member can be uniformly realized on the surface of the first adhesive substrate. Thereby, magnetic foreign substances contained in the irradiated target sample can be preferentially collected on the surface of the first adhesive substrate prior to non-magnetic substances when the irradiated target sample and the magnet member are mixed.

[0052] Next, the step (S2) of removing non-magnetic substances among the irradiated target samples collected on the surface of the first adhesive substrate refers to a process in which, among the irradiated target samples collected by the adhesive force of the first adhesive substrate through surface cleaning of the first adhesive substrate, magnetic foreign substances maintain the collected state by the magnetic force of the magnet member, and non-magnetic substances such as non-magnetic electrode active materials and non-metallic substances are desorbed from the surface. The present invention can selectively collect only the magnetic foreign substances to be analyzed on the surface of the magnet member through this process.

[0053] At this time, the non-magnetic substances include non-metallic substances that are not affected by the magnetism of the magnet member, and in some cases, may include metallic substances, diamagnetic substances, antiferromagnetic substances, etc. that are less affected by the magnetism of the magnet member.

[0054] Also, the cleaning can be performed with a predetermined cleaning liquid. Specifically, as the cleaning liquid, water and / or alcohols having 1 to 4 carbon atoms such as methanol and ethanol can be applied. Here, the water can be industrial water that does not contain impurities such as metals / metal ions affected by the magnet member, as well as fine metal solid particles, microorganisms, and organic substances. Specifically, the water can be distilled water that has undergone the distillation process one or more times, or purified water purified by ion exchange and / or reverse osmosis.

[0055] In addition, the above cleaning can be performed by controlling the injection speed of the cleaning liquid so that the electrode active material and the non-magnetic material can be detached on the first adhesive substrate, or by filling the cleaning liquid in a separate reactor and then immersing the magnet member and shaking / stirring it. In some cases, the above cleaning can selectively leave only magnetic foreign substances on the first adhesive substrate by dissolving the adhesive / adhesive layer that exhibits adhesion at the adhesive surface of the first adhesive substrate that captures the electrode active material and the non-magnetic material with the cleaning liquid.

[0056] Next, the step (S3) of manufacturing the above substrate assembly refers to the process of forming a substrate assembly in which a second adhesive substrate is attached to the surface of the first adhesive substrate on which only magnetic foreign substances remain. In this process, the magnetic foreign substances are fixed at the bonding interface between the first adhesive substrate and the second adhesive substrate, and the bonding interface does not contain magnetic foreign substances other than the magnetic foreign substances derived from the sample to be irradiated.

[0057] In the conventional magnetic foreign substance analysis using a magnet member, since magnetic foreign substances already attached to the surface of the magnet member before the analysis of the sample to be irradiated and additional magnetic foreign substances generated during the analysis process exist on the surface of the magnet member, there is a limit in that the analysis reliability for the magnetic foreign substances contained in the sample to be irradiated is not high.

[0058] However, the substrate assembly of the present invention captures magnetic foreign substances using a first adhesive substrate that can conceal magnetic foreign substances already attached to the surface of the magnet member before the analysis of the sample to be irradiated, and at the same time, uses a second adhesive substrate that allows easy light transmission to fix the magnetic foreign substances collected on the first adhesive substrate while blocking additional magnetic foreign substances generated during the analysis process from being collected on the first adhesive substrate. Thereby, the present invention can selectively capture and analyze only the magnetic foreign substances contained in the sample to be irradiated, and thus has the feature that the accuracy and reliability of the analysis results are very high.

[0059] For this purpose, the above second adhesive substrate can be a substrate having adhesiveness on one side and non-adhesiveness on the other side. Examples of such a second adhesive substrate include single-sided adhesive tapes, single-sided adhesive films, single-sided adhesive sheets, etc. The second adhesive substrate can be arranged such that the adhesive surface is adhered to the first adhesive substrate.

[0060] In addition, the second adhesive substrate may be excellent in light transmission for the analysis of magnetic foreign matters. For example, the second adhesive substrate may have a light transmittance of 70% or more in the wavelength range of 300 nm to 800 nm during UV-Vis light transmittance analysis, specifically 75% or more, 80% or more, 85% or more, 90% or more, 95% or more, 70% to 99%, 80% to 95%, 90% to 99%, 70% to 85%, or 80% to 90%.

