Method for detecting insoluble particles in electrode auxiliary material of secondary battery

Abstract

The invention provides a method for detecting insoluble particles in an electrode auxiliary material of a secondary battery, the auxiliary material is a binder or a thickener, and the method comprises the following steps: (S1) dissolving the auxiliary material containing the insoluble particles in a solvent to obtain a solution containing the insoluble particles; (S2) coating the solution containing the insoluble particles obtained in the step (S1) on a transparent plate to obtain a coated transparent plate; (S3) shooting the coated transparent plate obtained in the step (S2) through an optical microscope to obtain an image; and (S4) the image obtained in the step (S3) is processed through an image processing device, the image processing device comprises an input module, a judgment module, a data analysis module and an output module, and the image processing device recognizes insoluble particles through an image recognition algorithm. Therefore, detection can be completed quickly and accurately, and subjective errors of manual judgment and counting are eliminated.

Description

Technical Field

[0001] The present application relates to the technical field of secondary batteries, and in particular to a method for detecting insoluble particles of electrode auxiliary materials of secondary batteries. Background Art

[0002] When the electrode auxiliary materials used in the production of secondary batteries, especially auxiliary materials with high viscosity (such as binders and thickeners), are dissolved in a solvent to form a slurry, insoluble substances often appear in the slurry. These insoluble substances are not conducive to slurry filtration. The appearance of insoluble substances increases filtration costs and negatively affects production efficiency. In addition, when the above slurry is applied to battery pole pieces, it can also cause surface defects of the pole pieces and increase or decrease in battery resistance, which has an undesirable impact on the appearance of the pole pieces and the performance of the battery.

[0003] At present, the main methods for controlling insoluble matter in slurry are volumetric analysis, spectrophotometry and visual method. Among them, the volumetric analysis method has a large error when facing high-viscosity samples, the spectrophotometry method is greatly affected by the operating conditions, and the test results fluctuate too much. The visual counting method relies on the subjective judgment of the tester. When the insoluble matter is small in size and large in number, it is impossible to accurately count, and it is especially easy to ignore transparent insoluble matter.

[0004] Therefore, there is a need in the art for a method that can accurately detect insoluble particles in electrode auxiliary materials of secondary batteries. Summary of the invention

[0005] In order to solve the above problems, the purpose of the present application is a method for detecting insoluble particles in an electrode auxiliary material of a secondary battery, the method comprising the following steps: (S1) dissolving an electrode auxiliary material containing insoluble particles in a solvent to obtain a solution containing insoluble particles; (S2) coating the solution containing insoluble particles obtained in step (S1) on a transparent plate to obtain a coated transparent plate; (S3) photographing the coated transparent plate obtained in step (S2) through an optical microscope to obtain an image; (S4) processing the image obtained in step (S3) through an image processing device, wherein the image processing device comprises an input module, a judgment module, a data analysis module and an output module, wherein the image processing device identifies insoluble particles through an image recognition algorithm. By means of the method according to the present application, when detecting insoluble particles in an electrode auxiliary material, the detection can be completed quickly, accurately and in simple steps, without the need to visually observe the solution of the electrode auxiliary material for a long time to determine whether there are foreign objects therein, thereby eliminating subjective errors in human judgment and counting.

[0006] According to one embodiment of the method of the present application, the concentration of the electrode auxiliary material in the solution containing insoluble particles is 0.25 wt % to 2 wt %. According to one embodiment of the method of the present application, the solution containing insoluble particles has a viscosity of 1000 mPaS to 7000 mPaS. When the solution has a viscosity defined in the present application, the best detection effect can be obtained. For example, when the viscosity is too high, the liquid film may be uneven after coating, and the solution leveling may be poor, which may affect the detection result. When the viscosity is too low, the observed solution has a low content of insoluble particles due to excessive dilution, which is not conducive to statistical accuracy. In addition, the viscosity described in the present application is similar to the industrial use conditions of the electrode auxiliary material. It is more practical to detect and count the information of insoluble particles at this viscosity.

[0007] According to one embodiment of the method of the present application, the insoluble particles are in the form of particles, which may be spherical, ellipsoidal, hemispherical, cylindrical or conical.

