Method for analyzing magnetic particles included in secondary battery material

Abstract

The present technology relates to a method for analyzing magnetic foreign matter present in an electrode active material. The magnetic foreign matter analysis method according to the present invention is characterized in that only a magnetic foreign matter present inside a sample to be investigated can be selectively analyzed by using a substrate assembly comprising a first adhesive substrate and a second adhesive substrate having different light transmittances, and thus the analysis result is highly reliable. Furthermore, the method for analyzing the magnetic foreign matter is advantageous in that the number and / or size of the magnetic foreign matter can be easily analyzed with high accuracy by using the shadow map and the optical image of the substrate assembly.

Description

Technical Field

[0001] The present invention relates to a method for analyzing magnetic particles included in a secondary battery material, particularly 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 06, 2023, and the entire contents of the Korean Patent Application are incorporated herein by reference. Background Art

[0003] A lithium secondary battery is a power generation device that is capable of charging and discharging and is composed of a stacked structure of a positive electrode / separator / negative electrode. When a lithium secondary battery is charged, a lithium dissociation reaction is caused at the positive electrode inside the battery, in which lithium contained in the positive electrode active material is oxidized and released, and a lithium insertion reaction occurs at the negative electrode, in which lithium is reduced and enters the negative electrode active material.

[0004] During the manufacture of positive electrode active materials and negative electrode active materials, impurities such as foreign matter (e.g., magnetic foreign matter) inevitably occur due to the wear of manufacturing equipment. Such impurities may reduce the productivity in the manufacture of secondary batteries. In particular, when such magnetic foreign matter exists in the manufactured secondary batteries, they may reduce the electrical characteristics of the secondary batteries or reduce the safety through various mechanisms.

[0005] As an example, if magnetic foreign matter is included in the positive electrode active material, the magnetic foreign matter may move to the negative electrode during the charging and discharging process of the secondary battery and form dendrites. Dendrites precipitated from the negative electrode may penetrate the separator and cause an internal short circuit. This reduces the voltage of the secondary battery and causes serious problems with battery safety, such as ignition.

[0006] In order to prevent such problems in advance, there is an increasing demand to control the content of magnetic foreign matter in electrode slurry at an early stage of electrode production. Therefore, conventionally, magnetic foreign matter in electrode active materials is detected by removing a portion of the electrode active material or by directly dissolving the captured metallic foreign matter in an acidic solution using a magnet in the positive electrode active material and analyzing the dissolved acidic solution by inductively coupled plasma optical emission spectroscopy (ICP-OES).

[0007] However, in the above method, when the electrode active material is a positive electrode active material, it is difficult to analyze a small amount of magnetic foreign matter because the wavelength position of the transition metal as the main component of the analysis is close to the wavelength position of the magnetic foreign matter, causing interference. In addition, the low voltage failure of the secondary battery caused by the magnetic material may be affected by the amount or size of the magnetic material. However, conventional analysis methods are limited because they can only determine the composition and concentration of the magnetic material.

[0008] Therefore, there is a need for a technology capable of analyzing the amount or size of magnetic foreign matter present in an electrode active material (particularly a positive electrode active material) with improved reliability.

[0009] [Related technical literature]

[0010] [Patent Document]

[0011] Korean Patent Publication No.10-2019-0012516 Summary of the invention

[0012] [Technical issues]

[0013] It is therefore an object of the present invention to provide a technique for analyzing the amount and / or size of magnetic materials present in an electrode active material with high accuracy and reliability.

[0014] [Technical solution]

[0015] In order to solve the above problems,

[0016] In one embodiment, the present invention provides

[0017] The sample under investigation including the electrode active material is captured on the first adhesive substrate by mixing the sample under investigation including the electrode active material with a magnetic member provided with the first adhesive substrate on the surface thereof (S1),

[0018] The non-magnetic material S2 is removed by cleaning the surface of the first bonding substrate on which the sample under investigation is captured,

[0019] The substrate assembly S3 is manufactured by attaching the second adhesive substrate to the surface of the first adhesive substrate from which the non-magnetic material has been removed,

[0020] separating the substrate assembly from the magnetic member S4; and

[0021] The separated substrate assembly is analyzed to analyze at least one of the quantity and size of magnetic foreign matter entrained in the substrate assembly S5.

[0022] In this case, the subject sample may have a weight of 50 grams to 500 grams.

[0023] Furthermore, the first bonding substrate has a transmittance of 30% or less in the range from 300 nm to 800 nm when UV-Vis transmittance is analyzed, and the second bonding substrate has a transmittance of 70% or more in the range from 300 nm to 800 nm when UV-Vis transmittance is analyzed.

[0024] In addition, after separating the substrate component from the magnetic member S4, the surface of the substrate component may be cleaned.

[0025] In addition, the analysis of magnetic foreign matter S5 can be performed by the following steps:

[0026] Calculating at least one of the number and size of magnetic foreign matter captured in the substrate component by irradiating light onto the surface of the separated substrate component, deriving a shadow map representing the surface of the substrate component in pixel units from the generated secondary light, and performing shadow analysis of the derived shadow map (S5-1),

[0027] reading the presence of magnetic foreign matter in the optical image of the surface of the substrate assembly obtained alone S5-2; and

[0028] The calculated value S5-3 from the shadow analysis is verified based on the reading result of the optical image. .