[0061] The second adhesive substrate exhibits a high light transmittance in the wavelength range corresponding to visible light (i.e., 300 nm to 800 nm), and has the advantage that it is easy to obtain an optical image of the substrate bonded body using an optical microscope using visible light.

[0062] Next, the step of separating the substrate bonded body (S4) refers to the process of detaching the substrate bonded body in which the first adhesive substrate and the second adhesive substrate are bonded from the magnet member and preparing a specimen for analyzing the magnetic foreign matters collected inside the substrate bonded body.

[0063] At this time, foreign matters (for example, magnetic foreign matters and non-magnetic foreign matters, etc.) generated during the manufacturing process of the substrate bonded body may exist on the surface of the substrate bonded body separated from the magnet member. Among these, the foreign matters present on the surface of the second adhesive substrate may act as a factor increasing the error of the analysis result when analyzing the substrate bonded body. Therefore, in this step S4, after separating the substrate bonded body from the magnet member to improve the accuracy of the analysis result, the process of cleaning the surface of the substrate bonded body may be further performed.

[0064] The above cleaning can be performed with a predetermined cleaning liquid. Specifically, as the cleaning liquid, water and / or alcohols having 1 to 4 carbon atoms such as methanol and ethanol can be applied. Here, the water can be industrial water that does not contain impurities such as metal / metal ions affected by the magnet member, fine metal solid particles, microorganisms, and organic substances. Specifically, the water can be distilled water that has undergone the distillation process one or more times, or purified water purified by ion exchange and / or reverse osmosis, etc.

[0065] Next, the step of analyzing the magnetic foreign matter (S5) performs analysis on the base material bonded body separated from the magnet member, and refers to the process of analyzing one or more of the number and size of the magnetic foreign matter collected at the interface between the first adhesive base material and the second adhesive base material.

[0066] Here, the above analysis may include spectroscopic analysis and optical image analysis of the base material bonded body. Specifically, this step (S5) can be performed by the following steps:

[0067] Step (S5-1) of irradiating light on the surface of the separated base material bonded body to derive a shadow map showing the surface of the base material bonded body in pixel units from the secondary light generated, performing shadow analysis on the derived shadow map, and calculating one or more of the number and size of the magnetic foreign matter collected on the base material adherend; Step (S5-2) of separately acquiring an optical image of the surface of the base material bonded body and interpreting the presence or absence of magnetic foreign matter from the obtained optical image, and Step (S5-3) of verifying the calculated value obtained by shadow analysis according to the interpretation result of the optical image.

[0068] Here, the above step (S5-1) refers to the process of performing spectroscopic analysis on the base material bonded body separated from the magnet member to derive a shadow map, and analyzing the shadow of the shadow map to calculate one or more of the number and size of the magnetic foreign matter.

[0069] The above spectroscopic analysis means a method of irradiating light satisfying a predetermined wavelength on the surface of the base material bonded body, and obtaining and analyzing the secondary light generated by the magnetic foreign matter inside the base material bonded body by the irradiated light. Therefore, the above spectroscopic analysis can be performed on the surface where the second bonding base material with high light transmittance is exposed in the base material bonded body so that the irradiated light can contact the magnetic foreign matter.

[0070] Further, the spectroscopic analysis includes a process of scanning the surface of the second adhesive substrate of the substrate assembly to derive a shadow map for each element. The above scan can be performed on the entire surface of the second adhesive substrate to be analyzed, and the area of the surface of the second adhesive substrate can be adjusted within a predetermined range. Further, the above scan is performed by continuously performing a series of processes of irradiating a predetermined point on the surface of the second adhesive substrate with light satisfying a predetermined wavelength and then obtaining the generated secondary light.

[0071] Here, the means for irradiating light satisfying a predetermined wavelength, for example, the size of the light irradiation chip, can determine the area of the light irradiated on the surface of the second adhesive substrate. The area of the above light serves as a reference for imaging the secondary light scanned during the formation of the shadow map and can be expressed in pixel units. For example, when the light irradiation chip of the spectroscopic instrument has a diameter of 30 μm and the area of the surface of the second adhesive substrate is 15 mm in width × 15 mm in length, one pixel of the derived shadow map has a resolution of 30 μm, and the shadow map can be represented by 500 pixels in width × 500 pixels in length.

