Analysis system and analysis method for foreign substances in cathode material

Abstract

The present invention relates to an analysis system and an analysis method for foreign substances in a cathode material, and the analysis system for foreign substances in a cathode material, according to the present invention, comprises: a pretreatment unit for preparing a monolayer sample of a cathode material powder; a measurement unit for obtaining the optical image of the monolayer sample by using an optical microscope; and an analysis unit, which analyzes the optical image of the monolayer sample, thereby obtaining information about foreign substances in the cathode material.

Description

Foreign matter analysis system and method in anode materials

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0085370, filed June 30, 2023, the entire contents of which are incorporated herein by reference.

[0002]

[0003] The present invention relates to a foreign matter analysis system and a foreign matter analysis method in a cathode material, and more particularly, to a foreign matter analysis system and a foreign matter analysis method capable of quantitatively analyzing the shape and composition of low-voltage-induced foreign matters existing in a cathode material.

[0004] The lithium-ion battery production process involves a variety of manufacturing processes, each of which presents various defects that can impact battery performance. Among these, defects caused by foreign matter in raw materials are not only frequent but also require the disposal of finished batteries, resulting in significant quality costs. Furthermore, even when there are no equipment issues, there is a risk of receiving raw materials contaminated with foreign matter from suppliers. Therefore, an effective method for detecting these defects is essential.

[0005] The types of defects caused by foreign matter mixed in vary depending on their properties and size. For example, large foreign matter can tear the separator during rolling, causing a short circuit defect due to direct contact between the anode and cathode, and non-conductive foreign matter can increase internal resistance and reduce maximum output. However, problems caused by these foreign matters can be relatively easily identified during the activation process. However, metallic foreign matter in the cathode material becomes ionized in the electrolyte as the charge and discharge cycles are repeated and recrystallize in the pores of the separator or the cathode, making it difficult to immediately detect the defect. Consequently, recrystallized foreign matter increases the self-discharge rate during battery storage before shipment and causes low-voltage defects, such as rapid voltage drops.

[0006] Previously, inductively coupled plasma (ICP) or X-ray fluorescence (XRF) methods were mainly used to detect metallic foreign substances in positive electrode materials. However, although ICP-AES has the advantage of being able to detect trace amounts of foreign substances in the ppm range, it is difficult to confirm the shape of the foreign substances, making it difficult to identify the source of the foreign substances. In addition, there is a problem that low voltage occurs even when using active materials that have passed quality inspection on the COA (Certificate Of Analysis). On the other hand, XRF has the advantage of being able to analyze a large amount of active materials, but it is difficult to detect foreign substances below a certain size (< 40 ㎛).

[0007] Recently, a detection method using SEM-EDS (Scanning Electron Microscope-Energy Dispersive Spectroscopy) has been attempted, which can detect fine particles as well as confirm the shape and composition, but it has the disadvantage of being difficult to apply industrially because it takes a lot of time for large-area measurement.

[0008] Therefore, a new method for analyzing foreign matter in a cathode material that can detect the shape and composition of metallic foreign matter with a size of 40㎛ or less within a short period of time is required.

[0009] The present invention is intended to solve the above problems, and to provide a cathode material foreign matter analysis system and analysis method capable of quickly detecting the shape and composition of fine metallic foreign matters present in cathode material powder.

[0010] In one aspect, the present invention provides a system for analyzing metallic foreign matter in a cathode material, comprising: a preprocessing unit for preparing a monolayer sample of cathode material powder; a measuring unit for obtaining an optical image of the monolayer sample using an optical microscope; and an analyzing unit for analyzing the optical image of the monolayer sample to obtain information on foreign matter in the cathode material, wherein the preprocessing unit includes a substrate on which the cathode material powder is applied and a first member for removing a portion of the cathode material powder applied on the substrate so that cathode material particles are distributed in a monolayer.

[0011] In another aspect, the present invention provides a method for analyzing metallic foreign matter in a cathode material, comprising: a first step of preparing a monolayer sample by applying cathode material powder on a substrate and then removing a portion of the applied cathode material powder; a second step of obtaining an optical image of the monolayer sample using an optical microscope; and a third step of analyzing the optical image of the monolayer sample to obtain information on foreign matters in the cathode material.

[0012] In another aspect, the present invention provides an optical microscope comprising: a light source; a charge-coupled device (CCD) camera positioned below the light source for capturing an optical image of a sample; a lens unit positioned below the CCD camera for magnifying an image of the sample; a mounting unit positioned below the lens unit for placing a sample; a driving unit for moving the mounting unit and the lens unit; and a polarizing unit positioned between the light source and the CCD camera for removing diffusely reflected light of the sample.

[0013] The system and method for analyzing metallic foreign matter in a cathode material according to the present invention analyze an optical image obtained using an optical microscope to detect metallic foreign matter having a different color and brightness from the cathode active material. By using the system and method of the present invention, shape information of metallic foreign matter having a size of 40㎛ or less can be obtained in a shorter time than in the past.

[0014] In addition, when a laser light source is attached to an optical microscope, information on the composition of the metallic foreign matter can be obtained by analyzing the line spectrum emitted when the detected metallic foreign matter is destroyed by irradiating the laser on the metallic foreign matter.