[0029] Here, the shadow map may be a pixel unit representation of one or more of color, saturation and brightness depending on the sensitivity of the secondary light. Additionally, the shadow map may be derived by a spectroscopic device using X-ray fluorescence (XRF) or the like.

[0030] Furthermore, the shadow analysis may calculate at least one of the number and size of the magnetic foreign matter by grouping pixels satisfying a preset condition in the shadow map and quantifying the grouped areas.

[0031] Furthermore, optical image reading can be performed on particles having an average size of 10 μm or more.

[0032] In addition, verification of the calculated value S5-3 from the shadow analysis can be performed as follows: if it is read that the magnetic foreign matter does not exist at a predetermined point in the optical image, the calculated value at the corresponding point of the shadow map from the shadow analysis is judged to be a noise point; and if it is read that the magnetic foreign matter exists at a predetermined point in the optical image, the calculated value is verified by comparing the shape of the magnetic foreign matter read in the optical image with the shape of the grouped area at the corresponding position of the shadow map.

[0033] Meanwhile, the magnetic foreign matter may include one or more of iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu).

[0034] [Beneficial Effects]

[0035] According to the magnetic foreign matter analysis method of the present invention, it is characterized in that by using a substrate assembly including a first adhesive substrate and a second adhesive substrate having different light transmittances, only magnetic foreign matter present inside the sample under investigation can be selectively analyzed, and thus the analysis result is highly reliable. In addition, the method for analyzing magnetic foreign matter has the advantage that by using a shadowgraph and an optical image of the substrate assembly, the number and / or size of the magnetic foreign matter can be easily analyzed with high accuracy. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a process diagram illustrating a method for analyzing magnetic foreign matter according to the present invention.

[0037] Figure 2 is a cross-sectional view schematically illustrating the structure of a substrate assembly according to the present invention.

[0038] Figure 3 is an enlarged image of a portion of a shadowgram of an iron particle obtained according to the present invention.

[0039] Figure 4 is a magnified image of a portion of an optical image of a substrate obtained according to the present invention. DETAILED DESCRIPTION

[0040] The present invention can have various modifications and various embodiments, and therefore specific embodiments thereof will be described in detail below.

[0041] However, it should be understood that the present invention is not limited to the specific embodiments and includes all modifications, equivalents or substitutes within the spirit and technical scope of the present invention.

[0042] The terms "include", "comprising" and "having" as used herein indicate the presence of features, numbers, steps, actions, components or members, or a combination thereof, described in the specification, and it should be understood that the possibility of the presence or addition of one or more other features, numbers, steps, actions, components, members, or a combination thereof is not excluded in advance.

[0043] In addition, in the present invention, when a part of a layer, film, region, plate, etc. is disposed "on" another part, this includes not only a case where one part is disposed "directly" on another part, but also a case where another part is inserted therebetween. Conversely, when a part of a layer, film, region, plate, etc. is disposed "below" another part, this includes not only a case where one part is disposed "directly below" another part, but also a case where another part is inserted therebetween. In addition, in the present application, "on" may include not only a case where it is disposed on the upper part, but also a case where it is disposed on the lower part.

[0044] Hereinafter, the present invention is described in more detail.

[0045] A method for analyzing magnetic foreign matter

[0046] In one embodiment, the present invention provides

[0047] The sample under investigation S1 is captured on the first adhesive substrate by mixing the sample under investigation including the electrode active material with the magnetic member provided with the first adhesive substrate on the surface,

[0048] The non-magnetic material S2 is removed by cleaning the surface of the first bonding substrate on which the sample under investigation is captured,

[0049] The substrate assembly S3 is manufactured by attaching the second adhesive substrate to the surface of the first adhesive substrate from which the non-magnetic material has been removed,

[0050] separating the substrate assembly from the magnetic member S4; and

[0051] An analysis is performed on the separated substrate assembly to analyze at least one of the amount and size of magnetic foreign matter entrained in the substrate assembly S5.

[0052] The present invention relates to a method for analyzing magnetic foreign matter included in an electrode active material.

[0053] Generally, the electrode active material includes magnetic foreign matter that is inevitably mixed during the manufacturing process. As representative magnetic foreign matter, there are various types of metal foreign matter. For example, the magnetic foreign matter may be one or more metal foreign matter selected from iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti), and copper (Cu). In this case, the metal foreign matter may be included in the form of metal particles, metal nitride particles, etc.

[0054] Among them, manganese (Mn), cobalt (Co), nickel (Ni), etc. can constitute the positive electrode active material in the form of a composite oxide. However, during the preparation process of the positive electrode active material, the metal elements that are not composited and remain inside the positive electrode active material form magnetic foreign matter. In addition, due to the wear of manufacturing equipment during the manufacturing process of the electrode active material, magnetic foreign matter including iron (Fe) and the like may be included in the electrode active material.

[0055] When an electrode is manufactured from an electrode active material containing such magnetic foreign matter, the metallic foreign matter included in the electrode may act as a foreign matter that cannot participate in electrochemical reactions during charge and discharge of a secondary battery, thereby causing unexpected malfunctions such as voltage failure and the like.