[0072] On the other hand, the light irradiated on the surface of the second adhesive substrate can be those commonly applied in the industry for detecting magnetic foreign substances. Specifically, the above light can be gamma rays (γ-rays), X-rays (X-rays), ultraviolet rays (UV), visible light, infrared rays (IR), electromagnetic waves, etc. Further, the spectroscopic analysis can be performed by a method capable of analyzing trace substances using the above light. For example, the spectroscopic analysis can be X-ray fluorescence analysis (XRF) that obtains fluorescent X-rays as secondary light. The above X-ray fluorescence analysis (XRF) has the advantage that even extremely trace foreign substances can be precisely analyzed by element component.

[0073] Further, the derived shadow map can be represented such that at least one of chroma, color, and lightness is different according to the sensitivity of the secondary light obtained during scanning through a predetermined software, program, etc., and this can be applied in pixel units. The above color classifies the color for chromatic and achromatic colors, the above chroma represents the darkness and lightness of the color for chromatic colors, and the above lightness represents the brightness of the color for achromatic colors.

[0074] As an example, when the shadow map is represented in achromatic colors, the brightness can be adjusted in pixel units according to the sensitivity of the obtained secondary light and then represented. In this case, when the sensitivity of the secondary light is high, the brightness of the pixel representing the location is embodied as high and can be represented in white or a color close to it. On the other hand, when the sensitivity of the secondary light is low, the brightness of the pixel representing the location is embodied as low and can be represented in black or a color close to it.

[0075] As another example, when the shadow map is represented in both chromatic and achromatic colors, the color can be adjusted in pixel units according to the sensitivity of the obtained secondary light and then represented. For example, when the sensitivity of the secondary light is high as shown in FIG. 3, the color of the pixel representing the location can be represented in yellow. On the other hand, when the sensitivity of the secondary light is low, the color of the pixel representing the location can be represented in red, which is different from yellow.

[0076] The magnetic foreign object can be identified by shadow analysis on the shadow map, and one or more of the number and size can be calculated by digitizing the identified magnetic foreign object. Specifically, the shadow analysis may mean a process of grouping pixels that satisfy the conditions already set in the shadow map mapped according to the sensitivity of the secondary light, and identifying and digitizing the grouped area as a magnetic foreign object. In this case, the already set conditions may be conditions for any one or more of saturation, color, and brightness according to the expression method of the shadow map. For example, when representing the pixels of the shadow map with a CIE LAB color difference meter, when the deviation of L*, a*, and b* between adjacent pixels satisfies a predetermined range, the pixel is recognized as the same area and grouped, and when it is larger than the above range, the pixel may not be recognized as a different area and grouped.

[0077] As an example, when each pixel of the shadow map is represented by a CIE LAB color difference meter, if the deviation of L*, a*, and / or b* between adjacent pixels is 10 or less, 5 or less, 3 or less, or 1 or less, it can be recognized as the same region and the pixels can be grouped. On the other hand, if the deviation of L*, a*, and b* between adjacent pixels exceeds 10, exceeds 5, exceeds 3, or exceeds 1, it may be recognized as a different region and the pixels may not be grouped.

[0078] As another example, when each pixel of the shadow map is represented by a CIE LAB color difference meter, if the ΔE deviation of each pixel is 10 or less, 5 or less, 3 or less, or 1 or less, it can be recognized as the same region and the pixels can be grouped. On the other hand, if the ΔE deviation between adjacent pixels exceeds 10, exceeds 5, exceeds 3, or exceeds 1, it may be recognized as a different region and the pixels may not be grouped.

[0079] In this way, when the pixels of the shadow map are grouped by shadow analysis, the grouped pixels can be specified as magnetic foreign substances, and the number and / or size of the specified regions can be quantified. In this case, the quantification can be calculated using the number of pixels in the specified region and the resolution per pixel.

[0080] In addition, the above step (S5-2) refers to the process of separately acquiring and analyzing an optical image of the surface of the spectroscopically analyzed substrate assembly (specifically, the surface of the second adhesive substrate).

[0081] The above optical image is an image obtained using an optical microscope as shown in FIG. 4, and the optical microscope can be applied without particular limitation as long as it can obtain a magnified image of the specimen surface using visible light.