[0015] In this way, by using the system and analysis method for analyzing metallic foreign matter in a cathode material according to the method of the present invention, it is possible to obtain information on the shape and composition of metallic foreign matter in a cathode material that was not analyzed by existing methods, and thus, foreign matter in a cathode material can be effectively managed, thereby suppressing the occurrence of defects such as low voltage phenomena.

[0016] Figure 1 is a drawing illustrating a process for manufacturing a single-layer sample according to a first embodiment of the present invention.

[0017] FIG. 2 is a drawing illustrating a process for manufacturing a single-layer sample according to a second embodiment of the present invention.

[0018] Figure 3 is a drawing showing the difference in optical images depending on the light source irradiation method of the optical microscope.

[0019] Figure 4 is a diagram showing spectrum data according to the light source irradiation method of an optical microscope.

[0020] Figure 5 is a drawing showing the difference in optical images depending on whether or not a polarizing section of an optical microscope is included.

[0021] Figure 6 is a drawing showing the results of detecting metallic foreign substances according to the present invention.

[0022] Figure 7 is a drawing showing an optical image of a sample manufactured using a flexible substrate and a sample manufactured using carbon tape.

[0023] Figure 8 is a drawing showing an optical image (A) of a sample manufactured by applying positive electrode powder on an adhesive substrate and then removing upper particles with a desorption agent, and an optical image (B) of a sample manufactured by applying positive electrode powder on an adhesive substrate and then not going through a particle removal process using a desorption agent.

[0024] Figure 9 is a drawing showing the results of analyzing the components of metallic foreign matter using a laser.

[0025] Figure 10 is a drawing showing the structure of an optical microscope according to the present invention.

[0026] Hereinafter, the present invention will be described in detail.

[0027] Analysis system

[0028] First, a system for analyzing metallic foreign matter in a cathode material according to the present invention is described.

[0029] The analysis system according to the present invention is for analyzing metallic foreign substances contained in a cathode material, and includes (1) a preprocessing unit, (2) a measurement unit, and (3) an analysis unit.

[0030] The type of cathode material powder to be measured is not particularly limited, and may be various cathode material powders used in the secondary battery field. The cathode material powder may contain metallic foreign substances and cathode active material particles.

[0031]

[0032] The type of metallic foreign matter contained in the cathode material powder is not particularly limited, and various metallic foreign matters that may be contained during the cathode material manufacturing process may be included. For example, the metallic foreign matter may include, but is not limited to, one or more selected from the group consisting of Fe, Cr, Cu, and Zn.

[0033] Meanwhile, the type of positive electrode active material particles included in the positive electrode powder is not particularly limited, and may be positive electrode active material particles generally used in the field of secondary battery technology. For example, the positive electrode active material particles may be lithium metal oxide containing one or more metal elements selected from the group consisting of Ni, Co, Mn, and Al, and specifically, Li x Ni a Co b M 1 c M 2 1-a-b-c O 2+y (Here, M 1 It contains at least one of Al and Mn, and the M 2 It may include at least one of Ba, Ca, Zr, Ti, Mg, Ta, Nb, Mo, W, P, Sr, Bi, Zn, Cr, and V, and may be 0.8≤x≤1.2, 0≤a≤1, 0≤b≤1, 0≤c≤1, 0≤y≤2, and preferably 0.8≤x≤1.2, 0≤a≤0.5, 0≤b≤0.5, 0≤c≤0.2, 0≤y≤2.

[0034]

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

[0036]

[0037] (1) Preprocessing section

[0038] The above pretreatment unit is for manufacturing a monolayer sample of cathode material powder, and includes a substrate on which cathode material powder is applied, and a first member that removes a portion of the cathode material powder applied on the substrate so that cathode material particles are distributed in a monolayer.

[0039] In order to obtain particle information using an optical microscope, the particles of the sample to be observed must be evenly dispersed in a monolayer without eclipse or stacking. This is because if particle agglomeration or occlusion occurs in the sample, undetectable foreign substances may be generated. Therefore, in the present invention, a monolayer sample of cathode material powder is prepared through a pretreatment unit. Conventionally, methods such as surface modification for ligands, thin film preparation using Langmuir-Blodgett, and substrate printing (lithography) have been used to prepare monolayer samples for microscopic observation. However, these methods are not suitable for application to cathode material powder, and have the problem of high cost and long time required because special substrates or ligands must be used. Therefore, in the present invention, a monolayer sample of cathode material powder is prepared using a novel system and method, thereby reducing the cost and preparation time of monolayer samples.

[0040]

[0041] According to the first embodiment, in the preprocessing unit, the substrate may be a flexible substrate, and the first member may be a pressure member.

[0042] The above-mentioned flexible substrate is a substrate having an elasticity to the extent that positive electrode powder particles can be embedded in the surface of the substrate when positive electrode powder is applied to the substrate and then pressed by a pressing member. Examples of the flexible substrate include, but are not limited to, a gel pad or Teflon tape.

[0043] Meanwhile, the pressurizing member is intended to pressurize the cathode powder applied on the flexible substrate in one direction to remove particles located in the upper portion of the cathode powder and to allow the cathode particles to be distributed in a single layer on the flexible substrate, and may be a rigid and horizontal member capable of applying a constant external pressure. For example, the pressurizing member may be, but is not limited to, a knife made of glass or ceramic material.

