Pore detection method for electrode plate

Abstract

The invention provides a pore detection method of an electrode plate, and relates to the technical field of electrode plate porosity detection, a gaseous developer is adsorbed or deposited in pores of the electrode plate, the pores of the electrode plate to be detected are calibrated by using the gaseous developer, and the cross section of the electrode plate is treated by an ion beam polishing treatment process. According to the method, the developing agent is taken as a developing agent, then the signal of the developing agent is detected, the pore distribution in the battery pole piece can be observed, the porosity of the pole piece can be calculated, the detection precision is guaranteed, the sample treatment process is greatly simplified, the detection period is remarkably shortened, and powerful technical support is provided for research and quality control of an electrode material.

Description

Technical Field

[0001] The present invention relates to the technical field of electrode sheet porosity detection, and in particular to a porosity detection method for an electrode sheet. Background Art

[0002] In order to meet the requirements of improving battery performance and reducing costs, especially the development of double-layer coating technology, it is necessary to observe and calculate the pore distribution of battery electrodes.

[0003] The prior art CN 116818628 A uses the difference processing analysis of the gray value of the SEM image to obtain a fuzzy pore boundary with a large random error;

[0004] CN 115979907 A utilizes a developing solution to soak the electrode piece for developing calibration, which has a complicated operation process and is easy to cause damage to the electrode piece itself, thus affecting the accuracy of the test result.

[0005] The detection results of the existing methods all have the problem of poor accuracy. In view of this, the present invention is proposed. Summary of the invention

[0006] The purpose of the present invention is to provide a method for detecting the pores of an electrode sheet, which uses a gaseous developer to calibrate the pores of the electrode sheet to be tested, processes the electrode sheet cross section through an ion beam polishing process, and then detects the developer signal, so as to observe the pore distribution in the battery electrode sheet and calculate the electrode sheet porosity.

[0007] In order to achieve the above object, the present invention adopts the following technical solutions:

[0008] The present invention provides a method for detecting the pores of an electrode sheet, comprising the following steps:

[0009] S1: placing the electrode sheet to be tested in a sealed instrument, replacing the gas in the sealed instrument with a gaseous developer, so as to adsorb or deposit the gaseous developer in the pores on the surface of the electrode sheet to be tested;

[0010] S2: transferring the electrode sheet to be tested obtained in step S1 to a transfer container, and then performing ion beam milling to obtain one or more cross sections to be tested;

[0011] S3: performing developer signal detection on the cross section to be tested to obtain the pore distribution of the electrode sheet to be tested, and calculating the electrode sheet porosity through image analysis.

[0012] Further, based on the above technical solution, the gaseous developer includes an inert gas for detecting the gaseous developer signal using SEM-EDS or a fluorescent gas for detecting the gaseous developer signal using a spectral analysis instrument.

[0013] Further, on the basis of the above technical solution, the inert gas includes one or more of argon, neon, helium, xenon, and krypton;

[0014] And / or, the spectral analysis instrument includes one of a fluorescence spectrometer, a Raman spectrometer, and an infrared spectrometer;

[0015] And / or, the fluorescent gas includes one or more of argon, neon, helium, xenon, krypton, benzene derivatives, and naphthalene derivatives.

[0016] Further, on the basis of the above technical solution, in step S1, the sealed instrument is a true density meter or a high-pressure reactor; and the number of times of gas replacement in the sealed instrument is ≥2 times.

[0017] Further, based on the above technical solution, in step S1, after the gas in the sealed instrument is replaced with a gaseous developer, the pressure of the inert gas or fluorescent gas in the sealed instrument cavity is maintained at 1.2-2.0 atm for a period of ≥15 s.

[0018] Further, on the basis of the above technical solution, in step S2, the transfer is to take the electrode sheet out of the sealed instrument and immediately put it into a transfer container with an air pressure of 1-1.2atm;

[0019] And / or, the gas in the transfer container is consistent with the gas in the sealed instrument.