[0082] The analysis of the above optical image means observing whether there is a particle shape satisfying a predetermined size in the obtained optical image and interpreting the presence or absence of magnetic foreign substances.

[0083] Conventionally, an image of a specimen has been obtained using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or the like. However, although the above electron microscope images the interaction between an electron beam and a sample using the electron beam, since the magnetic foreign matter in the present invention has a form surrounded and collected by an adhesive base material, it is difficult to have a direct interaction with the electron beam. On the other hand, an optical microscope using visible light can intuitively confirm the shape of the magnetic foreign matter collected inside the base material assembly, so the presence or absence of the magnetic foreign matter can be easily interpreted.

[0084] Also, generally, magnetic foreign matter that induces a low voltage problem or induces an internal short circuit in a secondary battery may satisfy a predetermined size. In other words, magnetic foreign matter smaller than a predetermined size may have a low possibility of causing a low voltage problem or an internal short circuit. Also, it is realistically difficult to completely remove magnetic foreign matter present in the electrode active material. Therefore, the magnetic foreign matter interpreted from the optical image may have a particle shape that satisfies a predetermined size, and a particle shape smaller than the above size may be interpreted as having no magnetic foreign matter in the base material assembly. At this time, the interpreted magnetic foreign matter may be particles with an average size of 10 μm or more. More specifically, the average size may be 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 10 μm to 200 μm, 20 μm to 200 μm, 30 μm to 200 μm, 40 μm to 200 μm, 10 μm to 150 μm, 10 μm to 100 μm, 20 μm to 100 μm, 20 μm to 80 μm, 20 μm to 60 μm.

[0085] Finally, the above step (S5-3) refers to the process of verifying the calculated value obtained by shadow analysis according to the interpretation result of the optical image.

[0086] Since the calculated value calculated by shadow analysis of the above shadow map is calculated from the result mapped according to the sensitivity of the obtained secondary X-ray, the condition for the size of the magnetic foreign matter may not be reflected. Therefore, it is preferable to verify the calculated value obtained by shadow analysis reflecting the result interpreted from the above optical image.

[0087] Therefore, in this step (S5-3), when it is determined that there is no magnetic foreign object at a predetermined point in the optical image, the calculated value obtained by shadow analysis at that point in the shadow map is determined as noise, and when it is determined that there is a magnetic foreign object at a predetermined point in the optical image, the shape of the magnetic foreign object read in the optical image is compared with the shape of the region grouped at that position in the shadow map, and the calculated value obtained by shadow analysis can be verified.

[0088] More specifically, the above verification is to confirm the position of the magnetic particles read in the optical image and the corresponding position in the shadow map, and compare the shape of the magnetic particles confirmed at each position in the optical image with the region shape of the grouped pixels, and the calculated value calculated at that position in the shadow map can be individually verified to determine whether they are the same magnetic particles.

[0089] Such verification can be performed for each of the shadow maps derived for each element, and the magnetic particles verified in each shadow map can be discriminated as magnetic particles composed of that element. For example, the above verification can be to compare a shadow map derived by performing spectroscopic analysis on iron (Fe) for the same base material joint and an optical image separately obtained to individually confirm the magnetic particles, and the magnetic particles confirmed at this time can be magnetic particles containing iron (Fe).

[0090] The present invention has the above-described configuration, so that only the magnetic foreign objects existing inside the irradiation target sample can be selectively analyzed, so that the reliability of the analysis result is high, and the number and / or size of the magnetic foreign objects can be easily analyzed with high accuracy using a shadow map and an optical image showing the surface of the base material joint containing the magnetic foreign objects in pixel units.

[0091] Hereinafter, the present invention will be described in more detail with reference to examples and experimental examples.

[0092] However, the following examples and experimental examples are illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0093] Examples 1 - 2 and Comparative Examples 1 - 2. Analysis of Magnetic Foreign Substances in Electrode Active Materials

[0094] LiNi as the positive electrode active material 0.6 Co 0.2 Mn 0.2 O2 200 g and 25 mg of iron particles having an average particle diameter (D 50 ) were charged into the reactor and then stirred to prepare the sample to be irradiated.