[0056] Since magnetic foreign matter is smaller than the size of the electrode active material, it is difficult to detect them, and it is difficult to remove them by a filter, etc. Therefore, it is important to analyze the magnetic foreign matter present in the electrode active material before manufacturing the electrode of the secondary battery, and it is particularly desirable to check the amount and / or size of the magnetic foreign matter in order to solve defect problems such as voltage defects.

[0057] Therefore, the present invention provides a method for analyzing magnetic foreign matter included in an electrode active material. The method for analyzing magnetic foreign matter can be performed by mixing a survey object sample including an electrode active material with a magnetic member having a first adhesive substrate on the surface, capturing the survey object sample on the first adhesive substrate (S1), cleaning the surface of the first adhesive substrate on which the survey object sample is captured to remove non-magnetic substances (S2), attaching a second adhesive substrate to the surface of the first adhesive substrate to make a substrate assembly (S3) and separating it (S4), and then analyzing the magnetic foreign matter captured inside the substrate assembly (S5).

[0058] Hereinafter, each step of the above magnetic foreign matter analysis method will be described in more detail.

[0059] First, capturing the survey object sample on the first adhesive substrate S1 refers to a process of mixing the survey object sample including an electrode active material with a magnetic member to capture the survey object sample on the surface of the magnetic member.

[0060] At this time, the survey target sample is a sample including an electrode active material as a main component, and may include magnetic foreign matter and / or non-magnetic foreign matter generated together with the electrode active material in a manufacturing process of the electrode active material.

[0061] The electrode active material may include a predetermined positive electrode active material or a predetermined negative electrode active material. For example, if the electrode active material is a positive electrode active material, the electrode active material may be a lithium metal composite oxide. The lithium metal composite oxide is not particularly limited as long as it is conventionally used in the art, but may be, 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 yO2 (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). In addition, the lithium metal composite oxide may be coated with a metal or a metal oxide, such as aluminum (Al). In addition, in addition to the lithium metal composite oxide, the positive electrode active material may further include metal sulfides, metal selenides, metal halides, etc.

[0062] In addition, when the electrode active material is a negative electrode active material, the electrode active material may include a carbon material, lithium metal, silicon, tin, etc. When a carbon material is used as the negative electrode active material, low-crystalline carbon and high-crystalline carbon, etc. may be used. Examples of low-crystalline carbon include soft carbon and hard carbon, while examples of high-crystalline carbon include natural graphite, aggregated graphite and pyrolytic carbon, mesophase pitch-based carbon fiber, mesophase microspheres, mesophase pitch, and high-temperature calcined carbon, such as coke derived from petroleum or coal tar pitch, etc.

[0063] In addition, the subject sample may be limited to a predetermined weight in order to obtain more accurate analysis results. Specifically, the subject sample may have a weight of 50 g to 500 g, and more specifically, it may have a weight of 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.

[0064] In addition, the mixing of the sample under investigation and the magnetic member can be performed in a manner commonly practiced in the art for mixing materials. For example, it can be performed by introducing the sample under investigation and the magnetic member into a reactor, respectively, sealing the reactor, and then shaking the reactor or stirring the reactor using an impeller or the like disposed in the reactor.

[0065] In addition, the magnetic member may include an electromagnet and / or a permanent magnet. The electromagnet may include both a DC electromagnet and an AC electromagnet. In addition, the permanent magnet may include a ferromagnetic magnet and a soft magnetic magnet, including NdFeB-based magnets, SmCo-based magnets, ferrite magnets, Alnico magnets, FeCrCo-based magnets, Bond magnets (Nd-Fe-B, Sm-Fe-N, Sm-Co, ferrite), etc.

[0066] In addition, the magnetic member may be provided with a first adhesive substrate on its surface to capture substances included in the sample under investigation, regardless of whether they are magnetized. In other words, the magnetic member may capture both the electrode active material and foreign matter (e.g., magnetic foreign matter and non-magnetic foreign matter) included in the sample under investigation on its surface through the first adhesive substrate. To this end, the first adhesive substrate may be arranged on the surface of the magnetic member, but may be arranged so that the side having the adhesive property is exposed to the outside.

[0067] In addition, the first adhesive substrate may be an adhesive substrate having adhesive properties on both sides, and in some cases, may be a multilayer substrate including a release layer on the inner side of the interface with the magnetic member for bonding and detaching from the magnetic member. As an example, the first adhesive substrate may be a double-sided tape, a double-sided film, a double-sided film, etc.

[0068] In addition, the first adhesive substrate may be an opaque substrate that is difficult to transmit light. Specifically, the first adhesive substrate may have a transmittance of 30% or less in the range of 300 nm to 800 nm in UV-Vis transmittance analysis.

[0069] When the transmittance in the wavelength range corresponding to visible light (in other words, 300nm to 800nm) is 30% or less, the material present on the first adhesive substrate can be easily identified with the naked eye or a microscope, regardless of the color or chromaticity of the substrate. At the same time, the first adhesive substrate preferably has a low transmittance in the visible light region, so as to visually check whether the survey object sample is uniformly captured on the surface, and to check the presence or shape of magnetic foreign matter selectively captured inside the substrate assembly of the first adhesive substrate and the second adhesive substrate after manufacturing the substrate assembly. In addition, when the first adhesive substrate has a low transmittance in the visible light region, magnetic foreign matter attached to the surface of the magnetic member can be easily hidden before the first adhesive substrate is set on the magnetic member, thereby further improving the accuracy and reliability of the magnetic foreign matter analysis results.

