Method for analyzing magnetic particles contained in secondary battery materials

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] This invention relates to a method for analyzing magnetic particles contained in secondary battery materials, particularly electrode active materials.

[0002] This application claims priority rights under Korean Patent Application No. 10-2023-0026223 dated February 27, 2023, and Korean Patent Application No. 10-2023-0151738 dated November 6, 2023, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference. [Background technology]

[0003] A lithium secondary battery is a power generation element capable of charging and discharging, consisting of a stacked structure of a positive electrode, a separator membrane, and a negative electrode. During charging, a lithium desorption reaction is induced at the positive electrode where lithium contained in the positive electrode active material is oxidized and released, and a lithium insertion reaction occurs at the negative electrode where lithium is reduced and enters the negative electrode active material.

[0004] The positive electrode active material and negative electrode active material mentioned above inevitably generate impurities such as foreign matter (e.g., magnetic foreign matter) during the manufacturing process due to wear and tear of manufacturing equipment. Such impurities can reduce productivity during the manufacturing of secondary batteries. In particular, when such magnetic foreign matter is present in the manufactured secondary battery, it acts as a factor that degrades the electrical characteristics of the secondary battery or reduces its safety through various mechanisms.

[0005] For example, if the positive electrode active material contains a magnetic foreign substance, the magnetic foreign substance may migrate to the negative electrode during the charging and discharging process of the secondary battery, forming dendrites. These dendrites deposited from the negative electrode can penetrate the separation membrane and cause an internal short circuit. This can lower the voltage of the secondary battery and cause serious safety problems such as fire.

[0006] To prevent such problems, there is a growing demand to control the content of magnetic foreign matter in the electrode slurry during the early stages of electrode production. Conventionally, magnetic foreign matter in the electrode active material has been detected by either taking a portion of the electrode active material or by directly dissolving metallic foreign matter collected in the positive electrode active material using a magnet in an acidic solution, and then analyzing the foreign matter in the dissolved acidic solution using an inductively coupled plasma spectrophotometer (ICP-OES).

[0007] However, in the above method, when the electrode active material is the positive electrode active material, the wavelength position of the transition metal, which is the main component, is close to the wavelength position of the magnetic heterogeneous material, causing interference, making it difficult to analyze trace amounts of magnetic heterogeneous material. Furthermore, low voltage failures in secondary batteries caused by magnetic material can be affected by the number and size of the magnetic material. However, conventional analytical methods have the limitation that they can only confirm the components and concentration of magnetic material.

[0008] Therefore, there is a need for a technology that can analyze the number and size of magnetic foreign matter present in electrode active materials, particularly positive electrode active materials, with high reliability. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Korean Published Patent No. 10-2019-0012516 [Overview of the project] [Problems that the invention aims to solve]

[0010] Therefore, the object of the present invention is to provide a technology that can analyze the number and / or size of magnetic materials present in an electrode active material with high accuracy and reliability. [Means for solving the problem]

[0011] To solve the above problem, In one embodiment, the present invention is described as follows: 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 attaching a second adhesive base material to the surface of the first adhesive base material from which non-magnetic substances have been removed to produce a base material bonded body 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 substances 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 the 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 the wavelength range of 300 nm to 800 nm during UV-Vis light transmittance analysis

[0014] Also, 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 substances may be performed by the following steps:

[0016] 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 of the derived shadow map, and calculating any one or more of the number and size of magnetic foreign substances collected on the base material adherent Step (S5-2) of separately obtaining an optical image of the surface of the base material bonded body and reading the presence or absence of magnetic foreign substances from the obtained optical image, and Step (S5-3): Verify the calculated values ​​obtained by shading analysis based on the interpretation results of the optical image above.

[0017] Here, the above shading map may be shown such that one or more of the color, saturation, and brightness differ on a pixel-by-pixel basis depending on the sensitivity of the secondary light, and can be derived using a spectroscopic device such as X-ray fluorescence analysis (XRF).

[0018] Furthermore, the above shading analysis can calculate one or more of the number and size of magnetic foreign objects by grouping pixels that satisfy the conditions already set in the shading map and quantifying the grouped areas.

[0019] Furthermore, the above optical image interpretation can be performed on particles with an average size of 10 μm or larger.

[0020] Furthermore, the step of verifying the calculated value obtained through the shading analysis (S5-3) may be performed by determining the calculated value obtained through the shading analysis at a predetermined location in the shading map as noise if it is determined that no magnetic foreign matter is present at that location in the optical image, and by comparing the shape of the magnetic foreign matter identified in the optical image with the shape of the area grouped at that location in the shading map, and verifying the calculated value obtained through the shading analysis, if it is determined that a magnetic foreign matter is present at that location in the optical image.