[0020] Further, based on the above technical solution, in step S2, the ion beam milling is performed in an ion beam milling instrument, and the technical parameters of the ion beam milling instrument include:

[0021] The ion gun is a saddle-type ion gun, and the number of ion guns is ≥ 3;

[0022] The ion gun voltage is 1-10 kV;

[0023] The ion gun current is 0.5-4.5mA;

[0024] The maximum ion beam cutting rate is ≥300μm / h.

[0025] Further, on the basis of the above technical solution, in step S3, developer signal detection is performed on the cross section to be tested to obtain the pore distribution of the electrode sheet to be tested, specifically:

[0026] When developer signal detection is performed on a detection area of ​​a section to be tested, the pore distribution of the electrode sheet to be tested is directly obtained according to the detection condition of at least one detection area on the section to be tested;

[0027] Or, when developer signal detection is performed on multiple sections to be tested, the pore distribution of the electrode to be tested is obtained, specifically:

[0028] When developer signal detection is performed on at least one detection area of ​​each of the multiple sections to be measured, the pore distribution of the electrode piece to be measured is obtained by integrating the developer signal detection results of the detection areas of the multiple sections to be measured.

[0029] Further, based on the above technical solution, the image analysis calculation includes:

[0030] The pore distribution image of the electrode sheet to be tested is imported into the image processing software. The software obtains the threshold value according to the obvious grayscale difference between the pores and the coating particles in the pore distribution image, and performs segmentation and marking according to the threshold value to obtain the particle area and the pore area;

[0031] The total number of pixels in the pore area is calculated by difference between the total number of pixels in the particle area and the total number of pixels in the pore distribution image, and the ratio of the total number of pixels in the pore area to the total number of pixels in the pore distribution image is the porosity of the electrode sheet to be tested.

[0032] Furthermore, based on the above technical solution, the standard deviation of the porosity of the electrode sheet is ≤0.41%, and the relative error of the porosity of the electrode sheet obtained by FIB-SEM three-dimensional reconstruction is ≤3.73%.

[0033] The present invention provides a method for detecting the pores of an electrode sheet, which has the following beneficial effects:

[0034] 1. The present invention provides a method for detecting the pores of an electrode sheet, which greatly simplifies the sample processing process while ensuring the detection accuracy, significantly shortens the detection cycle, and provides strong technical support for the research and quality control of electrode materials.

[0035] 2. The present invention can automatically identify and extract pore information through instruments, and generate pore distribution maps with clear boundaries and minimal errors. These images not only intuitively display the pore structure characteristics inside the electrode sheet, but also provide a reliable basis for subsequent data analysis and model building.

[0036] 3. The present invention avoids the steps of soaking in developer in the traditional method, effectively preventing the electrode from being damaged by chemical corrosion or physical stress, and ensuring the accuracy of the test results and the reusability of the electrode. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0038] Figure 1 A schematic flow chart of the pore detection method of the electrode sheet provided by the present invention. DETAILED DESCRIPTION

[0039] In order to make the purpose, technical scheme and advantages of the present invention clearer, the technical scheme in the embodiment of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. The process parameters of the following embodiments that do not specify specific conditions are usually based on conventional conditions.

[0040] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0041] According to a first aspect of the present invention, a method for detecting pores of an electrode sheet is provided. Figure 1 As shown, the following steps are included:

[0042] S1: placing the electrode sheet to be tested in a sealed instrument, replacing the gas in the sealed instrument with a gaseous developer, so as to adsorb or deposit the gaseous developer in the pores on the surface of the electrode sheet to be tested;

[0043] S2: transferring the electrode sheet to be tested obtained in step S1 to a transfer container, and then performing ion beam milling to obtain one or more cross sections to be tested;

[0044] S3: performing developer signal detection on the cross section to be tested to obtain the pore distribution of the electrode sheet to be tested, and calculating the electrode sheet porosity through image analysis.

