Slurry dispersing performance evaluation method

Abstract

The invention relates to a slurry dispersing performance evaluation method which comprises the following steps: in a negative pressure environment, continuously conveying slurry to a sieving system for sieving, the sieving system comprising a predetermined number of sieves which are sequentially arranged from top to bottom; timing is started after the slurry is stably sieved, and when the stably sieved slurry reaches a preset amount, conveying of the slurry is stopped, and the time required for obtaining the preset amount of the stably sieved slurry is recorded; counting the number of residual particles on each screen; and evaluating the dispersing performance of the slurry according to the time and the number of particles remained on each screen. The positive and negative electrode slurry produced in the slurry mixing process in the lithium battery manufacturing process is detected and evaluated through a multi-mesh screen negative pressure screening method, multi-angle evaluation of the dispersion performance of the slurry is achieved, and the authenticity and accuracy of the dispersion performance of the slurry are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium battery slurry production, and particularly to a method for evaluating the dispersion performance of slurry. Background Art

[0002] Lithium battery slurry plays a key role in the production process, directly affecting the performance and stability of lithium batteries. Lithium battery slurry needs to have good fluidity, stability, and uniformity to provide stable and reliable raw materials for subsequent coating processes, ensuring the consistency and reliability of the batteries. However, after the slurry is prepared, sedimentation may occur due to various reasons, which has a great impact on subsequent processes such as coating, possibly leading to defects in the macroscopic appearance of the electrode sheet and inconsistencies in the microscopic composition of the electrode sheet, thereby affecting the electrical performance of the battery, such as voltage drop and reduced cycle life. Therefore, it is essential to evaluate the dispersion performance of the positive and negative electrode slurries before coating for the manufacture of lithium batteries.

[0003] Currently, in the manufacturing process of lithium-ion batteries, there are mainly three directions for evaluating the dispersion performance of lithium-ion battery slurry: viscosity, solid content, and particles. These three factors interact with each other and jointly characterize the dispersion performance of the slurry. Among them, the size and quantity of the particles contained in the slurry will greatly affect subsequent processes. For example, too large particles will cause sedimentation during slurry storage, transportation, or filtration, increasing the viscosity of the slurry, deteriorating the uniformity, and ultimately blocking the pipeline; larger particles will block at the lip of the coating die head, forming vertical stripes on the coated film surface and reducing the surface density at that place, affecting the performance and interface of the finished battery; while smaller particles will be coated on the film surface, affecting subsequent processes such as rolling and cutting and stacking. However, in the current scenario of lithium battery manufacturing, for the particle index, only a scraping fineness gauge can be used to measure the maximum particles in the slurry, and it is impossible to comprehensively and effectively evaluate the particles in the slurry. Moreover, the readings of the scraping fineness gauge have a certain degree of subjective judgment, and differences in readings will occur due to changes in the testing personnel and differences in personnel capabilities. Summary of the Invention

[0004] Based on this, the purpose of the present invention is to provide a method for evaluating the dispersion performance of slurry, which can quickly, effectively, and conveniently judge the size and quantity of the particles contained in the slurry.

[0005] To achieve the above purpose, the present invention adopts the following technical solutions: The present invention first provides a method for evaluating the dispersion performance of slurry, which includes the following steps: S1. Under a negative pressure environment, continuously transport the slurry to a sieving system for sieving. The sieving system includes a predetermined number of sieves arranged in sequence from top to bottom; S2. Start timing after the slurry has passed through the sieve stably. When the stably sieved slurry reaches a predetermined amount, stop transporting the slurry and record the time required to obtain the predetermined amount of stably sieved slurry. S3. Count the number of particles remaining on each of the sieves. S4. Evaluate the dispersion performance of the slurry based on the time duration and the number of particles remaining on each of the sieves.

[0006] As a further improvement to the above solution of the present invention, in the sieving system, the number of the sieves is n, where n is a positive integer and 3 ≤ n ≤ 5. From top to bottom, the mesh numbers of the n sieves are M1, M2, …, M n And M1, M2, …, M n Increase in sequence.

[0007] As a further improvement to the above solution of the present invention, the mesh number of the sieve is 60 - 150 meshes; and / or, the vertical distance between any two adjacent sieves is 3 - 5 cm.

[0008] As a further improvement to the above solution of the present invention, in step S2, the pressure P of the negative pressure environment satisfies: -15 kPa ≤ P ≤ -10 kPa.

[0009] As a further improvement to the above solution of the present invention, in step S2, the stable sieving of the slurry means that a stable liquid column can be formed between any two adjacent sieves, and the liquid column can form a laminar flow on each of the sieves, and the liquid level on each of the sieves rises uniformly and there is no fluctuation in the liquid level.