[0095] Thereafter, a rectangular prism - shaped permanent magnet (approx. 2 cm wide × 2 cm long × 2 cm high) was prepared as the magnet member, and the permanent magnet was charged into the reactor and mixed (S1) while stirring with the sample to be irradiated. At this time, double - sided tape was attached to the surface of the permanent magnet as the first adhesive substrate, and the presence or absence of the attachment of the double - sided tape was adjusted as shown in Table 1 below. Also, the double - sided tape had a light transmittance of about 20 - 22% in the wavelength range of 300 - 800 nm and an average thickness of about 50 - 60 μm.

[0096] Thereafter, the permanent magnet with the sample to be irradiated collected on its surface was taken out of the reactor, washed with purified water purified by reverse osmosis, and non - magnetic substances such as the positive electrode active material were desorbed (S2) from the surface of the double - sided tape.

[0097] A single - sided tape was attached to the double - sided tape from which non - magnetic substances had been removed, and a substrate bonded body in which magnetic particles were fixed to the bonding interface between the double - sided tape and the single - sided tape was manufactured (S3). At this time, the presence or absence of the attachment of the single - sided tape was adjusted as shown in Table 1 below. Also, the single - sided tape had a light transmittance of about 88 - 95% in the wavelength range of 300 - 800 nm.

[0098] The manufactured substrate bonded body was detached from the permanent magnet and separated (S4), and the surface of the separated substrate bonded body was washed with purified water purified by reverse osmosis.

[0099] The above substrate bonded body was fixed to the sample part of the XRF spectrometer so that the second adhesive substrate surface could be irradiated with X-rays. Next, after irradiating the fixed second adhesive substrate surface with X-rays, secondary X-rays generated at the irradiation point were obtained, and a series of processes of creating a shadow map in pixel units according to its sensitivity were continuously performed for spectroscopic analysis of the surface of the substrate bonded body by a mapping scanning method. At this time, the resolution and scanning speed of the above XRF spectrometer were set to 30 μm / 1 pixel and 5 ms, respectively. Also, the total area of the substrate bonded body to be scanned was set to 15 mm in width × 15 mm in length. Further, the above shadow map was created for each element of iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu) so as to have a color deviation of pixels according to the sensitivity of the obtained secondary light. Shadow analysis of the created shadow map was performed to calculate the number and size of magnetic foreign substances (S5-1). Specifically, each pixel of the created shadow map was recognized as the same region and the pixels were grouped when the ΔE deviation of each pixel was 3 or less when represented by a CIE LAB color difference meter, and the grouped regions were determined to be magnetic foreign substances. The number and respective sizes of the regions determined to be magnetic foreign substances were quantified.

[0100] Next, an optical image was obtained from the surface of the second adhesive substrate of the substrate bonded body fixed to the sample part using an optical microscope separately provided in the XRF spectrometer. At this time, the minimum resolution of the above optical microscope was 15 to 22 μm. The shape of the magnetic foreign substance was interpreted (S5-2) from the obtained optical image based on whether there was a particle shape with an average size of 20 μm.

[0101] According to the interpretation result of the optical image, the above-mentioned calculated value obtained by the shadow analysis was verified (S5-3). Specifically, in the above verification, when it was determined by interpretation that there was no magnetic foreign object at a predetermined point of the optical image, the calculated value obtained by the shadow analysis at the corresponding point of the shadow map was determined as noise. Further, when it was determined by interpretation that there was a magnetic foreign object at a predetermined point of the optical image, the calculated value obtained by the shadow analysis was verified by comparing the shape of the magnetic foreign object interpreted in the optical image with the shape of the region grouped at the corresponding position of the shadow map to confirm whether they were the same magnetic foreign object.

[0102] In order to evaluate the accuracy and reliability of the analyzed results, the error rate of each result analyzed based on the number and average size of the iron particles contained in the irradiated sample was calculated. At this time, the number of iron particles contained in the irradiated sample was calculated by respectively obtaining (1) the volume of one iron particle having an average particle diameter (D 50 ) of 25 μm and (2) the volume of 25 mg of the above iron particles, and the error rate was calculated based on the calculated number of iron particles. The results are shown in Table 1 below.

[0103]

Table 1

[0104] As shown in Table 1 above, it was confirmed that the magnetic foreign object analysis method according to the present invention has a remarkably low error rate of less than ±5% with respect to the number and size of the magnetic foreign objects contained in the irradiated sample.