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

[0022] The magnetic foreign matter analysis method according to the present invention has the advantage of highly reliable analysis results because it can selectively analyze only magnetic foreign matter present inside the irradiated sample by using a substrate assembly composed of a first adhesive substrate and a second adhesive substrate with different light transmittances. Furthermore, the magnetic foreign matter analysis method has the advantage of being able to easily analyze the number and / or size of magnetic foreign matter with high accuracy using a shading map and optical image of the substrate assembly. [Brief explanation of the drawing]

[0023] [Figure 1] This is a process diagram illustrating the magnetic foreign matter analysis method according to the present invention. [Figure 2] This is a schematic cross-sectional view showing the structure of the substrate joint according to the present invention. [Figure 3] This is an enlarged image of a portion of the shading map of iron particles derived according to the present invention. [Figure 4] This is an enlarged image of a portion of the substrate optical image obtained according to the present invention. [Modes for carrying out the invention]

[0024] Since the present invention can be modified in various ways and may have a variety of embodiments, specific embodiments will be described in detail in the detailed description.

[0025] However, this is not intended to limit the present invention to any particular embodiment, but rather should be understood to include all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

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

[0027] Furthermore, in this invention, when a part such as a layer, film, region, plate, substrate, or component is described as being "on top" of another part, this includes not only the case where it is "directly on top" of 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 component is described as being "below" 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 this application, being "placed on top" may include being placed not only at the top but also at the bottom.

[0028] The present invention will be described in more detail below.

[0029] <Magnetic foreign material analysis method>

[0030] In one embodiment, the present invention is described as follows: Step (S1): Mix the sample to be irradiated, which contains an electrode active material, with a magnetic member having a first adhesive substrate on its surface, and collect the sample to be irradiated on the first adhesive substrate. Step (S2): Clean the surface of the first adhesive substrate on which the irradiated sample is collected to remove non-magnetic material. Step (S3) to manufacture a substrate bond by attaching a second adhesive substrate to the surface of a first adhesive substrate from which non-magnetic material has been removed. Step (S4) of separating the above-mentioned base material assembly from the magnetic member, and The present invention provides a magnetic foreign matter analysis method, which includes the step (S5) of analyzing the separated substrate assembly and analyzing one or more of the number and size of magnetic foreign matter collected in the substrate assembly.

[0031] This invention relates to a method for analyzing magnetic foreign matter contained in an electrode active material.

[0032] Generally, electrode active materials contain magnetic foreign matter that is inevitably mixed in during the manufacturing process. Typical examples of magnetic foreign matter include various types of metallic foreign matter. For example, the above magnetic foreign matter may be one or more metallic foreign matter from among iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu). In this case, the above metallic foreign matter may be included in the form of metal particles, metal nitride particles, etc.

[0033] Of these, manganese (Mn), cobalt (Co), and nickel (Ni) can constitute the positive electrode active material in the form of composite oxides. However, metal elements that are not combined during the manufacturing process of the positive electrode active material remain inside the positive electrode active material and form magnetic foreign matter. In addition, magnetic foreign matter, including iron (Fe), can be incorporated into the electrode active material due to wear and tear on the manufacturing equipment during the manufacturing process.

[0034] When electrodes are manufactured using electrode active materials containing magnetic foreign matter, the metallic foreign matter contained in the electrodes may act as foreign matter that cannot participate in the electrochemical reaction during the charging and discharging of the secondary battery, potentially causing unexpected defects such as voltage failure.

[0035] The magnetic foreign matter described above is smaller than the electrode active material and difficult to detect, and difficult to remove even through filters. Therefore, it is important to analyze the magnetic foreign matter present in the electrode active material before manufacturing the electrodes of secondary batteries, and it is especially preferable to confirm the number and / or size of the magnetic foreign matter in order to solve defects such as voltage failure.

[0036] Therefore, the present invention provides a method for analyzing magnetic foreign matter contained in an electrode active material. The above magnetic foreign matter analysis method can be carried out by mixing an irradiation target sample containing an electrode active material with a magnetic member having a first adhesive substrate on its surface to collect the irradiation target sample on the first adhesive substrate (S1), washing the surface of the first adhesive substrate on which the irradiation target sample has been collected to remove non-magnetic substances (S2), then attaching a second adhesive substrate to the surface of the first adhesive substrate to manufacture a substrate joint (S3) and separating (S4), and finally analyzing the magnetic foreign matter collected inside the substrate joint (S5).