[0010] As a further improvement to the above solution of the present invention, in step S3, before counting the number of particles remaining on each of the sieves, it further includes: rinsing each of the sieves with a solvent respectively.

[0011] As a further improvement to the above solution of the present invention, when the slurry is a positive electrode slurry, the solvent is N-methylpyrrolidone (NMP); when the slurry is a negative electrode slurry, the solvent is pure water.

[0012] As a further improvement to the above solution of the present invention, in step S4, evaluating the dispersion performance of the slurry based on the time duration and the number of particles remaining on each of the sieves includes: Calculating the particle size K: K = N1 / M1 + N2 / M2 + … + N n / M n , where N1, N2, …, N n are respectively the number of particles remaining on the n sieves; If the time duration is less than the predetermined time duration and the particle size K is less than the predetermined particle size, then the dispersion performance of the slurry is evaluated as good; otherwise, the dispersion performance of the slurry is evaluated as poor.

[0013] As a further improvement of the above solution of the present invention, the predetermined duration T 预定 is calculated according to the following formula: , where V 预定 is the volume of the slurry that has been stably sieved, t = 15s.

[0014] As a further improvement of the above solution of the present invention, in step S2, the predetermined particle size K 预定 is calculated according to the following formula: ; when the slurry is a positive electrode slurry, k=0.04； when the slurry is a negative electrode slurry, k= 0.08 .

[0015] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention uses sieves with different mesh numbers to sieve the lithium battery slurry to determine the specific number of slurry particles with different particle sizes; uses external negative pressure to achieve rapid and stable sieving of the slurry, and at the same time minimizes the residual slurry during the sieving process of the slurry to avoid affecting the accuracy of counting; and uses the time required for a certain amount of slurry to be stably sieved to evaluate the overall dispersion performance of the slurry. The present invention microscopically evaluates the dispersion performance of the slurry from the size of the particles in the slurry and the distribution of particles of different sizes, and macroscopically evaluates the dispersion performance of the slurry through the stable sieving speed of a certain amount of slurry. Finally, an objective and accurate evaluation system for the dispersion performance of the slurry is achieved through these two-dimensional evaluation indicators, improving the authenticity and accuracy of the dispersion performance of the slurry.

[0016] 2. The present invention detects and evaluates the positive and negative electrode slurries produced in the slurry mixing process during the manufacture of lithium batteries by the method of negative pressure sieving with multi-mesh sieves, achieving a multi-angle evaluation of the dispersion performance of the slurry. It expands from only detecting the size of the largest particle size in the slurry in the prior art to two levels: the number of particles of each particle size at the microscopic level and the stable sieving speed of the slurry at the macroscopic level, which can effectively reduce subsequent process abnormalities caused by poor dispersion performance of the slurry.

[0017] 3. The present invention jointly evaluates the dispersion performance of the slurry by combining the time T required for the slurry to be stably sieved for 100 mL, the residual slurry particles Ni on each mesh sieve, and the particle size K, improving the authenticity and accuracy of the dispersion performance of the slurry.

[0018] 4. The detection equipment used in the present invention is simple, easily available, and inexpensive, which is conducive to popularization and application in actual production. At the same time, it is simple to operate and easy to learn, which is conducive to training production personnel to reach the level of accurate detection. The present invention is applicable to detecting the dispersion performance of various lithium battery slurries, and is not affected by the specific formulation of the slurry and the differences in different material systems. The detection method and evaluation method can be followed, and only the evaluation standard needs to be re-established according to the specific formulation and material system. At the same time, the standard differences of similar slurry formulations and systems are relatively small and can be used for reference. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a flowchart of a method for evaluating the dispersion performance of a slurry proposed by the present invention; Figure 2 is a schematic structural diagram of a sieving system in the present invention; Figure 3 is a graph of the time taken to obtain 100 mL of stable sieving of the positive electrode slurry under different negative pressures; Figure 4 is a graph of the time taken to obtain 100 mL of stable sieving of the negative electrode slurry under different negative pressures; Figure 5 is a graph of the dispersion performance of the positive electrode slurry under different conditions; Figure 6 is a graph of the dispersion performance of the negative electrode slurry under different conditions. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below in conjunction with specific embodiments. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the technical field to which the present invention belongs. The terms used in the specification of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention.

[0022] Referring to Figure 1 , this embodiment proposes a method for evaluating the dispersion performance of a slurry, which includes the following steps: S1. In a negative pressure environment, the slurry is continuously transported to a sieving system formed by a predetermined number of sieves arranged in sequence from top to bottom.