[0044] Meanwhile, the elastic substrate may be attached to a fixed substrate via an adhesive member. The fixed substrate is intended to prevent the elastic substrate from bending when external pressure is applied by a pressure member, and may be, for example, a glass substrate such as a slide glass, but is not limited thereto. Meanwhile, the adhesive member is intended to bond the fixed substrate and the elastic substrate, and may be, for example, a double-sided adhesive tape, but is not limited thereto.

[0045] Fig. 1 is a schematic diagram showing the process of manufacturing a single-layer sample in the preprocessing unit configured as described above. As shown in Fig. 1, after applying the cathode material powder (30) to be measured on the elastic substrate (10A), when the applied cathode material powder is pushed in one direction using a pressing member (20A), the cathode material particles in the upper layer are pushed out by the pressing member and removed, and only the cathode material particles located in the lowest layer are stuck to the surface of the elastic substrate, thereby manufacturing a single-layer sample.

[0046]

[0047] According to the second embodiment, in the preprocessing unit, the substrate may be an adhesive substrate, and the first member may be a detachable member.

[0048] The adhesive substrate may be any substrate having an adhesive strength sufficient to fix the positive electrode powder particles, and its type is not particularly limited. For example, the adhesive substrate may be, but is not limited to, a particle trap or adhesive tape manufactured by JOMESA.

[0049] Meanwhile, the detachable member has lower adhesive strength than the adhesive substrate and is a member capable of removing particles present in the upper layer of the positive electrode powder applied on the adhesive substrate. For example, a DCR roller may be used, but is not limited thereto.

[0050] At this time, the pretreatment unit may further include, if necessary, a pressurizing member that applies pressure so that the applied positive electrode powder is evenly distributed on the adhesive substrate. The pressurizing member may be, for example, a knife made of glass or ceramic material, but is not limited thereto.

[0051] FIG. 2 is a schematic diagram showing the process of manufacturing a single-layer sample in the preprocessing unit configured as described above. As shown in FIG. 2, after the cathode material powder (30) to be measured is applied on the adhesive substrate (10B), when the cathode material powder is spread using a pressing member (not shown), the particles located in the lowest layer in contact with the adhesive substrate (10B) are adhered to the adhesive substrate (10B). Then, when the applied cathode material powder is pushed out using a release member (20B), the cathode material particles in the upper layer are removed by being attached to the release member (20B) with weak adhesive force, and the cathode material particles located in the lowest layer are attached to the adhesive substrate with strong adhesive force and remain, thereby manufacturing a single-layer sample.

[0052]

[0053] (2) Measurement section

[0054] The measuring section is for obtaining an optical image of a single-layer sample, and in the present invention, an optical microscope is used to obtain an optical image of a single-layer sample prepared in the preprocessing section. When conducting foreign matter analysis using an optical microscope as in the present invention, the analysis time can be significantly shortened compared to when using a scanning electron microscope. Specifically, when using a scanning electron microscope, the analysis time can be significantly shortened by 1 cm. 2 The time required to measure an area is approximately 350 hours, but when using an optical microscope, the time required to measure the same area is drastically reduced to approximately 1 hour.

[0055] In addition, since the optical microscope uses visible light as a light source, the metallic foreign matter in the positive electrode material can be identified by using the difference in color and brightness between the positive electrode active material and the metallic foreign matter in the optical image obtained through the optical microscope, and information such as the size and location of the metallic foreign matter can be analyzed by using image analysis software built into or linked to the optical microscope.

[0056] Specifically, the optical microscope may be a digital optical microscope capable of image analysis. Preferably, the digital optical microscope has a progressive scanning method, 16-bit grayscale for each RGB pixel, and can be configured to adjust white balance.

[0057] FIG. 10 illustrates an embodiment of an optical microscope according to the present invention.

[0058] As illustrated in FIG. 10, the optical microscope may include a light source (100), a CCD camera (20) positioned below the light source for capturing an optical image of a sample, a lens unit (30) positioned below the CCD camera for magnifying an image of the sample, a mounting unit (40) positioned below the lens unit for placing a sample, a driving unit (50) for moving the mounting unit and the lens unit, and a polarizing unit (60) positioned between the light source and the CCD camera for removing diffused light of the sample. At this time, the sample may be a single-layer sample of the cathode material powder manufactured in the pretreatment unit.

[0059] At this time, the light source (100) may be, for example, a high-brightness LED including an electronic shutter whose speed can be adjusted within a range of 1 / 60 to 1 / 20000, and preferably capable of coaxial irradiation and ring irradiation. By adjusting the LED output, the speed of the electronic shutter of the light source, and the light source irradiation method, the brightness of the light source can be finely controlled, and through this, the difference in color and brightness (brightness) between the positive active material and the metallic foreign substance can be maximized, thereby obtaining an optical image in which the metallic foreign substance can be clearly identified.

[0060] Figure 3 is a drawing showing the difference in optical images according to the light source irradiation method. (A) is an optical image obtained when the light source is irradiated coaxially, (B) is an optical image obtained when the light source is irradiated ringwise, and (C) is an optical image obtained when the ring irradiation and coaxial irradiation are set at a ratio of 95:5.

[0061] Figure 4 is a drawing showing spectrum data according to the light source irradiation method. (A) is the spectrum data of brightness and color of an optical image obtained when a light source is irradiated in a ring, and (B) is the spectrum data of brightness and color of an optical image obtained when ring irradiation and coaxial irradiation are set at a ratio of 95:5.