[0008] According to one embodiment of the method of the present application, the auxiliary material is a binder or a thickener, and the solvent is water or an organic solvent. In one embodiment, when the electrode auxiliary material is a water-soluble electrode auxiliary material, the solvent is water, and the insoluble particles are particles that are insoluble in water. In another embodiment, when the electrode auxiliary material is insoluble in water, the solvent is an organic solvent, such as an alcohol, an ester, an ether, preferably N-methylpyrrolidone, and the insoluble particles are particles that are insoluble in the organic solvent.

[0009] According to one embodiment of the method of the present application, the insoluble particles include transparent insoluble particles, and the optical microscope is a polarizing microscope. Since transparent insoluble particles are not obvious under an ordinary optical microscope, the present application can capture the transparent insoluble particles in the acquired image by using a polarizing microscope, thereby improving the accuracy of the detection result.

[0010] According to one embodiment of the method of the present application, in step (S1), the electrode auxiliary material is dissolved in a solvent, and in particular, a suitable solvent is selected according to the electrode auxiliary material so that the main components of the electrode auxiliary material can be dissolved in the solvent. According to one embodiment of the method of the present application, the electrode auxiliary material containing insoluble particles includes at least one of polyamide, styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene, and when the electrode auxiliary material is styrene-butadiene rubber or carboxymethyl cellulose, the solvent is water, and when the electrode auxiliary material containing insoluble particles is polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene, the solvent is N-methylpyrrolidone.

[0011] According to one embodiment of the method of the present application, in step (S2), the solution containing insoluble particles obtained in (S1) is coated on a transparent plate by an automatic coating device, thereby avoiding errors that may be introduced in manual coating, thereby improving the accuracy and repeatability of the test results.

[0012] According to one embodiment of the method of the present application, in step (S2), a rectangular frame of a specific size is carved on a transparent plate, a coating rod is aligned with the rectangular frame area, 5 ml of the solution to be tested is drawn and evenly coated on the outer side of the rectangular frame close to the coating rod, and an automatic coating device is used to coat the auxiliary material solution on the transparent plate. This step needs to ensure that the liquid film completely covers the rectangular frame. In some embodiments, the transparent plate is made of at least one of polyethylene terephthalate, polymethyl methacrylate, polystyrene, and polyvinyl chloride. In some embodiments, the carved rectangular frame has a side length of 2.5 cm-10 cm and an area of ​​25 cm 2 -100cm 2 coating rod thickness of 50μm-500μm, preferably about 200μm, wherein the coating speed of the automatic coating equipment is set to 0.005m / s-0.05m / s.

[0013] According to one embodiment of the method of the present application, in step (S3), the coated transparent plate is placed under the stage of an optical microscope with a polarized lens, and the mode of automatic shooting and stitching of photos is used, the shooting area is set to completely include the rectangular frame, and automatic shooting and stitching are started, and the photos taken are saved. In some embodiments, the light source of the polarized microscope in step (S3) is coaxial light, the brightness is 750lux-1500lux, and the magnification is 20 times to 50 times; in order to avoid the volatilization of solvents affecting the observation results, the time from coating to completion of shooting needs to be controlled within 10 minutes, preferably within 5 minutes.

[0014] According to one embodiment of the method of the present application, step (S3) and step (S3) are repeated multiple times, for example, 3 to 10 times, preferably 9 to 10 times. Thus, even when there are only a very small amount of insoluble particles in the electrode auxiliary material, a detection result with a very small error can be obtained by the method of the present application.

[0015] According to one embodiment of the method of the present application, in step (S4), the photo taken in step (S3) is imported into the image processing device through an input module.

[0016] According to one embodiment of the method of the present application, the judgment module identifies the suspicious area through a target detection algorithm, and judges whether there are insoluble particles in the suspicious area through a neural network classifier.

[0017] According to one embodiment of the method of the present application, the judgment module can distinguish insoluble particles, bubbles, scratches on the transparent plate, and dust introduced during the detection process. Therefore, the method of the present application can avoid the influence of interference factors such as bubbles and scratches generated in the detection step on the detection results.

[0018] According to one embodiment of the method of the present application, the analysis module obtains the contour of the insoluble particles through an edge detection algorithm, and calculates the particle size, number and distribution of the insoluble particles.

[0019] According to one embodiment of the method of the present application, the output module can output the number and particle size distribution of insoluble particles.