[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 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 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 electrode active material may include a predetermined positive electrode active material or negative electrode active material. For example, when the 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, metal sulfides, metal selenides, metal halides, etc.

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

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

[0043] Furthermore, the mixing of the sample to be irradiated and the magnetic component can be carried out using methods commonly applied in this industry for material mixing. For example, the mixing can be done by placing the sample to be irradiated and the magnetic component into a reactor, sealing it, and then shaking the reactor or stirring it using an impeller or the like installed inside the reactor.

[0044] Furthermore, the above-mentioned magnetic component may include an electromagnet and / or a permanent magnet. The electromagnet may include both DC electromagnets and AC electromagnets. The permanent magnet may include both ferromagnetic and soft magnetic magnets, such as NdFeB magnets, SmCo magnets, Ferrite magnets, Alnico magnets, FeCrCo magnets, and Bond magnets (Nd-Fe-B, Sm-Fe-N, Sm-Co, Ferrite).

[0045] Furthermore, the magnetic member has a first adhesive substrate on its surface, allowing it to collect substances from the irradiated sample regardless of whether or not the substance is magnetized. In other words, the magnetic member can collect both electrode active material and foreign matter (e.g., magnetic and non-magnetic foreign matter) contained in the irradiated sample on its surface using the first adhesive substrate. For this purpose, the first adhesive substrate can be provided on the surface of the magnetic member and arranged so that one adhesive surface is exposed to the outside.

[0046] Furthermore, the first adhesive substrate may be an adhesive substrate having adhesive properties on both sides, and may, in some cases, be a multilayer substrate containing a shaped layer on the inside of the interface that comes into contact with the magnetic member for bonding and detachment to the magnetic member. As one example, the first adhesive substrate may be a double-sided adhesive tape, a double-sided adhesive film, a double-sided adhesive sheet, etc.

[0047] Furthermore, the first adhesive substrate may be an opaque substrate that does not transmit light easily. Specifically, the first adhesive substrate may have a light transmittance of 30% or less in the wavelength range of 300 nm to 800 nm when analyzed using UV-Vis light transmittance analysis.

[0048] If the light transmittance in the wavelength range corresponding to visible light (i.e., 300 nm to 800 nm) is 30% or less, substances present on the first adhesive substrate can be easily confirmed with the naked eye or a microscope, regardless of the color or saturation of the substrate. The first adhesive substrate is preferably low in the visible light region in order to visually confirm whether the irradiated sample has been uniformly collected on its surface, and to confirm the presence and shape of magnetic foreign matter selectively collected inside the substrate joint of the first and second adhesive substrates after the manufacturing of the substrate joint. Furthermore, when the first adhesive substrate has low light transmittance in the visible light region, it can easily conceal foreign matter already attached to the surface of the magnet member before the first adhesive substrate is provided to the magnet member, thereby increasing the accuracy and reliability of the magnetic foreign matter analysis results.

[0049] Therefore, the above-mentioned 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, over 0% and 30% or less, 5% to 30%, 5% to 20%, or 5% to 15%.

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

[0051] Furthermore, the first adhesive substrate may have a suitable thickness that allows the magnetic force of the magnetic member to exert on magnetic foreign matter among the irradiated sample collected on its surface. Specifically, the first adhesive substrate may be 5 μm to 200 μm thick, and more 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 to the above range, the magnetism of the magnetic member can be uniformly manifested on the surface of the first adhesive substrate. As a result, magnetic foreign matter contained in the irradiated sample can be collected on the surface of the first adhesive substrate before non-magnetic material when the irradiated sample and the magnetic member are mixed.

[0052] Next, step (S2) of removing non-magnetic substances from the irradiated sample collected on the surface of the first adhesive substrate refers to the process in which, among the irradiated sample collected by the adhesive force of the first adhesive substrate through surface cleaning of the first adhesive substrate, magnetic foreign matter is maintained in a collected state by the magnetic force of the magnetic member, while non-magnetic substances such as electrode active materials and non-metallic substances that do not have magnetism are detached from the surface. Through this process, the present invention makes it possible to selectively collect only the magnetic foreign matter to be analyzed on the surface of the magnetic member.

[0053] In this case, the non-magnetic material includes nonmetallic materials that are not affected by the magnetism of the magnetic member, and may, in some cases, include diamagnetic or antiferromagnetic materials that are less affected by the magnetism of metallic materials or the magnetic member.