[0062] Through Fig. 3, it can be confirmed that the brightness and color of the optical image obtained vary depending on the irradiation method of the light source. Meanwhile, although it appears with the naked eye that the foreign matter is most clearly identified in the ring irradiation method, as shown in Fig. 4, the difference in brightness and color appeared more clearly when the ring irradiation and coaxial irradiation were used together. This is believed to be because the optical image obtained by the ring irradiation method contains too much information, resulting in noise. Therefore, in order to increase the difference in brightness and / or color between the positive electrode active material and the metallic foreign matter, thereby enhancing the ability to identify the metallic foreign matter in the positive electrode material, it is preferable that the light source irradiation method be set to a combination of ring irradiation and coaxial irradiation.

[0063] Next, the CCD camera (20) is used to capture an image of a sample enlarged by a lens unit (30), and may have, for example, a resolution of FHD to 4K. Since the resolution of the CCD camera may be too low to reduce the ability to identify foreign substances, it is preferable to have a resolution higher than FHD.

[0064] Next, the lens unit (30) is used to magnify the image of the sample, and the magnification of the lens unit (30) is preferably 200 to 500 times. If the magnification of the lens unit is too low, it is difficult to identify minute foreign substances, and if it is too high, the area that can be measured at once becomes small, resulting in a longer measurement time.

[0065] Next, the driving unit (50) may include a stepping motor to move the mounting unit (40) where the sample is placed left and right and to move the lens unit (30) up and down. By controlling the driving unit, the mounting unit and the lens unit are moved precisely to focus and capture a sample image.

[0066] Meanwhile, the polarizing unit (60) is intended to maximize the identification of the detection target (e.g., metallic foreign matter) in the optical image by removing reflected light scattered from materials other than the target to be detected (e.g., background and positive active material), and includes an upper polarizing plate (62) arranged on the light source (10) side and a lower polarizing plate (64) arranged on the CCD camera (20) side. In addition, if necessary, the polarizing unit (60) may further include a polarizing filter (66) arranged between the upper polarizing plate (62) and the lower polarizing plate (64).

[0067] At this time, the degree of removal of diffuse light can be controlled by adjusting the polarization axis angle depending on the type of material (e.g., positive electrode active material) contained in the sample other than the detection target. For example, depending on the type of positive electrode active material contained in the positive electrode powder, the polarization axes of the upper and lower polarizing plates can be adjusted to an angle of 30 to 150°.

[0068] Meanwhile, when analyzing a sample with severe diffuse reflection, the identification of the detection target (e.g., metallic foreign matter) in the optical image can be further improved by additionally including a polarizing filter between the upper and lower polarizing plates. At this time, the polarizing filter can be appropriately selected depending on the type of the sample to be measured, and for example, when analyzing a cathode material powder containing lithium nickel cobalt manganese oxide as the cathode active material, the OP-88323 filter from Keyence Co. can be used, but is not limited thereto.

[0069] Fig. 5 is a diagram showing the difference in optical images depending on whether a polarizing part is included. In Fig. 5, (A) is a diagram showing an optical image and spectral data captured using an optical microscope that does not include a polarizing part, and (B) is a diagram showing an optical image and spectral data captured using an optical microscope that includes a polarizing part. At this time, the light sources of (A) and (B) were irradiated in the same manner and under the same conditions.

[0070] Through Fig. 5, it can be confirmed that the identification of metallic foreign matter is improved as the brightness of the active material particles and the background darkens in the optical image taken with an optical microscope including a polarizing part.

[0071] After placing the monolayer sample prepared in the preprocessing section on the mounting section of the optical microscope as described above, the shooting mode such as image setting conditions and color adjustment conditions and the light source irradiation conditions such as light source brightness and irradiation method are appropriately set, and the area to be photographed is designated, and then the driving section is adjusted to focus, and then the sample image is photographed to acquire an optical image. The acquired optical image is transmitted to the analysis section.

[0072] At this time, the above shooting mode can be appropriately adjusted depending on the type of positive electrode powder to be measured. For example, when analyzing positive electrode powder containing lithium nickel manganese cobalt oxide as the positive electrode active material, it can be performed by setting edge intensity, gamma, offset, etc. to OFF in the image settings and setting RGB to the ratio of R:1.78, G:1.00, B:2.29, but it is not limited thereto, and if the type of positive electrode active material changes or the type of metallic foreign matter to be detected changes, the conditions of the shooting mode may also change.

[0073] Meanwhile, the light source irradiation conditions may be appropriately adjusted depending on the type of cathode material powder to be measured. For example, when analyzing cathode material powder containing lithium nickel manganese cobalt oxide as the cathode active material, the light source irradiation conditions may be set to a shutter speed of 35 and a ring (95):coaxial (5) condition, but this is not limited thereto, and the light source irradiation conditions may also be changed if the type of cathode active material or the type of metallic foreign matter to be detected changes.

[0074] Meanwhile, in terms of increasing the detection ability of metallic foreign substances, it is preferable that the photographing be performed at a high magnification of 300 times or more, preferably 400 times or more, and is preferably performed using a depth-up function.

[0075]

[0076] Meanwhile, although not essential, the optical microscope may additionally include a laser light source (70) for analyzing the components of metallic foreign matter. The laser light source (70) may be arranged parallel to the lens unit (30) on the upper portion of the mounting portion, and may be configured to be movable up, down, left, and right. When the optical microscope is equipped with a laser light source, the components of metallic foreign matter can be analyzed through destructive analysis using the laser light source.