[0105] From these results, it can be seen that the magnetic foreign object analysis method according to the present invention can analyze the number and size of the magnetic foreign objects contained in the electrode active material with high accuracy and reliability.

[0106] As described above, the preferred embodiments of the present invention have been described with reference thereto. However, those skilled in the art or those having ordinary knowledge in the technical field can understand that the present invention can be variously modified and changed without departing from the spirit and technical scope of the present invention described in the claims to be described later.

[0107] Therefore, the technical scope of the present invention is not limited to the content described in the summary of the invention in the specification, but is defined by the scope of claims.

Explanation of Reference Numerals

[0108] 10: Substrate bonding body 100: First adhesive substrate 200: Second adhesive substrate 300: Magnetic foreign matter derived from electrode active material A-F: Surfaces in contact with magnet members I-F: Surfaces to be analyzed

Claims

1. Mixing an irradiation target sample containing an electrode active material with a magnet member provided with a first adhesive substrate on its surface to collect the irradiation target sample on the first adhesive substrate (step S1), Washing the surface of the first adhesive substrate on which the irradiation target sample has been collected to remove non-magnetic substances (step S2), Attaching a second adhesive substrate to the surface of the first adhesive substrate from which non-magnetic substances have been removed to produce a substrate bonded body (step S3), Separating the substrate bonded body from the magnet member (step S4), and Analyzing the separated substrate bonded body and analyzing one or more of the number and size of magnetic foreign substances collected on the substrate bonded body (step S5). A method for analyzing magnetic foreign substances.

2. The magnetic foreign substance analysis method according to claim 1, wherein the first adhesive substrate has a light transmittance of 30% or less in a wavelength range of 300 nm to 800 nm during UV-Vis light transmittance analysis.

3. The magnetic foreign substance analysis method according to claim 1, wherein the second adhesive substrate has a light transmittance of 70% or more in a wavelength range of 300 nm to 800 nm during UV-Vis light transmittance analysis.

4. The step (S5) of analyzing the magnetic foreign substance is Irradiating light on the surface of the separated substrate bonded body to derive a shadow map showing the surface of the substrate bonded body in pixel units from the secondary light generated, performing shadow analysis of the derived shadow map, and calculating one or more of the number and size of magnetic foreign substances collected on the substrate adhesive body (step S5-1), Separately obtaining an optical image of the surface of the substrate bonded body and determining the presence or absence of magnetic foreign substances from the obtained optical image (step S5-2), and The magnetic foreign substance analysis method according to claim 1, which is performed by a step (S5-3) of verifying the calculated value obtained by shadow analysis according to the determination result of the optical image.

5. The magnetic foreign substance analysis method according to claim 4, wherein the shadow map is shown such that one or more of color, chroma, and lightness are different in pixel units according to the sensitivity of secondary light.

6. The magnetic foreign substance analysis method according to claim 4, wherein the shadow analysis calculates one or more of the number and size of magnetic foreign substances by grouping pixels that satisfy conditions already set in the shadow map and quantifying the grouped regions.

7. The magnetic foreign substance analysis method according to claim 4, wherein the shadow map is derived by X-ray fluorescence analysis (XRF).

8. The magnetic foreign matter analysis method according to claim 4, wherein the optical image is interpreted for particles having an average size of 10 μm or more.

9. The step (S5-3) of verifying the calculated value obtained by the shadow analysis is as follows: When it is interpreted that there is no magnetic foreign matter at a predetermined point in the optical image, the calculated value obtained by the shadow analysis at the point in the shadow map is determined as noise. When it is interpreted that there is a magnetic foreign matter at a predetermined point in the optical image, the shape of the magnetic foreign matter interpreted in the optical image is compared with the shape of the region grouped at the point in the shadow map, and the calculated value obtained by the shadow analysis is verified. The magnetic foreign matter analysis method according to any one of claims 4 to 8.

10. The magnetic foreign matter analysis method according to claim 1, further comprising a step of cleaning the surface of the base material bonded body after the step (S4) of separating the base material bonded body from the magnet member.

11. The magnetic foreign matter analysis method according to claim 1, wherein the irradiation target sample has a weight of 50 g to 500 g.

12. The magnetic foreign matter according to claim 1, contains one or more of iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu). Magnetic foreign matter analysis method.

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