[0054] Furthermore, the above cleaning may be carried out using a predetermined cleaning solution. Specifically, the cleaning solution may be water and / or an alcohol with 1 to 4 carbon atoms, such as methanol or ethanol. Here, the water may be industrial water that does not contain impurities such as metals / metal ions affected by the magnetic component, as well as trace metal solid particles, microorganisms, and organic matter. Specifically, the water may be distilled water that has undergone one or more distillation processes, or purified water that has been purified by ion exchange and / or reverse osmosis.

[0055] Furthermore, the above cleaning can be performed by controlling the spraying speed of the cleaning solution so that the electrode active material and non-magnetic material can be detached on the first adhesive substrate, or by filling a separate reactor with the cleaning solution and then immersing the magnetic member in it and shaking / stirring it. In some cases, the above cleaning can selectively leave only magnetic foreign matter on the first adhesive substrate by dissolving the adhesive / adhesive layer that embodies the adhesive force on the adhesive surface of the first adhesive substrate that collects the electrode active material and non-magnetic material with the cleaning solution.

[0056] Next, the step (S3) for manufacturing the above-mentioned substrate bond refers to the process of forming a substrate bond by attaching a second adhesive substrate to the surface of a first adhesive substrate on which only magnetic foreign matter remains. In this process, the magnetic foreign matter is fixed to the bonding interface between the first adhesive substrate and the second adhesive substrate, and the bonding interface no longer contains magnetic foreign matter other than that originating from the irradiated sample.

[0057] Conventional magnetic foreign matter analysis using magnetic members has limitations because magnetic foreign matter already adhering to the surface of the magnetic member before the analysis of the sample to be irradiated, as well as additional magnetic foreign matter generated during the analysis process, are present on the surface of the magnetic member. As a result, the analytical reliability of magnetic foreign matter contained in the sample to be irradiated is not high.

[0058] However, the substrate bonding of the present invention uses a first adhesive substrate that can conceal magnetic foreign matter already attached to the surface of the magnetic member before the analysis of the sample to be irradiated, to collect magnetic foreign matter, and at the same time uses a second adhesive substrate that allows light to pass through easily to fix the magnetic foreign matter collected on the first adhesive substrate, while blocking additional magnetic foreign matter generated during the analysis process from being collected on the first adhesive substrate. As a result, the present invention has the advantage of being able to selectively collect and analyze only the magnetic foreign matter contained in the sample to be irradiated, thus providing very high accuracy and reliability of the analysis results.

[0059] For this purpose, the second adhesive substrate may be a substrate having adhesive properties on one side and non-adhesive properties on the other side. Examples of such a second adhesive substrate include single-sided adhesive tape, single-sided adhesive film, and single-sided adhesive sheet. The second adhesive substrate may be arranged so that the adhesive side is bonded to the first adhesive substrate.

[0060] Furthermore, the second adhesive substrate may have excellent light transmission for the analysis of magnetic foreign matter. 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 when performing UV-Vis light transmittance analysis, specifically having light transmittances of 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 above-mentioned second adhesive substrate exhibits high light transmittance in the wavelength range corresponding to visible light (i.e., 300 nm to 800 nm), which has the advantage of making it easy to obtain an optical image of the substrate bond using an optical microscope that uses visible light.

[0062] Next, the step of separating the substrate assembly (S4) refers to the process of detaching the substrate assembly, in which the first adhesive substrate and the second adhesive substrate are joined, from the magnetic member, and preparing a sample for analyzing magnetic foreign matter collected inside the substrate assembly.

[0063] At this time, the substrate assembly separated from the magnetic member may have foreign matter (e.g., magnetic and non-magnetic foreign matter) on its surface that is generated during the manufacturing process of the substrate assembly. Of these, foreign matter present on the surface of the second adhesive substrate may act as a factor that increases the error in the analysis results when analyzing the substrate assembly. Therefore, in step S4, in order to improve the accuracy of the analysis results, a further step of cleaning the surface of the substrate assembly may be performed after separating the substrate assembly from the magnetic member.

[0064] The above cleaning may be carried out using a predetermined cleaning solution. Specifically, the cleaning solution may be water and / or an alcohol with 1 to 4 carbon atoms, such as methanol or ethanol. Here, the water may be industrial water that does not contain impurities such as metals / metal ions affected by the magnetic component, as well as trace metal solid particles, microorganisms, and organic matter. Specifically, the water may be distilled water that has undergone one or more distillation processes, or purified water that has been purified by ion exchange and / or reverse osmosis.