[0020] According to one embodiment of the method of the present application, the particle size of the insoluble particles is greater than 5 micrometers. With the help of a polarizing microscope, the insoluble particles with a particle size greater than 5 micrometers can be captured in an image and then identified by an image processing device.

[0021] According to one embodiment of the method of the present application, the electrode auxiliary material containing insoluble particles is used to prepare a secondary battery, especially for preparing an active material layer on an electrode plate of a secondary battery, and the particle size of the insoluble particles is above 50 microns. The inventors of the present application found that when insoluble particles with a particle size of 50 microns or more are used in electrochemical devices, such as in positive or negative electrode plates, especially in positive active material layers or negative active material layers, such insoluble particles will have a significant negative impact on the performance of the battery. Therefore, when the electrode auxiliary material containing insoluble particles is used to prepare a secondary battery, only counting insoluble particles with a particle size of 50 microns or more can obtain higher statistical efficiency and more accurate particle counts. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the above-mentioned purposes, features and advantages of the present application easier to understand, the specific implementation methods of the present application are described in detail below in conjunction with the accompanying drawings. In the following description, many specific details are set forth to fully understand the present application, but the present application can also be implemented in other ways different from those described herein, so the present application is not limited to the specific embodiments disclosed below.

[0024] Figure 1A Schematically showing an image of a transparent plate observed by visual inspection;

[0025] Figure 1B Schematically shows an image of a transparent plate observed through an ordinary optical microscope;

[0026] Figure 1C Schematic diagram showing an image of a transparent plate observed through a polarizing microscope;

[0027] Figure 2AThe detection results of Example 1 are schematically shown;

[0028] Figure 2B The detection results of Example 2 are schematically shown. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be clearly and completely described in conjunction with the embodiments below. Obviously, the described embodiments are part of the embodiments of the present application, rather than all of the embodiments. The relevant embodiments described herein are illustrative in nature and are used to provide a basic understanding of the present application. The embodiments of the present application should not be interpreted as limiting the present application. Based on the technical scheme provided by the present application and the embodiments given, all other embodiments obtained by those skilled in the art without making creative work are within the scope of protection of the present application.

[0030] For simplicity, only some numerical ranges are specifically disclosed herein. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, and any upper limit can be combined with any other upper limit to form an unspecified range. In addition, each separately disclosed point or single value can itself be combined as a lower limit or upper limit with any other point or single value or with other lower limits or upper limits to form an unspecified range.

[0031] In the description herein, unless otherwise specified, “above” and “below” include the number.

[0032] Unless otherwise specified, the terms used in this application have the commonly known meanings generally understood by those skilled in the art. Unless otherwise specified, the numerical values ​​of the various parameters mentioned in this application can be measured using various measurement methods commonly used in the art (for example, they can be tested according to the methods given in the examples of this application).

[0033] A list of items connected by the terms "at least one of," "at least one of," "at least one of," or other similar terms may mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A may contain a single component or multiple components. Item B may contain a single component or multiple components. Item C may contain a single component or multiple components.

[0034] In the context of the present application, "insoluble particles" and "insoluble matter" are relative rather than absolute concepts. For example, when the solvent is water, insoluble particles should be understood as particles that are insoluble in water, and when the solvent is a specific organic solvent, insoluble particles should be understood as particles that are insoluble in the organic solvent.

[0035] It will be appreciated that, unless otherwise stated, features of any specific embodiment discussed herein may be combined with one or more features of any one or more embodiments otherwise discussed or considered herein.

[0036] In the context of this application, an "electrochemical device" comprises a negative electrode, a positive electrode, an electrolyte and a separator.

[0037] In some embodiments, the electrochemical device of the present application includes, but is not limited to: all kinds of primary batteries, secondary batteries, fuel cells, solar cells or capacitors.

[0038] In some embodiments, the electrochemical device is a sodium ion battery.

[0039] In some embodiments, the electrochemical device is a lithium secondary battery.