[0070] Therefore, the first bonding substrate can have a transmittance of 30% or less in the range of 300nm to 800nm, and more specifically, it can be 25% or less, 20% or less, 15% or less, 10% or less, 5% or less, greater than 0% and less than 30%, 5% to 30%, 5% to 20%, or 5% to 15%.

[0071] In addition, the first adhesive substrate can be a dye dispersed in a resin such as cellulose, polyethylene, polypropylene, poly(ethylene-propylene), poly(ethylene-propylene), polyimide, polyacrylate, etc. to meet the above transmittance, but there is no particular limitation as long as the material is not affected by magnetism.

[0072] In addition, the first adhesive substrate can have an appropriate thickness so that the magnetic force of the magnetic member can be applied to the magnetic foreign matter of the survey object sample captured on the surface. Specifically, the first adhesive substrate can be 5μm to 200μm, and more specifically, it can be 5μm to 150μm, 5μm to 120μm, 5μm to 100μm, 10μm to 120μm, 20μm to 90μm, 50μm to 100μm, or 30μm to 80μm. The present invention can uniformly realize the magnetism of the magnetic element on the surface of the first adhesive substrate by adjusting the average thickness of the first adhesive substrate to the above range. Therefore, when the survey object sample and the magnetic member are mixed, the magnetic foreign matter included in the survey object sample can be captured on the surface of the first adhesive substrate before the non-magnetic substance.

[0073] Next, removing the non-magnetic substances S2 among the sample of the subject of investigation captured on the surface of the first adhesive substrate refers to a process in which the magnetic foreign matter among the sample of the subject of investigation captured by the adhesion of the first adhesive substrate is maintained in a captured state by the magnetic force of the magnetic member by cleaning the surface of the first adhesive substrate, and the non-magnetic substances such as electrode active materials and non-magnetic non-metallic materials are separated from the surface. The present invention can selectively capture only the magnetic foreign matter to be analyzed on the surface of the magnetic member through this process.

[0074] In this case, the non-magnetic material may include a non-metallic material that is not affected by the magnetism of the magnetic member, and in some cases, it may include a metallic material or a diamagnetic or semi-ferromagnetic material that is less affected by the magnetism of the magnetic member.

[0075] In addition, cleaning can be performed by a predetermined cleaning solution. Specifically, the cleaning solution may include water and / or an alcohol having a carbon number of 1 to 4, such as methanol, ethanol, etc. Here, water may be industrial water that does not contain impurities such as metals / metal ions affected by magnetic components and non-metallic solid particles, microorganisms, organic matter, etc. In particular, water may be distilled water purified by at least one distillation process, ion exchange, and / or reverse osmosis.

[0076] In addition, the cleaning can be performed by controlling the spraying speed of the cleaning solution so that the electrode active material and the non-magnetic material are dissociated from the first bonding substrate, or by filling a separate reactor with a cleaning solution and immersing the magnetic member therein and shaking / stirring. In some cases, the cleaning can be performed by dissolving the bonding / bonding layer on the bonding surface of the first bonding substrate that captures the electrode active material and the non-magnetic material with the cleaning solution, selectively retaining only the magnetic foreign matter on the first bonding substrate.

[0077] Next, manufacturing the substrate assembly S3 refers to a process of forming a substrate assembly that attaches the second adhesive substrate to the surface of the first adhesive substrate, wherein only magnetic foreign matter is retained on the surface. In this process, the magnetic foreign matter is fixed at the bonding interface of the first adhesive substrate and the second adhesive substrate, and the bonding interface does not include any magnetic foreign matter other than the magnetic foreign matter collected from the survey subject sample.

[0078] Conventional magnetic foreign matter analysis using a magnetic member has the following limitations: magnetic foreign matter attached to the surface of the magnetic member before analyzing the survey object sample and additional magnetic foreign matter generated during the analysis process exist on the surface of the magnetic member, and therefore, the analysis reliability of the magnetic foreign matter included in the survey object sample is not high.

[0079] However, the substrate assembly of the present invention is capable of capturing magnetic foreign matter using a first adhesive substrate that is capable of hiding the magnetic foreign matter on the surface of the magnetic member before analyzing the survey object sample, and at the same time, using a second adhesive substrate that is easy to transmit light to fix the captured magnetic foreign matter on the first adhesive substrate, while preventing additional magnetic foreign matter generated during the analysis process from being captured on the first adhesive substrate. Therefore, the present invention is characterized in that only magnetic foreign matter included in the survey object sample can be selectively captured and analyzed, and therefore the accuracy and reliability of the analysis result are extremely high.

[0080] For this reason, the second adhesive substrate can be a substrate having an adhesive surface on one side and a non-adhesive surface on the other side. Such a second adhesive substrate can be a single-sided adhesive tape, a single-sided adhesive film, a single-sided adhesive sheet, etc. The second adhesive substrate can be arranged so that the adhesive side is bonded to the first adhesive substrate.