[0065] Next, the step (S5) of analyzing the magnetic foreign matter refers to the process of analyzing the substrate assembly separated from the magnetic member, and analyzing one or more of the number and size of magnetic foreign matter collected at the interface between the first adhesive substrate and the second adhesive substrate.

[0066] Here, the above analysis may include spectroscopic analysis and optical imaging analysis of the substrate assembly. Specifically, this step (S5) may be carried out by the following steps:

[0067] Step (S5-1): A shade map showing the surface of the substrate bond in pixel units is derived from secondary light generated by irradiating the surface of the separated substrate bond with light, and a shade analysis is performed on the derived shade map to calculate one or more of the number and size of magnetic foreign matter collected in the substrate bond. The steps include: separately acquiring an optical image of the surface of the above-mentioned substrate bond and determining the presence or absence of magnetic foreign matter from the obtained optical image (S5-2); and Step (S5-3): Verify the calculated values ​​obtained by shading analysis based on the interpretation results of the optical image above.

[0068] Here, step (S5-1) refers to the process of performing a spectroscopic analysis on the substrate assembly separated from the magnetic member to derive a shaded map, and then analyzing the shades of the shaded map to calculate one or more of the number and size of magnetic foreign objects.

[0069] The above-mentioned spectroscopic analysis refers to a method of analyzing secondary light generated by magnetic foreign matter inside the substrate joint by irradiating the surface of the substrate joint with light that satisfies a predetermined wavelength. Therefore, the above-mentioned spectroscopic analysis can be performed on a surface of the substrate joint where a second bonding substrate with high light transmittance is exposed, so that the irradiated light can come into contact with the magnetic foreign matter.

[0070] Furthermore, the spectroscopic analysis described above includes a process of scanning the surface of the second adhesive substrate of the substrate bond to derive a shaded map for each element. The scan may be performed over the entire surface of the second adhesive substrate to be analyzed, and the size of the surface of the second adhesive substrate may be adjusted to a predetermined range. The scan is performed by continuously irradiating a predetermined point on the surface of the second adhesive substrate with light that satisfies a predetermined wavelength, and then obtaining the resulting secondary light.

[0071] Here, the size of the means for irradiating light that satisfies a predetermined wavelength, for example, the light irradiation chip, can determine the area of ​​light irradiated onto the surface of the second adhesive substrate. The area of ​​light described above serves as a reference for imaging the secondary light scanned during the formation of the shading map and can be expressed in pixels. For example, if the light irradiation chip of the spectrometer has a diameter of 30 μm and the surface area of ​​the second adhesive substrate is 15 mm wide x 15 mm high, then one pixel of the derived shading map has a resolution of 30 μm, and the shading map can be represented by 500 pixels wide x 500 pixels high.

[0072] On the other hand, the light irradiated onto the surface of the second adhesive substrate may be the type of light commonly used in this industry to detect magnetic foreign matter. Specifically, the light may be gamma rays (γ rays), X-rays (X-rays), ultraviolet (UV), visible light, infrared (IR), electromagnetic waves, etc. Furthermore, the spectroscopic analysis may be performed using a method that can analyze trace amounts of substances using the aforementioned light. For example, the spectroscopic analysis may be X-ray fluorescence analysis (XRF) which obtains fluorescent X-rays as secondary light. X-ray fluorescence analysis (XRF) has the advantage that even extremely small amounts of foreign matter can be precisely analyzed elementally.

[0073] Furthermore, the derived shading map can be represented via predetermined software or programs such that one or more of the saturation, color, and brightness differ depending on the sensitivity of the secondary light obtained during scanning, and this can be applied on a pixel-by-pixel basis. The color distinguishes between chromatic and achromatic colors, the saturation represents the intensity of the color relative to chromatic colors, and the brightness represents the brightness of the color relative to achromatic colors.

[0074] As one example, when the above shading map is represented in achromatic colors, the brightness may be adjusted on a pixel-by-pixel basis according to the sensitivity of the secondary light obtained. In this case, if the sensitivity of the secondary light is high, the brightness of the pixels representing the location will be high, and the shading map may be represented in white or a similar color. On the other hand, if the sensitivity of the secondary light is low, the brightness of the pixels representing the location will be low, and the shading map may be represented in black or a similar color.

[0075] As another example, when the above shading map is represented using both chromatic and achromatic colors, the color may be adjusted on a pixel-by-pixel basis according to the sensitivity of the secondary light obtained. For example, as shown in Figure 3, if the sensitivity of the secondary light is high, the color of the pixel representing that location may be yellow. On the other hand, if the sensitivity of the secondary light is low, the color of the pixel representing that location may be red, which is different from yellow.