[0045] In the present invention, the gaseous developer is adsorbed or deposited in the pores on the surface of the electrode sheet to be tested, which means that the gaseous developer is adsorbed or deposited in the pores and / or on the surface of the pores.

[0046] Specifically, when the gaseous developer is an inert gas for gaseous developer signal detection using SEM-EDS, the inert gas is stable in chemical properties and is not easy to react with the electrode sheet, and can be accurately and effectively adsorbed or deposited in the pore structure on the surface of the electrode sheet. Subsequently, through the high-resolution imaging capability of SEM and the analysis function of EDS on elemental composition, the locations rich in inert gas elements in the sample can be observed and identified, and the display of these locations directly corresponds to the pore distribution on the surface of the electrode sheet.

[0047] When the gaseous developer is a fluorescent gas that uses a spectroscopic analyzer to detect the gaseous developer signal, since the fluorescent gas can emit characteristic fluorescence when excited by a light source of a specific wavelength, when these gas molecules are adsorbed or deposited by the pores on the surface of the electrode sheet, the position of the fluorescence signal can be accurately captured through the detection of the spectroscopic analyzer. The position of these fluorescent displays directly indicates the location of the pores, which not only provides the spatial position information of the pores, but also can reflect the depth, size and other characteristic information of the pores through the difference in fluorescence intensity, further enriching the characterization methods of the pore structure.

[0048] As an optional embodiment of the present invention, the gaseous developer includes an inert gas for detecting the gaseous developer signal using SEM-EDS or a fluorescent gas for detecting the gaseous developer signal using a spectral analysis instrument.

[0049] As an optional embodiment of the present invention, the inert gas includes one or more of argon, neon, helium, xenon, and krypton;

[0050] The spectrum analysis instrument includes one of a fluorescence spectrometer, a Raman spectrometer, and an infrared spectrometer;

[0051] The fluorescent gas includes one or more of argon, neon, helium, xenon, krypton, benzene derivatives, and naphthalene derivatives.

[0052] Among them, benzene derivatives or naphthalene derivatives may need to form vapor under specific conditions, such as high temperature, etc. For example, phenol, toluene, naphthol, etc. can generate vapor with fluorescent properties at high temperature.

[0053] As an optional implementation manner of the present invention, in step S1, the sealed instrument is a true density meter or a high-pressure reactor; the number of times the gas in the sealed instrument is replaced is ≥ 2 times (such as 3 times, 4 times, 5 times, etc.).

[0054] As an optional embodiment of the present invention, in step S1, after the gas in the sealed instrument is replaced with a gaseous developer, the pressure of the inert gas or fluorescent gas in the sealed instrument cavity is maintained at 1.2-2.0atm (e.g., 1.3atm, 1.4atm, 1.5atm, 1.6atm, 1.7atm, 1.8atm, 1.9atm, etc.), and the maintenance time is ≥15s (e.g., 18s, 20s, 22s, 24s, 26s, 30s, etc.);

[0055] Specifically, the purpose of controlling the pressure of the inert gas or fluorescent gas in the sealed instrument cavity to be maintained at 1.2-2.0 atm is to allow the inert gas or fluorescent gas to be fully adsorbed or filled in the pores of the electrode sheet;

[0056] If the gas pressure is less than 1.2 atm, the concentration of gas molecules in the pores may be insufficient, causing the gas in the pores to dissipate in the subsequent process, affecting the signal detection of the pores;

[0057] If the gas pressure is greater than 2.0atm, the excessively high gas pressure will increase the impact force of the gas on the surface of the electrode sheet, which may cause physical damage or deformation of the surface of the electrode sheet. In addition, the excessively high gas pressure may also make the distribution of the gas in the pores uneven, forming bubbles or local high-pressure areas, affecting the signal detection of the pores. In addition, the excessively high gas pressure may also have an adverse effect on other components of the ion beam milling instrument.