[0081] In addition, the second adhesive substrate can have excellent transmittance for analyzing magnetic foreign matter. For example, the second adhesive substrate can have a transmittance of 70% or more in the range of 300nm to 800nm ​​in UV-Vis transmittance analysis, and more specifically, can have a transmittance 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%.

[0082] The second bonding substrate has an advantage of exhibiting high light transmittance in the wavelength range corresponding to visible light (in other words, from 300 nm to 800 nm), thereby facilitating acquisition of an optical image of the substrate assembly using an optical microscope utilizing visible light.

[0083] Next, separating the substrate assembly S4 refers to a process of separating the substrate assembly in which the first adhesive substrate and the second adhesive substrate are bonded from the magnetic member to prepare a sample for analyzing magnetic foreign matter captured inside the substrate assembly.

[0084] In this case, the substrate component separated from the magnetic member may have foreign matter (e.g., magnetic foreign matter and non-magnetic foreign matter, etc.) generated during the manufacturing process of the substrate component present on the surface. Among these, the foreign matter present on the surface of the second adhesive substrate may serve as a factor that increases the error of the analysis result when performing analysis on the substrate component. Therefore, this step S4 may also perform a process of cleaning the surface of the substrate component after separating the substrate component from the magnetic member in order to improve the accuracy of the analysis result.

[0085] Cleaning can be performed by a predetermined cleaning solution. Specifically, the cleaning solution may include water and / or an alcohol having a carbon number of 1 to 4, such as methanol, ethanol, etc. Here, the water may be industrial water that does not contain impurities such as metals / metal ions affected by magnetic components and non-metallic solid particles, microorganisms, organic matter, etc. In particular, the water may be distilled water purified by at least one distillation process, ion exchange, and / or reverse osmosis, etc.

[0086] Next, analyzing the magnetic foreign matter S5 includes performing analysis on the substrate assembly separated from the magnetic member to analyze at least one of the number and size of the magnetic foreign matter captured at the interface of the first bonding substrate and the second bonding substrate.

[0087] Here, the analysis may include spectral analysis and optical image analysis of the substrate component. Specifically, S5 may be performed in the following manner:

[0088] deriving a shadow map of the surface of the substrate component represented on the pixel unit from the secondary light generated by irradiating the surface of the separated substrate component with light, and performing shadow analysis on the derived shadow map to calculate at least one of the number and size of magnetic foreign matter entrained in the substrate component (S5-1),

[0089] respectively obtaining optical images of the surfaces of the substrate components, and reading the presence of magnetic foreign matter from the obtained optical images (S5-2); and

[0090] The calculated value S5-3 from the shadow analysis is verified based on the reading of the optical image.

[0091] Here, S5-1 refers to performing spectral analysis on the substrate component separated from the magnetic member to derive a shadowgram, and analyzing shadows of the shadowgram to calculate at least one of the number and size of magnetic foreign matter.

[0092] Spectral analysis refers to a method of irradiating the surface of a substrate component with light satisfying a predetermined wavelength and obtaining and analyzing secondary light generated by magnetic foreign matter inside the substrate component. Therefore, spectral analysis can be performed on the exposed surface of the second bonding substrate with high light transmittance in the substrate component so that the irradiated light can encounter the magnetic foreign matter.

[0093] In addition, the spectral analysis includes scanning the surface of the second bonding substrate of the substrate assembly to derive the shadow map element by element. The scanning can be performed on the entire surface of the second bonding substrate to be analyzed, and the surface width of the second bonding substrate can be adjusted to a predetermined range. In addition, the scanning is completed by irradiating light satisfying a predetermined wavelength to a predetermined point on the surface of the second bonding substrate and sequentially performing a series of processes to obtain the second light generated thereafter.

[0094] Here, the device for irradiating light that meets a predetermined wavelength (such as the size of the light irradiation tip) can determine the width of the light irradiated on the surface of the second bonding substrate. The width of the light can be a reference for imaging the scanned second light when forming a shadow map, and can be expressed in pixels. For example, if the light irradiation tip of the spectroscopic instrument has a diameter of 30μm and the surface width of the second bonding substrate is 15mm wide × 15mm long, one pixel of the derived shadow map has a resolution of 30μm, and the shadow map can be expressed as 500 pixels wide × 500 pixels long.

[0095] At the same time, the light irradiated onto the surface of the second adhesive substrate can be light for detecting magnetic foreign matter conventionally used in the art. Specifically, the light can be gamma rays (γ rays), x-rays (X-rays), ultraviolet (UV), visible light, infrared (IR), electromagnetic waves, etc. In addition, the spectral analysis can be performed by a method that can use the above light to analyze trace substances. For example, the spectral analysis can be an X-ray fluorescence analysis (XRF), in which fluorescent X-rays are obtained as secondary light. The advantage of X-ray fluorescence analysis (XRF) is that even very small amounts of foreign matter can be accurately analyzed by elemental composition.

[0096] In addition, the shadow map derived above may be expressed in one or more of saturation, color, and brightness, and may be applied on a pixel unit basis, depending on the sensitivity of the secondary light obtained at the time of scanning, by a predetermined software or program, etc. Color refers to chromatic and non-chromatic colors, chromaticity refers to the darkness or brightness of chromatic colors, and brightness refers to the brightness of non-chromatic colors.