[0076] The above shading map allows for the identification of magnetic foreign matter through shading analysis, and the quantification of the identified magnetic foreign matter allows for the calculation of one or more of its number and size. Specifically, the above shading analysis may mean the process of grouping pixels that satisfy already set conditions in a shading map mapped according to the sensitivity of secondary light, and identifying and quantifying the grouped areas as magnetic foreign matter. In this case, the above already set conditions may be conditions for one or more of saturation, color, and brightness, depending on the representation method of the shading map. For example, when representing the pixels of the above shading map with a CIE LAB colorimeter, if the deviations of L*, a*, and b* between adjacent pixels meet a predetermined range, the pixels may be recognized as belonging to the same area and grouped; if they are greater than the above range, the pixels may be recognized as belonging to different areas and not grouped.

[0077] As one example, when each pixel of the above shading map is represented by a CIE LAB colorimeter, if the deviations of L*, a*, and / or b* between adjacent pixels are 10 or less, 5 or less, 3 or less, or 1 or less, the pixels may be recognized as belonging to the same region and grouped together. On the other hand, if the deviations of L*, a*, and b* between adjacent pixels are greater than 10, greater than 5, greater than 3, or greater than 1, the pixels may be recognized as belonging to different regions and not grouped together.

[0078] As another example, when each pixel of a shading map is represented by a CIE LAB colorimeter, if the ΔE deviation of each pixel is 10 or less, 5 or less, 3 or less, or 1 or less, the pixels may be recognized as belonging to the same region and grouped together. On the other hand, if the ΔE deviation between adjacent pixels is greater than 10, greater than 5, greater than 3, or greater than 1, the pixels may be recognized as belonging to different regions and not grouped together.

[0079] In this way, by grouping pixels in a shaded map using shaded analysis, the grouped pixels can be identified as magnetic foreign objects, and the number and / or size of the identified regions can be quantified. In this case, the above quantification can be calculated using the number of pixels in the identified region and the resolution per pixel.

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

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

[0082] The analysis of the optical image described above involves observing whether particle shapes meeting a predetermined size exist in the obtained optical image, and determining whether or not magnetic foreign matter is present.

[0083] Conventionally, images of specimens have been obtained using scanning electron microscopes (SEMs) or transmission electron microscopes (TEMs). However, these electron microscopes use an electron beam to visualize the interaction between the electron beam and the sample, but since the magnetic foreign matter in this invention is collected surrounded by the adhesive substrate, direct interaction with the electron beam is difficult. On the other hand, optical microscopes using visible light allow for intuitive confirmation of the shape of magnetic foreign matter collected inside the substrate joint, making it easy to determine whether or not magnetic foreign matter is present.

[0084] Furthermore, magnetic foreign matter that generally induces low-voltage problems or internal short circuits in secondary batteries may meet a predetermined size. In other words, magnetic foreign matter smaller than the predetermined size may be less likely to cause low-voltage problems or internal short circuits. Also, it is practically difficult to completely remove magnetic foreign matter present in the electrode active material. Therefore, magnetic foreign matter readable in optical images may have a particle shape that meets a predetermined size, and particle shapes smaller than the above size can be interpreted as the absence of magnetic foreign matter within the substrate junction. In this case, the magnetic foreign matter that can be identified may be particles with an average size of 10 μm or more, and more specifically, particles with an average size of 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, and 20 μm to 60 μm.

[0085] Finally, step (S5-3) refers to the process of verifying the calculated values ​​obtained through shading analysis in accordance with the interpretation results of the optical image.

[0086] The calculated values ​​obtained by shadow analysis of the shadow map described above are derived from the results mapped according to the sensitivity of the obtained secondary X-rays, and therefore may not reflect the conditions related to the size of the magnetic foreign object. For this reason, it is preferable to verify the calculated values ​​obtained by shadow analysis in accordance with the results interpreted from the optical image described above.

[0087] Therefore, in this step (S5-3), if it is determined that no magnetic foreign matter is present at a predetermined location in the optical image, the calculated value obtained by shading analysis at that location in the shading map is judged to be noise. If it is determined that a magnetic foreign matter is present at a predetermined location in the optical image, the calculated value obtained by shading analysis can be verified by comparing the shape of the magnetic foreign matter identified in the optical image with the shape of the region grouped at that location in the shading map.