[0077] As the above laser light source (70), for example, a class 1 YAG laser can be used, and a wavelength range of 300 nm to 400 nm, for example, 355 nm, can be used, but is not limited thereto.

[0078] In addition, it is preferable that the laser light source has a laser spot size of 5㎛ or more, and that the output is variably controlled.

[0079] Meanwhile, the laser irradiation time may be approximately 1 to 3 seconds, and it is preferable that the laser irradiation be performed under room temperature and pressure conditions.

[0080]

[0081] (3) Analysis Department

[0082] The analysis unit is intended to analyze the optical image acquired from the measurement unit to obtain information on foreign substances within the cathode material, and may include image analysis software built into the optical microscope or linked to the optical microscope. In this case, the image analysis software is preferably capable of performing functions such as automatic area measurement, color and brightness data extraction, and filtering.

[0083] The above analysis unit can extract color and brightness data from an optical image transmitted from a measurement unit, for example, and obtain shape information and location information of a metallic foreign body using the extracted color and brightness data. For example, if the color and brightness values ​​extracted from the optical image satisfy the preset reference color and reference brightness of the foreign body, the foreign body can be recognized as a metallic foreign body, and by storing data such as the location, area, and size of the recognized metallic foreign body, shape information and location information of the metallic foreign body can be obtained.

[0084] Meanwhile, the reference color and reference brightness of the foreign substance can be set by preparing a reference sample by adding a metallic foreign substance to the cathode powder and analyzing the reference sample according to the method of the present invention.

[0085] Meanwhile, the above analysis unit can analyze each high-magnification and depth-synthesized optical image by stitching it.

[0086] Figure 6 shows the results of detecting metallic foreign bodies by analyzing optical images measured at 400x magnification. In Figure 6, (A) is a 1 cm image obtained by stitching multiple optical images. 2This is a stitched image for the area, (B) is an individual optical image taken at 400x magnification, and (C) is an image showing an enlarged area of ​​a metallic foreign particle identified in the optical image. The white area in (B) of Fig. 6 indicates the foreign particle. Through Fig. 6, it can be confirmed that using the analysis system of the present invention, a foreign particle of a microscopic size of 10㎛ or less can be detected, and shape information such as the size of the foreign particle can also be obtained.

[0087]

[0088] Meanwhile, if necessary, the location information of the metallic foreign matter identified in the analysis unit is transmitted to a measurement unit including an optical microscope equipped with a laser light source, and the measurement unit can obtain information on the composition of the metallic foreign matter by irradiating the metallic foreign matter with a laser based on the transmitted location information. Specifically, when the location information of the metallic foreign matter obtained in the analysis unit is transmitted to an optical microscope, the laser light source can irradiate the corresponding location with a laser based on the transmitted location information to burn the metallic foreign matter, and information on the composition of the metallic foreign matter can be obtained through the line spectrum generated in this process.

[0089]

[0090] Analysis method

[0091] Next, a method for analyzing metallic foreign matter in a cathode material according to the present invention is described.

[0092] The method for analyzing metallic foreign matter in a cathode material according to the present invention comprises a first step of preparing a monolayer sample by applying cathode material powder on a substrate and then removing a portion of the applied cathode material powder; a second step of obtaining an optical image of the monolayer sample using an optical microscope; and a third step of obtaining information on foreign matter in the cathode material by analyzing the optical image of the monolayer sample.

[0093] At this time, the cathode material powder may be a variety of cathode material powders used in the secondary battery field, as described above. The cathode material powder may include metallic foreign matter and cathode active material particles. The types of the metallic foreign matter and cathode active material are the same as described above.

[0094] Hereinafter, each step of the method for analyzing metallic foreign matter in a cathode material according to the present invention will be described in detail.

[0095]

[0096] (1) Step 1: Single-layer sample preparation step

[0097] First, a monolayer sample of the cathode material powder is prepared (Step 1). At this time, the monolayer sample preparation can be performed using the following two methods.

[0098] According to the first embodiment, the first step includes: a step of applying a cathode material powder to be measured on a flexible substrate; and a step of using a pressure member to push the cathode material powder applied on the flexible substrate in one direction to remove upper layer particles and form a single layer.

[0099] At this time, the elastic substrate may be attached to a fixed substrate via an adhesive member, and the elastic substrate, the pressure member, the fixed member, and the adhesive member are the same as those described in the preprocessing section, so a detailed description thereof is omitted.

[0100] Referring to Fig. 1, after applying the cathode material powder (30) to be measured on the elastic substrate (10A), when the applied cathode material powder is pushed in one direction using a pressure member (20A), the cathode material particles in the upper layer are pushed out by the pressure member and removed, and only the cathode material particles located in the lowest layer are stuck to the surface of the elastic substrate, thereby producing a single-layer sample.

[0101]

[0102] FIG. 7 shows optical images of samples manufactured using a flexible substrate and samples manufactured using carbon tape. Here, A is an optical image of a sample manufactured by applying cathode material powder onto a gel pad attached to a slide glass using double-sided tape and then pushing it out in one direction with a pressure-resistant glass; B is an optical image of a sample manufactured by applying cathode material powder onto a Teflon tape attached to a slide glass using double-sided tape and then pushing it out in one direction with a pressure-resistant glass; C is an optical image of a sample manufactured by applying cathode material powder onto a non-stretchy carbon tape and then pushing it out in one direction with a pressure-resistant member; and D is an optical image of a sample manufactured by scattering cathode material powder onto a carbon tape to prevent particle agglomeration.