[0058] As an optional embodiment of the present invention, in step S2, the transfer is to take the electrode sheet out of the sealed instrument and immediately put it into a pre-prepared transfer container, the transfer container has good sealing properties, the air pressure in the transfer container is 1-1.2atm (such as 1.02atm, 1.04atm, 1.06atm, 1.08atm, 1.1atm, 1.12atm, 1.14atm, 1.16atm, 1.18atm, etc.), and the gas in the transfer container is consistent with the gas in the sealed instrument.

[0059] Specifically, the gas pressure in the transfer container is controlled to be 1-1.2 atm because within the gas pressure range of 1-1.2 atm, the distribution of gas molecules in the container is relatively uniform and stable, which helps to maintain the concentration and distribution of gas in the pores of the electrode sheet. Lower gas pressure (such as below 1 atm) may cause gas molecules in the pores to diffuse to the outside of the pores due to concentration gradient.

[0060] As an optional embodiment of the present invention, in step S2, the ion beam milling is performed in an ion beam milling instrument, and the technical parameters of the ion beam milling instrument include:

[0061] The ion gun is a saddle-type ion gun, and the number of ion guns is ≥ 3;

[0062] The ion gun voltage is 1-10 kV;

[0063] The ion gun current is 0.5-4.5mA;

[0064] The maximum ion beam cutting rate is ≥300μm / h.

[0065] Specifically, the protective atmosphere in the ion beam mill is consistent with the protective atmosphere in the sealed instrument and transfer container. The protective atmosphere in the ion beam mill mainly protects the sample from heat and sputtering damage generated by ion beam bombardment, and also helps to maintain the stability and efficiency of the milling process.

[0066] As an optional implementation of the present invention, in step S3, developer signal detection is performed on the cross section to be tested to obtain the pore distribution of the electrode sheet to be tested, specifically:

[0067] When developer signal detection is performed on at least one detection area of ​​a cross section to be tested, the pore distribution of the electrode sheet to be tested is directly obtained according to the detection condition of at least one detection area on the cross section to be tested;

[0068] Or, when developer signal detection is performed on multiple sections to be tested, the pore distribution of the electrode to be tested is obtained, specifically:

[0069] When developer signal detection is performed on at least one detection area of ​​each of the multiple sections to be measured, the pore distribution of the electrode piece to be measured is obtained by integrating the developer signal detection results of the detection areas of the multiple sections to be measured.

[0070] As an optional implementation manner of the present invention, the image analysis calculation includes:

[0071] The pore distribution image of the electrode sheet to be tested is imported into the image processing software. The software obtains the threshold value according to the obvious grayscale difference between the pores and the coating particles in the pore distribution image, and performs segmentation and marking according to the threshold value to obtain the particle area and the pore area;

[0072] The total number of pixels in the pore area is calculated by difference between the total number of pixels in the particle area and the total number of pixels in the pore distribution image, and the ratio of the total number of pixels in the pore area to the total number of pixels in the pore distribution image is the porosity of the electrode sheet to be tested.

[0073] As an optional embodiment of the present invention, the standard deviation of the electrode sheet porosity obtained by the above-mentioned electrode sheet porosity detection method is ≤0.41%, and the relative error of the electrode sheet porosity obtained by FIB-SEM three-dimensional reconstruction characterization is ≤3.73%.

[0074] The above-mentioned pore detection method of the electrode sheet is not limited to the pore detection of the electrode sheet, but can also be used for the pore detection of other porous structures. The electrode sheet can be a negative electrode sheet or a positive electrode sheet.

[0075] The present invention will be further described in detail below with reference to specific embodiments and comparative examples.

[0076] First of all, it should be noted that the electrode sheets to be tested in the embodiment, comparative example and the FIB-SEM three-dimensional reconstruction method are all prepared by the same method, and the specific method is as follows:

[0077] The electrode sheet to be tested is a negative electrode sheet, and its preparation method is as follows: graphite, SP, CMC and SBR are prepared in a mass ratio of 95.5:1.5:1.2:1.8 to prepare a slurry, the solvent is water, the slurry viscosity is adjusted to 4000±200mPa·s, and the prepared slurry is prepared at a double-sided surface density of 136g / m 2 They are evenly coated on 8μm copper foil, and the compaction density is 1.60g / cm 3 The negative electrode is rolled into a negative electrode sheet.