[0040] In some embodiments, the lithium secondary battery includes, but is not limited to, a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

[0041] Example 1

[0042] The insoluble particles in the electrode excipients are detected by the following steps:

[0043] (i) 10 g of CMC (carboxymethyl cellulose) sample CMC2200A purchased from Daicel Japan was dissolved in 990 g of deionized water, stirred at 2000 r / min, dispersed for 2 h, and allowed to stand for 4 h to defoam, to obtain a 1 wt % CMC2200A sample solution;

[0044] (ii) Take a polyethylene terephthalate transparent plate with a length of 12 cm and a width of 15 cm, use a utility knife to carve out a square with a side length of 5 cm, use a coating rod with a thickness of 200 μm, draw 3 mL of CMC2200A sample solution and drip it evenly between the coating rod and the rectangular frame; turn on the automatic coating equipment and set the coating speed to 0.01 m / s;

[0045] (iii) placing the coated transparent plate under the stage of an optical microscope equipped with a polarizing lens, using an automatic shooting mode, setting the shooting area to completely include the rectangular frame, starting automatic shooting, and saving the photographed photos;

[0046] Repeat steps (ii) and (iii) 9 times in total;

[0047] (iv) The nine photographs are imported into an image processing device, and the number and particle size distribution data of the insoluble particles are obtained after being processed by the image processing device.

[0048] Figure 1B The image of insoluble particles on a transparent plate observed by a common optical microscope is schematically shown, and Figure 1C The image of the same insoluble particles on a transparent plate observed through a polarizing microscope is schematically shown. It can be seen that the insoluble particles in the solution can be more clearly identified under the polarizing microscope.

[0049] Figure 2A The number and particle size distribution of the insoluble particles obtained in Example 1 are shown in FIG.

[0050] Example 2

[0051] The insoluble particles in the CMC sample CMC2200B commercially available from Daicel of Japan were detected by the same procedure as in Example 1.

[0052] The number and size distribution of insoluble particles are shown in Figure 2B middle.

[0053] Comparative Example 1

[0054] The insoluble particles in the electrode excipients are detected by the following steps:

[0055] (i) 10 g of CMC sample CMC2200A purchased from Daicel Japan was dissolved in 990 g of deionized water, stirred at 2000 r / min, dispersed for 2 h, and allowed to stand for 4 h to defoam, to obtain a 1 wt % CMC2200A sample solution;

[0056] (ii) Take a polyethylene terephthalate transparent plate with a length of 12 cm and a width of 15 cm, use a utility knife to carve out a square with a side length of 5 cm, use a coating rod with a thickness of 200 μm, take 3 mL of 1 wt% CMC2200A sample solution and drip it evenly between the coating rod and the rectangular frame; manually push the coating rod at a uniform speed and slowly to complete the coating;

[0057] (iii) Under the illumination of a set of light poles, the number of insoluble particles in the rectangular frame of the transparent plate is manually counted.

[0058] Repeat steps (ii) and (iii) for a total of 9 times, and take the sum of the 9 counts as the final detection result.

[0059] Figure 1A An image of a transparent plate observed visually is schematically shown.

[0060] Comparative Example 2

[0061] The insoluble particles in CMC (carboxymethyl cellulose) electrode auxiliary material CMC2200B commercially available from Daicel Japan were detected by the same steps as in Comparative Example 1.

[0062] The test results of Examples 1-2 and Comparative Examples 1-2 are shown in Table 1.

[0063] Table 1

[0064]

[0065]

[0066] The number of insoluble particles calculated in Example 2 is 2.2 times that of Example 1, while the number of insoluble particles calculated in Comparative Example 2 is only 1.4 times that of Comparative Example 1. It can be seen that when there are more insoluble particles in the electrode auxiliary material, the method of the present application can especially achieve better detection results, which can be attributed to the fact that when the number of insoluble particles in the electrode auxiliary material is large and the particle size is small, the error of the visual method is further increased.

[0067] Example 3

[0068] The insoluble particles in the CMC sample QN4115 purchased from Beijing Biolab Technology Co., Ltd. were detected by the following steps:

[0069] (i) Dissolve 7.5 g of QN4115 in 992.5 g of deionized water at a stirring speed of 2000 r / min for 3 h and stand for 4 h to defoam to obtain a 0.75 wt% QN4115 sample solution;

[0070] (ii) Take a polyethylene terephthalate transparent plate with a length of 12 cm and a width of 15 cm, use a utility knife to carve out a square with a side length of 5 cm, use a coating rod with a thickness of 200 μm, draw 3 mL of QN4115 sample solution and drip it evenly between the coating rod and the rectangular frame; turn on the automatic coating equipment and set the coating speed to 0.01 m / s;

[0071] (iii) placing the coated transparent plate under the stage of an optical microscope equipped with a polarizing lens, using an automatic shooting mode, setting the shooting area to completely include the rectangular frame, starting automatic shooting, and saving the photographed photos;

[0072] Repeat steps (ii) and (iii) 9 times;

[0073] (iv) The nine photographs are imported into an image processing device, and the number and particle size distribution data of the insoluble particles are obtained after being processed by the image processing device.