[0088] More specifically, the above verification can confirm the location where magnetic particles are identified in the optical image and the corresponding location in the shading map, compare the shape of the magnetic particles identified at each location in the optical image with the region shape of the grouped pixels, and individually verify whether the calculated value obtained at that location in the shading map is for the same magnetic particle.

[0089] Such verification can be performed on each of the shaded maps derived for each element, and the magnetic particles verified in each shaded map can be identified as magnetic particles composed of that element. For example, the above verification can be performed on the same substrate assembly, comparing the shaded map derived from spectroscopic analysis of iron (Fe) with separately acquired optical images to individually identify magnetic particles, and the magnetic particles identified in this case may be magnetic particles containing iron (Fe).

[0090] The present invention, having the above-described configuration, has the advantage of being able to selectively analyze only magnetic foreign matter present inside the irradiated sample, thus providing high reliability in the analysis results, and allowing for easy and highly accurate analysis of the number and / or size of magnetic foreign matter using a shaded map and optical image that show the surface of the substrate assembly containing magnetic foreign matter at the pixel level.

[0091] The present invention will be described in more detail below 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 matter in electrode active materials.

[0094] LiNi 0.6 Co 0.2 Mn 0.2 O2200g and an average particle size of approximately 25μm (D 50 25 mg of iron particles containing ) were added to the reactor and stirred to prepare the sample to be irradiated.

[0095] Subsequently, a rectangular prism-shaped permanent magnet (approximately 2 cm wide x 2 cm long x 2 cm high) was prepared as the magnetic component. This permanent magnet was placed in the reactor and mixed with the sample to be irradiated while stirring (S1). 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 double-sided tape was adjusted as shown in Table 1 below. The double-sided tape had a light transmittance of approximately 20-22% in the wavelength range of 300-800 nm and an average thickness of approximately 50-60 μm.

[0096] Subsequently, the permanent magnet, on which the irradiated sample had been collected, was removed from the reactor and washed with purified water purified by reverse osmosis to detach non-magnetic materials such as the positive electrode active material from the surface of the double-sided tape (S2).

[0097] A substrate bond was manufactured (S3) by attaching a single-sided tape to a double-sided tape from which non-magnetic material had been removed, and fixing magnetic particles at the bonding interface between the double-sided tape and the single-sided tape. At this time, the presence or absence of attachment of the single-sided tape was adjusted as shown in Table 1 below. Furthermore, the light transmittance of the single-sided tape in the wavelength range of 300 to 800 nm was approximately 88 to 95%.

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

[0099] The above-mentioned substrate assembly was fixed to the sample section of an XRF spectrometer so that X-rays could be irradiated onto the surface of the second adhesive substrate. Next, after irradiating the fixed surface of the second adhesive substrate with X-rays, secondary X-rays generated at the irradiation point were obtained, and a series of processes were carried out in a mapping scanning manner to create a shaded map on a pixel-by-pixel basis according to the sensitivity of the secondary X-rays. At this time, the resolution and scan speed of the XRF spectrometer were set to 30 μm / 1 pixel and 5 ms, respectively. The total area of ​​the substrate assembly to be scanned was set to 15 mm wide x 15 mm high. Furthermore, the shaded maps were created for each element, iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu), so that the pixel color deviation was according to the sensitivity of the obtained secondary light. Shading analysis was performed on the created shaded maps to calculate the number and size of magnetic foreign matter (S5-1). Specifically, each pixel in the created shading map was recognized as belonging to the same region if its ΔE deviation was 3 or less when represented by a CIE LAB colorimeter. These pixels were then grouped together, and the grouped regions were identified as magnetic foreign objects. The number of regions identified as magnetic foreign objects and their respective sizes were quantified.

[0100] Next, an optical microscope separately attached to the XRF spectrometer was used to obtain an optical image from the surface of the second adhesive substrate of the substrate assembly fixed to the sample. At this time, the minimum resolution of the optical microscope was 15-22 μm. The shape of the magnetic foreign matter was determined from the optical image obtained based on whether or not particle shapes with an average size of 20 μm were present (S5-2).

[0101] The calculated values ​​obtained through the shading analysis described above were verified according to the interpretation of the optical image (S5-3). Specifically, in the above verification, if it was determined that no magnetic foreign matter was present at a predetermined location in the optical image, the calculated value obtained through the shading analysis at that location in the shading map was judged to be noise. Furthermore, if it was determined that a magnetic foreign matter was present at a predetermined location in the optical image, the calculated value obtained through the shading analysis was verified by comparing the shape of the magnetic foreign matter identified in the optical image with the shape of the area grouped at that location in the shading map to confirm whether they were the same magnetic foreign matter.