[0078] Example 1

[0079] S1: Place the electrode to be tested in the sample cell chamber of the true density meter, replace the gas in the chamber with argon gas, replace it 3 times to ensure the purity of the argon gas in the chamber and the gas pressure is 1.5atm, and maintain it at this pressure for 20s to allow the argon gas to be adsorbed or deposited in the pores of the electrode to be tested;

[0080] S2: Take out the electrode sheet to be tested obtained in step S1 from the true density meter and immediately put it into a pre-prepared transfer container, which is filled with argon gas and the pressure of argon gas is controlled to be 1.1atm. Then transfer the electrode sheet from the transfer container to an ion beam milling instrument for ion beam milling, wherein the ion gun is a saddle ion gun, the number of ion guns is 3; the ion gun voltage is 5kV; the ion gun current is 3.5mA; the maximum ion beam cutting rate is 400μm / h. After milling, a cross section to be tested is obtained;

[0081] S3: Using a SEM-EDS instrument, developer signal detection is performed on the detection area of ​​the cross section to be tested to obtain the pore distribution of the electrode to be tested; the pore distribution image of the electrode to be tested is imported into an image processing software, and the software obtains a threshold value according to the obvious grayscale difference between the pores and the coating particles in the pore distribution image, and performs segmentation and marking according to the threshold value to obtain a particle area and a pore area;

[0082] The total number of pixels in the pore area is calculated by difference between the total number of pixels in the particle area and the total number of pixels in the pore distribution image, and the ratio of the total number of pixels in the pore area to the total number of pixels in the pore distribution image is the porosity of the electrode sheet to be tested.

[0083] Example 2

[0084] S1: Place the electrode to be tested in the sample cell chamber of the true density meter, replace the gas in the chamber with neon gas, replace it 4 times to ensure the purity of the neon gas in the chamber and the gas pressure is 1.2atm, and maintain it at this pressure for 18s to allow the neon gas to be adsorbed or deposited in the pores of the electrode to be tested;

[0085] S2: Take out the electrode sheet to be tested obtained in step S1 from the autoclave and immediately put it into a pre-prepared transfer container, which is filled with neon gas and the pressure of neon gas is controlled to be 1.2atm. Then transfer the electrode sheet from the transfer container to an ion beam milling instrument for ion beam milling, wherein the ion gun is a saddle ion gun, the number of ion guns is 3; the ion gun voltage is 5kV; the ion gun current is 3.5mA; the maximum ion beam cutting rate is 400μm / h. After milling, a cross section to be tested is obtained;

[0086] S3: Using a SEM-EDS instrument, developer signal detection is performed on the detection area of ​​the cross section to be tested to obtain the pore distribution of the electrode to be tested; the pore distribution image of the electrode to be tested is imported into an image processing software, and the software obtains a threshold value according to the obvious grayscale difference between the pores and the coating particles in the pore distribution image, and performs segmentation and marking according to the threshold value to obtain a particle area and a pore area;

[0087] The total number of pixels in the pore area is calculated by difference between the total number of pixels in the particle area and the total number of pixels in the pore distribution image, and the ratio of the total number of pixels in the pore area to the total number of pixels in the pore distribution image is the porosity of the electrode sheet to be tested.