[0097] In one example, the shadow map can be represented with an adjusted brightness on a pixel unit according to the sensitivity of the secondary light obtained when represented in a non-color. In this case, the shadow map can be represented as a white or near-white color, where the pixel representing the corresponding point has a high brightness when the sensitivity of the secondary light is high. On the other hand, when the sensitivity of the secondary light is low, the shadow map can be represented as a black or near-black color by achieving a low brightness of the pixel representing the corresponding point.

[0098] As another example, the shadow map may be represented by a color adjusted on a pixel unit according to the sensitivity of the secondary light obtained when represented in both color and non-color. For example, the shadow map may be represented so that when the sensitivity of the secondary light is high, the color of the pixel representing the corresponding point is yellow, as shown in FIG. Figure 3 On the other hand, the shadow map may be represented as red, where the color of the pixel representing the corresponding point is different from yellow when the sensitivity of the secondary light is low.

[0099] The shadow map may be subjected to shadow analysis to identify magnetic foreign objects, and quantification of the identified magnetic foreign objects may produce at least one of a number and a size. Specifically, shadow analysis may refer to grouping pixels in the mapped shadow map that meet predetermined conditions based on sensitivity to secondary light, and quantifying the grouped areas as magnetic foreign objects. In this case, the preset conditions may be conditions of one or more of chromaticity, color, and brightness depending on the representation method of the shadow map. For example, when the pixels of the shadow map are represented by the CIE LAB colorimetric system, if the distance between adjacent pixels is , and If the deviation satisfies a predetermined range, the pixels can be identified and grouped into the same area, and if the deviation is greater than the predetermined range, the pixels can be identified and grouped into different areas.

[0100] As an example, when each pixel in the shadow map is represented by the CIE LAB colorimetric system, if the distance between adjacent pixels is , and / or If the deviation between adjacent pixels is 10 or less, 5 or less, 3 or less, or 1 or less, the pixels can be identified as the same region and grouped together. , and If the deviation is greater than 10, greater than 5, greater than 3, or greater than 1, they can be identified as different regions and are not grouped together.

[0101] As another example, when each pixel in the shadow map is represented by the CIE LAB colorimetric system, the pixels may be identified as the same region and grouped together if the ΔE deviation of each pixel is less than or equal to 10, less than or equal to 5, less than or equal to 3, or less than or equal to 1. 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, they may be identified as different regions and not grouped together.

[0102] In this way, grouping the pixels of the shadow map by shadow analysis can identify the grouped pixels as magnetic foreign matter and quantify the number and / or size of the identified areas. In this case, the quantification can be calculated using the number of pixels in the specified area and the resolution of each pixel.

[0103] Furthermore, S5-2 above refers to respectively obtaining and analyzing the optical image of the surface of the substrate assembly (specifically, the second bonding substrate surface) after the spectral analysis.

[0104] Optical images are obtained using Figure 4The image is obtained by an optical microscope shown, wherein the optical microscope can be applied without limitation as long as it can obtain a magnified image of the surface of a sample using visible light.

[0105] Analyzing the optical image means reading the presence of magnetic foreign matter by observing whether a particle shape satisfying a predetermined size exists in the obtained optical image.

[0106] Conventional scanning electron microscopes (SEM) or transmission electron microscopes (TEM) have been used to obtain images of samples. The present invention utilizes an electron beam to image the interaction of the electron beam with the sample, but the magnetic foreign matter in the present invention has a trapped form surrounded by the bonding substrate, making it difficult to interact directly with the electron beam. On the other hand, an optical microscope using visible light can intuitively determine the shape of the magnetic foreign matter trapped inside the substrate assembly, and thus the presence of the magnetic foreign matter can be easily read.

[0107] In addition, magnetic foreign matter that usually causes undervoltage problems or internal short circuits in secondary batteries may meet a predetermined size. In other words, magnetic foreign matter smaller than a predetermined size is less likely to cause undervoltage problems or internal short circuits. In addition, it is difficult to completely remove magnetic foreign matter present in the electrode active material in practice. Therefore, the magnetic foreign matter read in the optical image may have a particle shape that meets a predetermined size, and a particle shape smaller than a predetermined size may be read as having no magnetic foreign matter present in the substrate assembly. In this case, the magnetic foreign matter to be read may be particles having an average size of 10μm or more, and more specifically, may be particles having an average size of 15μm or more, 20μm or more, 25μm or more, 30μm or more, 35μm or more, 40μm or more, 10μm-200μm, 20μm-200μm, 30μm-200μm, 40μm-200μm, 10μm-150μm, 10μm-100μm, 20μm-100μm, 20μm-80μm, 20μm-60μm.

[0108] Finally, the above S5-3 refers to the process of verifying the calculated value from the shadow analysis based on the reading result of the optical image.

[0109] Since the value calculated by the shadow analysis of the shadow map is calculated based on the result of mapping the obtained secondary X-ray sensitivity, it may not reflect the condition of the size of the magnetic foreign matter. Therefore, it is desirable to verify the shadow analysis output by reflecting the result read from the optical image.