[0103] As shown in Fig. 7, in the case of samples A and B using a flexible substrate, the particles were well dispersed with high particle density and no interference or agglomeration between particles, whereas in the case of sample C, there was agglomeration between particles, which caused problems such as the lowest layer particles being obscured and the carbon tape being damaged when pressurized, and in the case of sample D, the particle density was very low, making it unsuitable for the analysis of metal foreign substances that require analysis of a large amount.

[0104]

[0105] According to a second embodiment, the first step includes a step of applying a cathode material powder to be measured on an adhesive substrate; and a step of removing upper particles of the cathode material powder applied on the adhesive substrate using a detaching member to form a single layer. If necessary, after the step of applying the cathode material powder, the first step may further include a step of applying pressure using a pressing member so that the cathode material powder is evenly distributed on the adhesive substrate.

[0106] At this time, the adhesive substrate, detachment member, and pressure member are the same as those described in the preprocessing section, so a detailed description is omitted.

[0107] Referring to Fig. 2, when the cathode material powder (30) to be measured is applied on an adhesive substrate (10B) and then spread using a pressing member (not shown), the particles located in the lowest layer in contact with the adhesive substrate (10B) are adhered to the adhesive substrate (10B). Then, when the applied cathode material powder is pushed out using a release member (20B), the cathode material particles in the upper layer are attached to the release member (20B) with weak adhesive force and are removed, and the cathode material particles located in the lowest layer are attached to the adhesive substrate with strong adhesive force and remain, thereby producing a single-layer sample.

[0108]

[0109] Figure 8 shows an optical image (A) of a sample manufactured by applying positive electrode powder on an adhesive substrate and then removing upper particles with a desorption agent, and an optical image (B) of a sample manufactured by applying positive electrode powder on an adhesive substrate and then not performing a particle removal process using a desorption agent. In this case, a particle trap was used as the adhesive substrate, and a DCR roller was used as the desorption agent.

[0110] As shown in Fig. 8, in the case of sample A, it was observed that the particles were evenly distributed in a single layer, whereas in the case of sample B, which did not undergo a particle removal process, it was confirmed that the upper layer particles were photographed together, so the lower layer particles were not properly observed and were out of focus.

[0111]

[0112] (2) Step 2: Optical image measurement step

[0113] Next, an optical image of the single-layer sample obtained in the first step is obtained using an optical microscope (step 2).

[0114] At this time, the second step can be performed by adjusting the light source setting and shooting mode of the optical microscope so that the difference in brightness between the positive active material and the metallic foreign material in the optical image increases.

[0115] Specifically, after placing the single-layer sample manufactured in the first step on the mounting section of the optical microscope, the shooting mode (image settings, color adjustment, etc.) and light source settings (brightness, irradiation method, etc.) on the optical microscope are appropriately adjusted, the area to be photographed is specified, the driving section of the optical microscope is adjusted to focus, and then the sample image is photographed to obtain an optical image.

[0116] At this time, it is preferable that the light source setting and shooting mode be adjusted so that the color and brightness difference between the background, the positive active material, and the metallic foreign matter can be maximized in the optical image. For example, the light source is preferably set to a combination of coaxial irradiation and ring irradiation, and more preferably, the ring irradiation: coaxial irradiation can be set to 95:5. When the light source irradiation conditions are set as above, the brightness and color difference between the background, the positive active material, and the foreign matter is clearly shown in the optical image, thereby increasing the foreign matter identification ability (see FIGS. 3 and 4). In addition, if necessary, the electronic shutter speed can be adjusted to control the brightness of the light source. However, the light source setting conditions may vary depending on the type of positive active material to be measured.

[0117] Meanwhile, the above shooting mode can be performed, for example, by setting edge intensity, gamma, offset, etc. to OFF in the image settings and setting RGB to the ratio R:1.78, G:1.00, B:2.29, but is not limited thereto, and can be appropriately adjusted depending on the type of cathode powder to be measured.

[0118]

[0119] (3) Step 3: Optical image analysis step

[0120] Next, the optical image of the single-layer sample obtained through the second step is analyzed to obtain information on foreign substances in the cathode material (third step).

[0121] At this time, the third step may include a step of extracting color and brightness data from an optical image, identifying a metallic foreign body using the extracted color and brightness data, and obtaining shape information and location information of the identified metallic foreign body.

[0122] For example, the identification of the metallic foreign matter can be accomplished by comparing the color and brightness values ​​extracted from the optical image with the reference color and reference brightness of the preset foreign matter, and recognizing the metallic foreign matter when the reference color and reference brightness are satisfied, and by storing data such as the location, area, and size of the recognized metallic foreign matter, shape information and location information of the metallic foreign matter can be obtained. At this time, the reference color and reference brightness of the foreign matter can be set by adding the metallic foreign matter to a cathode powder to prepare a reference sample, and analyzing the reference sample according to the method of the present invention.

[0123] The above analysis can be performed through image analysis software built into or linked to an optical microscope, and it is preferable that the image analysis software be capable of performing functions such as automatic area measurement, color and brightness data extraction, and filtering.