[0088] Example 3

[0089] S1: Place the electrode to be tested in the sample cell chamber of the true density meter, replace the gas in the chamber with helium, replace it 4 times to ensure the purity of the helium in the chamber and the pressure is 2.0atm, and keep it at this pressure for 22s to allow the helium to be adsorbed or deposited in the pores of the electrode to be tested;

[0090] S2: Take out the electrode sheet to be tested obtained in step S1 from the true density meter and immediately put it into a pre-prepared transfer container, which is filled with helium and the pressure of helium is controlled to be 1atm. Then transfer the electrode sheet from the transfer container to an ion beam milling instrument for ion beam milling, wherein the ion gun is a saddle ion gun, the number of ion guns is 3; the ion gun voltage is 5kV; the ion gun current is 3.5mA; the maximum ion beam cutting rate is 400μm / h. After milling, a cross section to be tested is obtained;

[0091] S3: Using a fluorescence spectrometer, developer signal detection is performed on the detection area of ​​the cross section to be tested to obtain the pore distribution of the electrode to be tested; the pore distribution image of the electrode to be tested is imported into the image processing software, the software obtains a threshold value according to the obvious grayscale difference between the pores and the coating particles in the pore distribution image, and segmentation and marking are performed according to the threshold value to obtain the particle area and the pore area;

[0092] The total number of pixels in the pore area is calculated by difference between the total number of pixels in the particle area and the total number of pixels in the pore distribution image, and the ratio of the total number of pixels in the pore area to the total number of pixels in the pore distribution image is the porosity of the electrode sheet to be tested.

[0093] Example 4

[0094] S1: Place the electrode to be tested in the sample cell chamber of the true density meter, replace the gas in the chamber with argon gas, replace it 3 times to ensure the purity of the argon gas in the chamber and the gas pressure is 1.5atm, and maintain this gas pressure for 20s to allow the argon gas to be adsorbed or deposited on the pore surface of the electrode to be tested;

[0095] S2: Take out the electrode sheet to be tested obtained in step S1 from the true density meter and immediately put it into a pre-prepared transfer container, which is filled with argon gas and the pressure of argon gas is controlled to be 1.1atm. Then transfer the electrode sheet from the transfer container to an ion beam milling instrument for ion beam milling, wherein the ion gun is a saddle ion gun, the number of ion guns is 3; the ion gun voltage is 5kV; the ion gun current is 3.5mA; the maximum ion beam cutting rate is 400μm / h. After milling, 4 cross sections to be tested are obtained;

[0096] S3: Using a SEM-EDS instrument, developer signal detection is performed on the detection areas of the four sections to be tested respectively, and the pore distribution conditions corresponding to the developer signal detection results of the four detection areas are obtained from the developer signal detection results of the four detection areas; the four pore distribution images are imported into an image processing software, and the software obtains a threshold value according to the obvious grayscale difference between the pores and the coating particles in the pore distribution image, and performs segmentation and marking according to the threshold value to obtain a particle area and a pore area;

[0097] The total number of pixels in the pore area is subtracted from the total number of pixels in the pore distribution image to obtain the total number of pixels in the pore area. The ratio of the total number of pixels in the pore area to the total number of pixels in the pore distribution image is the porosity of the electrode sheet to be tested. The final porosity data is the average porosity of the detection areas of the four sections to be tested.

[0098] Comparative Example 1

[0099] The main difference between this comparative example and Example 1 is that the gas pressure in the cavity after the gas is replaced in step S1 is 2.3 atm, and the other technical parameters and operation steps are the same as those in Example 1, specifically:

[0100] S1: Place the electrode to be tested in the sample cell chamber of the true density meter, and replace the gas in the chamber with argon gas for 3 times to ensure the purity of the argon gas in the chamber and the gas pressure is 2.3atm. Maintain this gas pressure for 20s to allow the argon gas to be adsorbed or deposited in the pores of the electrode to be tested.

[0101] Comparative Example 2

[0102] The main difference between this comparative example and Example 1 is that the gas pressure in the chamber after the gas is replaced in step S1 is 1 atm, and the other technical parameters and operation steps are the same as those in Example 1, specifically:

[0103] S1: Place the electrode to be tested in the sample cell chamber of the true density meter, and replace the gas in the chamber with argon gas for 3 times to ensure the purity of the argon gas in the chamber and the gas pressure is 1atm. Maintain this gas pressure for 20s to allow the argon gas to be adsorbed or deposited in the pores of the electrode to be tested.