[0074] Example 3 was repeated 9 times, and the results were recorded as QN4115-1 to QN4115-9.

[0075] Comparative Example 3

[0076] The insoluble particles in the CMC sample QN4115 purchased from Beijing Biolab Technology Co., Ltd. were detected by the following steps:

[0077] (i) 7.5 g of CMC sample QN4115 was dissolved in 992.5 g of deionized water, with a stirring speed of 2000 r / min, a dispersion time of 3 h, and allowed to stand for 4 h to defoam, to obtain a 0.75 wt% QN4115 sample solution;

[0078] (ii) Take a polyethylene terephthalate transparent plate with a length of 12 cm and a width of 15 cm, use a utility knife to carve out a square with a side length of 5 cm, use a coating rod with a thickness of 200 μm, draw 3 mL of QN4115 sample solution and drip it evenly between the coating rod and the rectangular frame; manually push the coating rod at a uniform and slow speed to complete the coating;

[0079] (iii) manually counting the number of insoluble particles in the rectangular frame of a transparent plate under the illumination of a set of light poles;

[0080] Repeat steps (ii) and (iii) for a total of 9 times, and take the sum of the 9 counts as the final detection result.

[0081] Comparative Example 3 was repeated 9 times, and the results obtained were recorded as QN4115-1 to QN4115-9.

[0082] The test results of Example 3 and Comparative Example 3 are shown in Table 2.

[0083] Table 2

[0084] Example 3 Comparative Example 3 QN4115-1 540 225 QN4115-2 557 260 QN4115-3 584 170 QN4115-4 512 154 QN4115-5 553 190 QN4115-6 598 227 QN4115-7 572 178 QN4115-8 517 164 QN4115-9 532 271 COV 5.33％ 20.1％

[0085] Example 4

[0086] (i) 1 g of CMC without insoluble particles was fully dissolved in 100 ml of deionized water, 10 mg of graphite was added, the mixture was stirred at 2000 r / min, dispersed for 2 h, and allowed to stand for 4 h to defoam, to obtain a dispersion containing 10 mg of insoluble particles (graphite);

[0087] (ii) Take a polyethylene terephthalate transparent plate with a length of 12 cm and a width of 15 cm, use a utility knife to carve out a square with a side length of 5 cm, use a coating rod with a thickness of 200 μm, absorb 1 mL of graphite dispersion and evenly drip it between the coating rod and the rectangular frame; turn on the automatic coating equipment and set the coating speed to 0.01 m / s;

[0088] (iii) placing the coated transparent plate under the stage of an optical microscope equipped with a polarizing lens, using an automatic shooting mode, setting the shooting area to completely include the rectangular frame, starting automatic shooting, and saving the photographed photos;

[0089] Repeat steps (ii) and (iii) 9 times in total;

[0090] (iv) The nine photographs are introduced into an image processing device, and the number of insoluble particles with a particle size of ≥50 μm is obtained after being processed by the image processing device.

[0091] Comparative Example 4

[0092] (i) 1 g of CMC without insoluble particles was fully dissolved in 100 ml of deionized water, 10 mg of graphite was added, the mixture was stirred at 2000 r / min, dispersed for 2 h, and allowed to stand for 4 h to defoam, to obtain a dispersion containing 10 mg of insoluble particles (graphite);

[0093] (ii) Take a polyethylene terephthalate transparent plate with a length of 12 cm and a width of 15 cm, use a utility knife to carve out a square with a side length of 5 cm, use a coating rod with a thickness of 200 μm, draw 1 mL of the test solution and drip it evenly between the coating rod and the rectangular frame; manually push the coating rod at a uniform and slow speed to complete the coating;

[0094] (iii) manually counting the number of insoluble particles in the rectangular frame of a transparent plate under the illumination of a set of light poles;

[0095] Repeat steps (ii) and (iii) for a total of 9 times, and take the sum of the 9 counts as the final detection result.