[0124]

[0125] Using the above method, foreign matter of a size of 10㎛ or less can be detected, and shape information such as the size of the foreign matter and location information of the foreign matter can be obtained (see Fig. 6).

[0126]

[0127] Meanwhile, the analysis method according to the present invention may additionally include a step of analyzing the components of the metallic foreign matter, if necessary.

[0128] The above component analysis step may include, for example, a step of transmitting location information of the identified metallic foreign matter to an optical microscope equipped with a laser light source, and a step of obtaining component information of the metallic foreign matter by irradiating the metallic foreign matter with a laser based on the transmitted location information.

[0129] When a laser is irradiated on a metallic foreign body, the metallic foreign body is burned by the laser and a line spectrum is generated. By analyzing the line spectrum, information on the composition of the metallic foreign body can be obtained.

[0130] Meanwhile, in order to prevent measurement errors caused by elements contained in the air, it is desirable to obtain a line spectrum by irradiating the laser in a blank state, and analyze the components of the metallic foreign matter through the line spectrum of the remaining area excluding the area overlapping with the line spectrum obtained by irradiating the laser in a blank state from the line spectrum obtained by irradiating the laser on the metallic foreign matter.

[0131]

[0132] Figure 9 illustrates the results of a laser-based analysis of the components of metallic foreign matter. Specifically, the line spectra measured by irradiating two particles identified as foreign matter through optical image analysis with a laser are shown. As shown in Figure 9, analyzing the line spectra allows for the identification of the components of the corresponding particles.

Claims

1. Pretreatment section for manufacturing a monolayer sample of positive electrode powder; A measuring unit for obtaining an optical image of the single-layer sample using an optical microscope; and It includes an analysis unit that analyzes the optical image of the above-mentioned single-layer sample to obtain information on foreign substances in the cathode material, A system for analyzing metallic foreign matter in a cathode material, wherein the preprocessing unit includes a substrate on which the cathode material powder is applied and a first member that removes a portion of the cathode material powder applied on the substrate so that the cathode material particles are distributed in a single layer.

2. In paragraph 1, A system for analyzing metallic foreign matter in a cathode material, wherein the cathode material powder contains metallic foreign matter and cathode active material particles.

3. In paragraph 2, A system for analyzing metallic foreign matter in a cathode material, wherein the metallic foreign matter comprises at least one selected from the group consisting of Fe, Cr, Cu, and Zn.

4. In paragraph 2, A system for analyzing metallic foreign matter in a cathode material, wherein the cathode active material particles are lithium metal oxides containing at least one metal element selected from the group consisting of Ni, Co, Mn, and Al.

5. In paragraph 1, The above substrate is a flexible substrate, A system for analyzing metallic foreign matter in a cathode material, wherein the first member is a pressing member that presses cathode material powder applied on the elastic substrate in one direction to distribute cathode material particles in a single layer on the elastic substrate.

6. In paragraph 5, The above flexible substrate is a gel-pad or Teflon tape, A system for analyzing metallic foreign matter in an anode material, wherein the above-mentioned pressurizing member is made of glass or ceramic material.

7. In paragraph 5, A system for analyzing metallic foreign matter in a cathode material, wherein the above preprocessing unit further includes a fixed substrate to which the elastic substrate is attached via an adhesive member.

8. In paragraph 7, The above fixed substrate is a system for analyzing metallic foreign matter in an anode material which is a glass substrate.

9. In paragraph 1, The above substrate is an adhesive substrate, A system for analyzing metallic foreign matter in a cathode material, wherein the first member has lower adhesive strength than the adhesive substrate and is a detaching member that removes particles present in the upper layer of cathode material powder applied on the adhesive substrate so that cathode material particles are distributed in a single layer on the adhesive substrate.

10. In paragraph 9, The above adhesive substrate is an adhesive tape, The above-mentioned detachable member is a system for analyzing metallic foreign matter in a cathode material, which is a DCR roller.

11. In paragraph 9, A system for analyzing metallic foreign substances in a cathode material, wherein the preprocessing unit further includes a pressing member that pressurizes the cathode material powder so that it is evenly distributed on the adhesive substrate.

12. In paragraph 1, The above optical microscope, Light source (10); A CCD camera (20) located below the light source and capturing an optical image of the sample; A lens unit (30) located below the CCD camera and magnifying the image of the sample; A mounting portion (40) located at the lower portion of the above lens portion and where a sample is placed; A driving unit (50) for moving the above-mentioned positioning unit and lens unit; and A system for analyzing metallic foreign matter in a cathode material, the system including a polarizing part (60) disposed between the light source and the CCD camera and for removing scattered light from the sample.

13. In paragraph 12, A system for analyzing metallic foreign matter in an anode material, wherein the light source is a high-brightness LED including an electronic shutter adjustable within a range of 1 / 60 to 1 / 20000.

14. In paragraph 12, The above light source is a system for analyzing metallic foreign matter in a cathode material capable of co-axial irradiation and ring irradiation.

15. In paragraph 12, The above lens unit is a system for analyzing metallic foreign substances in a cathode material having a magnification of 200 to 500 times.

16. In paragraph 12, A system for analyzing metallic foreign matter in a cathode material, wherein the above driving unit includes a stepping motor.

17. In paragraph 12, The above CCD camera is a system for analyzing metallic foreign matter in a cathode material having a resolution of FHD to 4K.