[0102] To evaluate the accuracy and reliability of the analyzed results, the error rate for each result was calculated based on the number and average size of iron particles contained in the irradiated sample. In this case, the number of iron particles contained in the irradiated sample was (1) the average particle size (D) of 25 μm. 50 The volume of one iron particle having (2) and the volume of 25 mg of the above iron particles were determined and calculated, 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, the magnetic foreign matter analysis method according to the present invention was confirmed to have an extremely low error rate of less than ±5% for the number and size of magnetic foreign matter contained in the irradiated sample.

[0105] These results demonstrate that the magnetic foreign matter analysis method according to the present invention can analyze the number and size of magnetic foreign matter contained in the electrode active material with high accuracy and reliability.

[0106] While preferred embodiments of the present invention have been described above with reference to those skilled in the art or those with ordinary knowledge in the art, it will be understood that the present invention can be modified and altered in various ways without departing from the spirit and technical scope of the invention as described in the claims below.

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

[0108] 10: Base material assembly 100: First adhesive base material 200: Second adhesive base material 300: Magnetic foreign matter derived from electrode active material AF: Surface in contact with the magnetic component IF: Analysis target area

Claims

1. Step (S1): Mix a sample containing an electrode active material with a magnetic member having a first adhesive substrate on its surface, and collect the sample on the first adhesive substrate. Step (S2): Wash the surface of the first adhesive substrate from which the sample was collected to remove non-magnetic material. Step (S3) to manufacture a substrate bond by attaching a second adhesive substrate to the surface of a first adhesive substrate from which non-magnetic material has been removed. The steps of separating the base material assembly from the magnetic member (S4), and The process includes the step (S5) of analyzing the separated substrate assembly and analyzing one or more of the number and size of magnetic foreign matter collected in the substrate assembly, The first adhesive substrate is made of a material that has a light transmittance of 30% or less in the wavelength range of 300 nm to 800 nm and is not affected by magnetism. The second adhesive substrate has a light transmittance of 70% or more in the wavelength range of 300 nm to 800 nm. The step of analyzing the magnetic foreign matter (S5) is as follows: A method for analyzing magnetic foreign matter, comprising the steps (S5-1) of: irradiating the surface of a separated substrate assembly with light to generate secondary light, deriving a shade map showing the surface of the substrate assembly in pixel units from the generated secondary light; performing a shade analysis on the derived shade map; and calculating one or more of the number and size of magnetic foreign matter collected on the substrate assembly.

2. The step of analyzing the magnetic foreign matter (S5) is as follows: The steps include: separately acquiring an optical image of the surface of the substrate bonded body and determining the presence or absence of magnetic foreign matter from the obtained optical image (S5-2); The magnetic foreign matter analysis method according to claim 1, further comprising the step (S5-3) of verifying the calculated value obtained by shading analysis according to the result of interpreting the optical image.

3. The magnetic foreign matter analysis method according to claim 2, wherein the shading map is shown such that one or more of the color, saturation, and brightness differ on a pixel-by-pixel basis according to the sensitivity of the secondary light.

4. The magnetic foreign matter analysis method according to claim 2, wherein the shadow analysis involves grouping pixels that satisfy conditions already set in the shadow map, and calculating one or more of the number and size of magnetic foreign matter by quantifying the grouped areas.

5. The method for analyzing magnetic foreign matter according to claim 2, wherein the shadow map is derived by X-ray fluorescence analysis (XRF).

6. The method for analyzing magnetic foreign matter according to claim 2, wherein the interpretation of the optical image is performed on particles with an average size of 10 μm or more.

7. The step of verifying the calculated values ​​obtained through the shadow analysis (S5-3) is as follows: If it is determined that no magnetic foreign matter is present at a given point in the optical image, the calculated value obtained from the shading analysis at that point in the shading map is judged to be noise. A method for analyzing magnetic foreign matter according to any one of claims 2 to 6, wherein, when a magnetic foreign matter is detected at a predetermined location in the optical image, the shape of the magnetic foreign matter detected in the optical image is compared with the shape of the region grouped at that location in the shading map, and the calculated value obtained by shading analysis is verified.

8. The magnetic foreign matter analysis method according to claim 1, further comprising the step of cleaning the surface of the substrate assembly after the step of separating the substrate assembly from the magnetic member (S4).

9. The method for analyzing magnetic foreign matter according to claim 1, wherein the sample has a weight of 50 g to 500 g.

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

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