[0096] Light obscuration particle size analyzer measurement

[0097] Fully dissolve 1g of CMC without insoluble particles in 100ml of deionized water, add 10mg of graphite, stir at 2000r / min, disperse for 2h, let stand for 4h to defoam, and obtain a dispersion containing 10mg of insoluble particles (graphite). Take 1ml of the dispersion and dilute it, and use a light obscuration particle size analyzer (AccuSizer A7000 AD particle size analyzer) to count the number of insoluble particles with a particle size ≥50μm.

[0098] Repeat the above process 9 times, and take the sum of the 9 counts as the final statistical result.

[0099] The number of insoluble particles obtained by Example 4, Comparative Example 4 and the light obstruction particle size analyzer measurement is shown in Table 3.

[0100] Table 3

[0101]

[0102] It can be seen that the detection method according to the present application can quantitatively characterize the content and size distribution of insoluble particles in electrode excipients, and the discrimination and repeatability of the detection method according to the present application are significantly better than the existing visual counting method.

[0103] It should be understood by those skilled in the art that the above modules or steps of the present application can be implemented by a general-purpose computing device, they can be concentrated on a single computing device, or distributed on a network composed of multiple computing devices, optionally, they can be implemented by a program code executable by a computer device, so that they can be stored in a storage device and executed by the computing device, or they can be made into individual integrated circuit modules, or multiple modules or steps therein can be made into a single integrated circuit module for implementation. Thus, the present application is not limited to any specific combination of hardware and software.

[0104] Although some exemplary embodiments of the present application have been illustrated and described, the present application is not limited to the disclosed embodiments. On the contrary, those skilled in the art will recognize that some modifications and changes may be made to the described embodiments without departing from the spirit and scope of the present application as described in the appended claims, and these modifications and changes also fall within the scope of protection of the present application.

Claims

1. A method for detecting insoluble particles in an electrode auxiliary material of a secondary battery, wherein the auxiliary material is a binder or a thickener, characterized in that: The method comprises the following steps: (S1) dissolving the electrode auxiliary material containing insoluble particles in a solvent to obtain a solution containing insoluble particles; (S2) coating the solution containing the insoluble particles obtained in step (S1) on a transparent plate to obtain a coated transparent plate; (S3) photographing the coated transparent plate obtained in step (S2) through an optical microscope to obtain an image; (S4) Processing the image obtained in step (S3) by an image processing device, wherein the image processing device includes an input module, a judgment module, a data analysis module and an output module, and the image processing device identifies insoluble particles by an image recognition algorithm.

2. The method according to claim 1, characterized in that The solution containing the insoluble particles has a viscosity of 1000 mPaS to 7000 mPaS.

3. The method according to claim 1, characterized in that The solvent is water or an organic solvent.

4. The method according to claim 1, characterized in that: The insoluble particles include transparent insoluble particles, and the optical microscope is a polarizing microscope.

5. The method according to claim 1, characterized in that The judgment module identifies the suspicious area through a target detection algorithm, and judges whether there are insoluble particles in the suspicious area through a neural network classifier.

6. The method according to claim 1, characterized in that The judgment module can distinguish insoluble particles, bubbles, scratches on the transparent plate, and dust introduced during the detection process.

7. The method according to claim 1, characterized in that The analysis module obtains the contour of the insoluble particles through an edge detection algorithm, and calculates the particle size, quantity and distribution of the insoluble particles.

8. The method according to claim 1, characterized in that The particle size of the insoluble particles is above 5 microns.

9. The method according to claim 1, characterized in that: The output module can output the number and particle size distribution of insoluble particles.

10. The method according to claim 1, characterized in that The particle size of the insoluble particles is above 50 microns.

11. The method according to claim 10, characterized in that The auxiliary material includes at least one of polyamide, styrene-butadiene rubber, carboxymethyl cellulose, polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene, and when the auxiliary material is styrene-butadiene rubber or carboxymethyl cellulose, the solvent is water, and when the auxiliary material is polyamide, polyvinylidene fluoride or polyvinylidene fluoride-hexafluoropropylene, the solvent is N-methylpyrrolidone.

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