[0104] Comparative Example 3

[0105] The main difference between this comparative example and Example 1 is that the gas pressure in the transfer container in step S2 is 0.9 atm, and the other technical parameters and operating steps are the same as those in Example 1.

[0106] Comparative Example 4

[0107] The porosity of the electrode sheet is determined by the FIB-SEM three-dimensional reconstruction method, which specifically includes the following steps:

[0108] (1) Sample preparation

[0109] An electrode sheet to be tested prepared by the same method as in the embodiment or comparative example is selected, and the electrode sheet to be tested is fixed on a sample stage to ensure that it will not move or deform during processing and imaging.

[0110] A layer of conductive material (such as Pt or C) is plated on the surface of the electrode to be tested to increase the conductivity of the electrode to be tested and to protect the surface of the electrode to be tested from damage by the ion beam.

[0111] (2) Positioning and marking

[0112] SEM observation: Use SEM to observe the electrode to be tested, locate and mark the area to be tested;

[0113] (3) Sectioning and imaging

[0114] Preliminary cutting: Using the precise control capability of FIB, preliminary cutting is performed in the area to be tested to form a groove of a certain width;

[0115] Serial sectioning: The continuous sectioning function of FIB is used to perform serial sectioning inside the groove. After each sectioning, the surface of the section is imaged using SEM to record the sectioning information.

[0116] Iterative operation: Repeat the slicing and imaging steps until the 3D data collection of the entire groove is completed.

[0117] (4) 3D reconstruction

[0118] Image collection: Collect all SEM images after slicing to form a series of slice image data sets.

[0119] Image preprocessing: Preprocess the slice images, including filtering, noise reduction, alignment and other operations, to improve image quality and reconstruction accuracy.

[0120] 3D reconstruction: Use professional 3D reconstruction software (such as Avizo, etc.) to perform 3D reconstruction on the pre-processed slice images. Use algorithms to stack and fuse 2D slice images into a 3D structure model.

[0121] Post-processing: Post-processing is performed on the reconstructed 3D model, including smoothing the surface, filling holes, optimizing the structure, etc., to obtain more accurate 3D structure information.

[0122] (5) Results analysis

[0123] Structural analysis: Detailed analysis of the reconstructed three-dimensional structure, including size measurement, shape analysis, porosity calculation, etc.

[0124] The FIB-SEM three-dimensional reconstruction characterization (Comparative Example 4), the detection methods provided in Examples 1-4 and Comparative Examples 1-3 were respectively tested 5 times, the porosity calculated each time was recorded, and the average value was calculated. The relative error of the average value of each example relative to the average value of the FIB-SEM three-dimensional reconstruction method was calculated to determine the accuracy of the method of the present invention. The precision of the method of the present invention, that is, the stability of the results, was judged based on the standard deviation of the five repeated test results in each example or comparative example. The specific data are shown in Table 1:

[0125] Table 1

[0126]

[0127] According to Table 1, in Comparative Example 1, since the gas pressure in the cavity after the gas is replaced in step S1 is too high, the distribution of gas in the pores becomes uneven, forming a local high-pressure area, resulting in large differences in the results of the five tests and poor repeatability. The measured porosity is significantly different from the average value of the standard method (FIB-SEM three-dimensional reconstruction) and has low accuracy.

[0128] According to Table 1, in Comparative Example 2, the gas pressure in the cavity after the gas is replaced in step S1 is too low, resulting in insufficient gas concentration in the pores. In addition, dissipation occurs during the transfer process, resulting in large differences in the results of the five tests, poor repeatability, and a large difference between the measured porosity and the average value of the standard method, with low accuracy.

[0129] According to Table 1, in Comparative Example 3, since the gas pressure in the transfer container in step S2 is too low, the gas in the pores may dissipate, and the measured porosity is significantly different from the average value of the standard method, and the accuracy is low.