[0110] Therefore, in S5-3 of the present invention, if it is read that there is no magnetic foreign matter at a predetermined position of the optical image, the calculated value from the shadow analysis at the corresponding position of the shadow map can be judged as a noise point. And if the magnetic foreign matter is read as existing at a predetermined position of the optical image, the calculated value from the shadow analysis can be verified by comparing the shape of the magnetic foreign matter read in the optical image with the shape of the grouped area at the corresponding position of the shadow map.

[0111] More specifically, the verification can include identifying locations in the optical image where magnetic particles are read and corresponding locations in the shadow map, and individually verifying that the shadow outputs at corresponding locations in the shadow map are the same magnetic particles by comparing the shape of the identified magnetic particles at each location in the optical image with the shape of the region of grouped pixels.

[0112] Such verification can be performed on each of the shadowgrams derived for each element, and the magnetic particles identified in each shadowgram can be determined to be magnetic particles composed of the element. For example, verification can be performed by comparing a shadowgram derived by performing spectroscopic analysis on iron (Fe) on the same substrate component with a separately obtained optical image, wherein the verified magnetic particles can be magnetic particles including iron (Fe).

[0113] The advantage of the present invention is that, by having the above-mentioned configuration, only the magnetic foreign matter present inside the sample of the investigation object can be selectively analyzed, so that the reliability of the analysis result is high, and the number and / or size of the magnetic foreign matter can be easily analyzed with high accuracy using a shadow map and an optical image representing the surface of the substrate component including the magnetic foreign matter on the pixel unit.

[0114] Hereinafter, the present invention will be described in more detail through examples and experimental examples.

[0115] However, the following examples and experimental examples are merely examples of the present invention, and the present invention is not limited to the following examples and experimental examples.

[0116] Examples 1 and 2 and Comparative Examples 1 and 2. Analysis of Magnetic Foreign Matter in Electrode Active Materials

[0117] By adding 200 g LiNi 0.6 Co 0.2 Mn 0.2 O2, positive electrode active material and 25 mg of a particle having an average particle diameter (D 50 ) of iron particles and stirring to prepare the survey subject sample.

[0118] Then, a permanent magnet in the form of a square column (about 2 cm wide x 2 cm long x 2 cm high) is prepared as a magnetic member, and the permanent magnet is placed in a reactor and mixed with the sample under investigation while stirring (S1). At this time, the permanent magnet has a double-sided tape attached to its surface as a first adhesive substrate, and the adhesion of the double-sided tape is adjusted as shown in Table 1 below. In addition, the double-sided tape has a light transmittance of about 20% to 22% in the 300nm to 800nm ​​wavelength region and has an average thickness of 50μm to 60μm.

[0119] Then, the permanent magnet with the survey object sample captured on its surface is taken out from the reactor and cleaned with reverse osmosis purified water to dissociate non-magnetic materials such as positive electrode active materials from the surface of the double-sided tape (S2).

[0120] A substrate assembly (S3) having magnetic particles fixed at a bonding interface of the double-sided tape and the single-sided tape is prepared by attaching a single-sided tape to a double-sided tape from which a non-magnetic material has been removed. At this time, the attachment of the single-sided tape is adjusted as shown in Table 1 below. In addition, the single-sided tape has a light transmittance of about 88-95% in a wavelength region of 300-800 nm.

[0121] The prepared substrate assembly is separated by dissociation from the permanent magnet ( S4 ), and the surface of the separated substrate assembly is cleaned with reverse osmosis purified water.

[0122] The substrate assembly is then fixed to the sample portion of the XRF spectrometer so that the X-rays can be irradiated onto the second bonded substrate surface. Then, after the fixed second bonded substrate surface is irradiated with X-rays, the surface of the substrate assembly is spectrally analyzed by a mapping scanning method, in which the second X-rays generated at the irradiation point are obtained, and a series of processes are sequentially performed to create a shadow map on a unit pixel according to its sensitivity. At this time, the resolution and scanning speed of the above-mentioned XRF spectrometer are 30μm / pixel and 5ms, respectively. In addition, the total area of ​​the scanned substrate assembly is set to 15mm wide × 15mm long. In addition, a shadow map is created for each element of iron (Fe), nickel (Ni), cobalt (Co), manganese (Mn), chromium (Cr), zinc (Zn), titanium (Ti) and copper (Cu), so that the pixel has a color deviation depending on the sensitivity of the obtained secondary light. Shadow analysis of the shadow map is performed to calculate the number and size of magnetic foreign matter (S5-1). Specifically, if the ΔE deviation of each pixel expressed by the CIE LAB colorimetric system is 3 or less, each pixel of the shadow map is identified as the same area, the pixels are grouped, and the grouped areas are judged to be magnetic foreign matter. The number of areas determined to be magnetic foreign matter and their corresponding sizes are quantified.

[0123] Then, an optical image is obtained from the second bonding substrate surface of the substrate assembly fixed to the sample portion using an optical microscope separately provided in the XRF spectrometer. At this time, the optical microscope has a minimum resolution of 15 μm to 22 μm. The shape of the magnetic foreign matter is read from the obtained optical image based on the presence or absence of a particle shape with an average size of 20 μm (S5-2).