18. In paragraph 12, A system for analyzing metallic foreign matter in a cathode material, wherein the polarizing unit includes an upper polarizing plate disposed on the light source side and a lower polarizing plate disposed on the CCD camera side.

19. In paragraph 18, A system for analyzing metallic foreign matter in a cathode material, wherein the polarizing unit further includes a polarizing filter disposed between the upper polarizing plate and the lower polarizing plate.

20. In paragraph 12, The above optical microscope is a system for analyzing metallic foreign matter in a cathode material, which additionally includes a laser light source for analyzing the components of metallic foreign matter.

21. In paragraph 20, The above laser light source is a YAG laser, a system for analyzing metallic foreign matter in an anode material.

22. In paragraph 20, The above laser light source is a system for analyzing metallic foreign matter in a cathode material having a laser spot size of 5㎛ or more.

23. In paragraph 20, A system for analyzing metallic foreign matter in a cathode material, wherein the output of the above laser light source is variably controlled.

24. In paragraph 1, A system for analyzing metallic foreign matter in a cathode material, wherein the above analysis unit extracts color and brightness data from an optical image of the single-layer sample, and identifies shape information and location information of the metallic foreign matter using the extracted color and brightness data.

25. In paragraph 24, The above analysis unit transmits the location information of the identified metallic foreign matter to the measurement unit, A system for analyzing metallic foreign matter in a cathode material, wherein the measuring unit obtains information on the composition of the metallic foreign matter by irradiating a laser on the metallic foreign matter based on the transmitted location information.

26. A first step of manufacturing a monolayer sample by applying cathode material powder on a substrate and then removing some of the applied cathode material powder; A second step of obtaining an optical image of the single-layer sample using an optical microscope; and A method for analyzing metallic foreign matter in a cathode material, comprising a third step of obtaining information on foreign matter in the cathode material by analyzing an optical image of the above-mentioned single-layer sample.

27. In paragraph 26, The above first step is, A step of applying a cathode material powder to be measured on a flexible substrate; and A method for analyzing metallic foreign matter in a cathode material, comprising a step of using a pressure member to push cathode material powder applied on the elastic substrate in one direction to remove upper layer particles and form a single layer.

28. In paragraph 27, A method for analyzing metallic foreign matter in a cathode material, wherein the above-mentioned flexible substrate is attached to a fixed substrate through an adhesive member.

29. In paragraph 26, The above first step is, A step of applying a cathode material powder to be measured on an adhesive substrate; and A method for analyzing metallic foreign matter in a cathode material, comprising a step of removing upper particles of cathode material powder applied on the adhesive substrate using a detachable member to form a single layer.

30. In paragraph 26, The second step above is, A method for analyzing metallic foreign matter in a cathode material, which is performed by adjusting the light source setting and shooting mode of an optical microscope so that the difference in color and brightness between the cathode active material and the metallic foreign matter in the optical image increases.

31. In paragraph 30, A method for analyzing metallic foreign matter in a cathode material, wherein the light source is set to a combination of coaxial irradiation and ring irradiation.

32. In paragraph 31, A method for analyzing metallic foreign matter in a cathode material, wherein the light source is set to be 95:5 for ring irradiation: coaxial irradiation.

33. In paragraph 31, The third step is a method for analyzing metallic foreign matter in a cathode material, including a step of extracting color and brightness data from the optical image and identifying shape information and location information of the metallic foreign matter using the extracted color and brightness data.

34. In paragraph 31, The above optical microscope additionally includes a laser light source, The third step above is, A step of transmitting location information of the identified metallic foreign body to an optical microscope equipped with a laser light source, and A method for analyzing metallic foreign matter in a cathode material, further comprising a step of obtaining information on the composition of the metallic foreign matter by irradiating the metallic foreign matter with a laser based on the location information of the transmitted metallic foreign matter.

35. Light source; A CCD camera positioned below the light source and capturing an optical image of the sample; A lens unit located below the CCD camera and magnifying the image of the sample; A mounting portion located at the lower portion of the above lens portion, where a sample is placed; A driving unit for moving the above-mentioned positioning unit and lens unit; and An optical microscope disposed between the light source and the CCD camera and including a polarizing section for removing scattered light from the sample.

36. In paragraph 35, An optical microscope wherein the light source is a high-brightness LED including an electronic shutter adjustable within a range of 1 / 60 to 1 / 20000.

37. In paragraph 35, The above light source is an optical microscope capable of coaxial irradiation and ring irradiation.

38. In paragraph 35, The above lens unit is an optical microscope with a magnification of 200 to 500 times.

39. In paragraph 35, The above driving unit is an optical microscope including a stepping motor.

40. In paragraph 35, The above CCD camera is an optical microscope having a resolution of FHD to 4K.

41. In paragraph 35, An optical microscope, wherein the polarizing section includes an upper polarizing plate placed on the light source side and a lower polarizing plate placed on the CCD camera side.

42. In paragraph 41, An optical microscope, wherein the polarizing unit further includes a polarizing filter disposed between the upper polarizing plate and the lower polarizing plate.

43. In paragraph 35, The above optical microscope is an optical microscope that additionally includes a laser light source for analyzing the components of metallic foreign matter.

44. In paragraph 43, An optical microscope in which the above laser light source is a YAG laser.

45. In paragraph 43, The above laser light source is an optical microscope having a laser spot size of 5㎛ or more.

46. ​​In paragraph 43, An optical microscope wherein the laser light source has a variably controlled output.

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