[0130] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting pores of an electrode sheet, characterized in that: The steps include: S1: placing the electrode sheet to be tested in a sealed instrument, replacing the gas in the sealed instrument with a gaseous developer, so as to adsorb or deposit the gaseous developer in the pores on the surface of the electrode sheet to be tested; S2: transferring the electrode sheet to be tested obtained in step S1 to a transfer container, and then performing ion beam milling to obtain one or more cross sections to be tested; S3: performing developer signal detection on the cross section to be tested to obtain the pore distribution of the electrode sheet to be tested, and calculating the electrode sheet porosity through image analysis.

2. The pore detection method of the electrode sheet according to claim 1, characterized in that: The gaseous developer includes an inert gas for gaseous developer signal detection using SEM-EDS or a fluorescent gas for gaseous developer signal detection using a spectrum analyzer.

3. The pore detection method of the electrode sheet according to claim 2, characterized in that: The inert gas includes one or more of argon, neon, helium, xenon, and krypton; And / or, the spectral analysis instrument includes one of a fluorescence spectrometer, a Raman spectrometer, and an infrared spectrometer; And / or, the fluorescent gas includes one or more of argon, neon, helium, xenon, krypton, benzene derivatives, and naphthalene derivatives.

4. The pore detection method of the electrode sheet according to claim 1, characterized in that: In step S1, the sealed instrument is a true density meter or a high-pressure reactor; the number of times the gas in the sealed instrument is replaced is ≥2 times.

5. The method for detecting pores of an electrode sheet according to claim 1, characterized in that: In step S1, after the gas in the sealed instrument is replaced with a gaseous developer, the pressure of the inert gas or fluorescent gas in the sealed instrument cavity is maintained at 1.2-2.0 atm for a maintenance time of ≥15 s.

6. The method for detecting pores of an electrode sheet according to claim 1, characterized in that: In step S2, the transfer is to take the electrode sheet out of the sealed instrument and immediately put it into a transfer container with an air pressure of 1-1.2 atm; And / or, the gas in the transfer container is consistent with the gas in the sealed instrument.

7. The method for detecting pores of an electrode sheet according to claim 1, characterized in that: In step S2, the ion beam milling is performed in an ion beam milling instrument, and the technical parameters of the ion beam milling instrument include: The ion gun is a saddle-type ion gun, and the number of ion guns is ≥ 3; The ion gun voltage is 1-10 kV; The ion gun current is 0.5-4.5mA; The maximum ion beam cutting rate is ≥300μm / h.

8. The method for detecting pores of an electrode sheet according to claim 1, characterized in that: In step S3, developer signal detection is performed on the cross section to obtain the pore distribution of the electrode sheet to be tested, specifically: When developer signal detection is performed on a detection area of ​​a section to be tested, the pore distribution of the electrode sheet to be tested is directly obtained according to the detection condition of at least one detection area on the section to be tested; Or, when developer signal detection is performed on multiple sections to be tested, the pore distribution of the electrode to be tested is obtained, specifically: When developer signal detection is performed on at least one detection area of ​​each of the multiple sections to be measured, the pore distribution of the electrode piece to be measured is obtained by integrating the developer signal detection results of the detection areas of the multiple sections to be measured.

9. The method for detecting pores of an electrode sheet according to claim 1, characterized in that: The image analysis calculation includes: The pore distribution image of the electrode sheet to be tested is imported into the image processing software. The software obtains the threshold value according to the obvious grayscale difference between the pores and the coating particles in the pore distribution image, and performs segmentation and marking according to the threshold value to obtain the particle area and the pore area; The total number of pixels in the pore area is calculated by difference between the total number of pixels in the particle area and the total number of pixels in the pore distribution image, and the ratio of the total number of pixels in the pore area to the total number of pixels in the pore distribution image is the porosity of the electrode sheet to be tested.

10. The method for detecting pores of an electrode sheet according to claim 1, characterized in that: The standard deviation of the porosity of the electrode sheet is ≤0.41%, and the relative error of the porosity of the electrode sheet obtained by FIB-SEM three-dimensional reconstruction is ≤3.73%.

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