[0124] Based on the reading of the optical image, the previously calculated value is verified (S5-3). Specifically, in the above verification, if it is read that there is no magnetic foreign matter at the predetermined point of the optical image, the calculated value from the shadow analysis at the corresponding point of the shadow map is judged as a noise point. In addition, if the presence of a magnetic foreign matter is detected at a predetermined point in the optical image, the calculated value from the shadow analysis is verified by comparing the shape of the magnetic foreign matter detected in the optical image with the shape of the grouped area at the corresponding position in the shadow map to confirm that it is the same magnetic foreign matter.

[0125] In order to evaluate the accuracy and reliability of the analysis results, the error rate of each analysis result was calculated based on the number and average size of the iron particles included in the survey object sample. In this case, by finding the average particle diameter (D 50 The number of iron particles included in the survey object sample was calculated based on the volume of 1 iron particle of ②25 mg and the volume of the iron particle of ②25 mg, and the error rate was calculated based on the calculated number of iron particles. The results are shown in Table 1 below.

[0126] [Table 1]

[0127]

[0128] As shown in Table 1 above, it was confirmed that the magnetic foreign matter method according to the present invention had a remarkably low error rate of less than ±5% with respect to the number and size of magnetic foreign matter included in the survey subject sample.

[0129] From these results, it can be seen that the magnetic foreign matter method according to the present invention can analyze the amount and size of magnetic foreign matter included in the electrode active material with high accuracy and high reliability.

[0130] As described above, the present invention has been described in more detail by the drawings and embodiments. However, since the configuration described in the drawings or embodiments described herein is only an embodiment of the present invention and does not represent the overall technical spirit of the present invention, it should be understood that the present invention covers various equivalents, modifications and substitutions when the present application is submitted.

[0131] Therefore, the technical scope of the present invention is not limited to the detailed description of the specification but should be determined by the claims of the patent.

[0132] [Description of reference number]

[0133] 10: Substrate components

[0134] 100: First bonding substrate

[0135] 200: Second bonding substrate

[0136] 300: Magnetic foreign matter collected from electrode active materials

[0137] AF: The side in contact with the magnetic member

[0138] IF: One side of the analysis

Claims

1. A method for analyzing magnetic foreign matter, comprising: capturing the sample under investigation on the first adhesive substrate by mixing the sample under investigation including an electrode active material with a magnetic member having a first adhesive substrate provided on the surface thereof (S1), removing non-magnetic material by cleaning the surface of the first adhesive substrate on which the survey object sample is captured (S2), manufacturing a substrate assembly by attaching a second bonding substrate to the surface of the first bonding substrate from which the non-magnetic material has been removed (S3), separating the substrate assembly from the magnetic member (S4); as well as The separated substrate assembly is analyzed to analyze at least one of the number and size of magnetic foreign matter entrained in the substrate assembly ( S5 ).

2. The method for analyzing magnetic foreign matter according to claim 1, wherein: The first adhesive substrate has a transmittance of 30% or less in a range from 300 nm to 800 nm when UV-Vis transmittance is analyzed.

3. The method for analyzing magnetic foreign matter according to claim 1, wherein: The second adhesive substrate has a transmittance of 70% or more in a range from 300 nm to 800 nm when UV-Vis transmittance is analyzed.

4. The method for analyzing magnetic foreign matter according to claim 1, wherein: Analyzing the magnetic foreign matter (S5) is performed by the following steps: Calculating at least one of the number and the size of magnetic foreign matter captured in the substrate component by irradiating light onto the surface of the separated substrate component, deriving a shadow map representing the surface of the substrate component in pixel units from the generated secondary light, and performing shadow analysis of the derived shadow map (S5-1), reading the presence of the magnetic foreign matter in the optical image of the surface of the substrate assembly obtained alone (S5-2); and The calculated value from the shadow analysis is verified based on the reading result of the optical image (S5-3).

5. The method for analyzing magnetic foreign matter according to claim 4, wherein: The shadow map is a pixel cell representation of one or more of color, chromaticity, and brightness that depends on the sensitivity of the secondary light.

6. The method for analyzing magnetic foreign matter according to claim 4, wherein: The shadow analysis calculates at least one of the number and / or size of magnetic foreign matter by grouping pixels in the shadow map that meet preset conditions and quantifying the grouped areas.

7. The method for analyzing magnetic foreign matter according to claim 4, wherein: The shadowgrams are obtained by X-ray fluorescence (XRF).

8. The method for analyzing magnetic foreign matter according to claim 4, wherein: Optical image reading is performed on particles having an average size of 10 μm or more.

9. The method for analyzing magnetic foreign matter according to claim 4, wherein: Verifying the calculated values ​​from the shadow analysis (S5-3) is performed by: If it is read that the magnetic foreign matter does not exist at the predetermined point of the optical image, the calculated value at the corresponding point of the shadow image is determined to be a noise point; as well as If the magnetic foreign matter is read to exist at a predetermined point of the optical image, the calculated value is verified by comparing the shape of the magnetic foreign matter read in the optical image with the shapes of the grouped areas at corresponding positions of the shadow map.

10. The computational magnetic foreign matter analysis method according to claim 1, wherein: After the substrate assembly is separated from the magnetic component ( S4 ), the method further includes cleaning the surface of the substrate assembly.

11. The computational magnetic foreign matter analysis method according to claim 1, wherein: The survey subject samples have a weight of 50 g to 500 g.

12. The computational 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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