[0023] The pressure of the negative pressure environment is between -15 kPa and -10 kPa, and this negative pressure condition shows good discrimination when evaluating the dispersion performance of different slurries.

[0024] In this embodiment, a negative pressure environment can be created by building a device similar to a Buchner funnel and installing a sieving system inside the device. As shown in Figure 2 , a negative pressure device is externally connected to the bottom of the device through a pipeline to form a continuous and stable negative pressure. It should be noted that the specific negative pressure setting of the externally connected negative pressure device needs to be verified to avoid excessive negative pressure that allows all kinds of slurries to pass through the sieve quickly, or too small negative pressure that makes it difficult for all kinds of slurries to pass through the sieve normally, resulting in the loss of effective resolution of the detection method. And the interface between the negative pressure device and the sealed chamber should avoid the risk of slurry inhalation, which may cause the negative pressure in the chamber to be unstable and affect the evaluation result. The number of sieves of the sieving system is n. From top to bottom, the mesh numbers of the n sieves are M1, M2, …, M n and M1, M2, …, M n increase in sequence. According to the characteristics of the measured slurry and the actual usage requirements, a suitable number of metal sieves with different mesh numbers are set. In this embodiment, n is a positive integer and 3 ≤ n ≤ 5.

[0025] After summarizing the existing design and manufacturing experience, it is found that the particle size of the slurry particles is often in the range of 0.1 mm to 0.25 mm, and the corresponding mesh number of the filter screen used should be in the range of 60 - 150 meshes. Therefore, in this embodiment, the mesh numbers of each sieve are controlled within 60 - 150 meshes.

[0026] When building the sieving system, there should be a certain gap between each layer of sieves to ensure that the slurry can pass through each layer of sieves smoothly without adhesion. The distance between any two adjacent layers of sieves is controlled within 3 - 5 cm. In this embodiment, the distance between any two adjacent layers of sieves is 4 cm.

[0027] Pour the slurry to be evaluated from a position 15 - 20 cm above the top - most sieve and receive the sieved slurry at the bottom of the chamber. In this embodiment, the slurry to be evaluated is poured from a position 15 cm above the top - most sieve (just keep the flow rate stable). This is because too high a height will cause the slurry to splash, and too high a height will make the slurry flow discontinuous, affecting the stability of sieving. And a stable flow rate can avoid the slurry flow being discontinuous and affecting the stability of sieving.

[0028] S2. Start timing after the slurry is stably sieved. When the stably sieved slurry reaches a predetermined amount, stop transporting the slurry and record the duration T required to obtain the predetermined amount of stably sieved slurry.

[0029] To ensure the accuracy of the evaluation, it is necessary to wait for the poured slurry to form a stable sieving process. In this embodiment, the judgment criterion for the stable sieving of the slurry is that a stable liquid column can be formed between any two adjacent sieves, and the liquid column can form a laminar flow on each sieve, and the liquid level on each sieve rises uniformly and there is no fluctuation in the liquid level.

[0030] In this embodiment, the predetermined amount is set to 100 mL. Since the final evaluation of the screening time requires the stable screening of 100 mL of slurry, it is advisable to prepare 200 mL - 300 mL of the slurry to be evaluated before screening. Since it is difficult to determine the cut-off point for the stable screening of 100 mL of slurry, scales can be marked on the receiving container in advance for easy identification.

[0031] S3. Count the number of particles remaining on each sieve.

[0032] After receiving 100 mL of the slurry that has been stably screened and stopping the supply of the slurry to the screening system, there will be slurry that has not been screened remaining on each sieve. To accurately count the number of particles that cannot pass through each sieve, in this embodiment, each sieve is first removed, and then each sieve is rinsed separately with a solvent with a slow flow rate (NMP for the positive electrode slurry and pure water for the negative electrode slurry), and then counted. The number of slurry particles on each mesh sieve needs to be counted separately and the mesh number of the source sieve should be marked for subsequent analysis and evaluation. The number of particles remaining on each sieve can be denoted as N1, N2, …, N n 。

[0033] S4. Evaluate the dispersion performance of the slurry based on the time T and the number of particles remaining on each sieve.

[0034] First, the number of slurry particles is processed using the method of mesh number weighting to obtain the evaluation index particle size K: K = N1 / M1 + N2 / M2 + … + N n / M n 。

[0035] The evaluation of the dispersion performance of the slurry in this embodiment will be jointly evaluated by combining the three indicators of duration T and particle size K: If the duration T is less than the predetermined duration and the particle size K is less than the predetermined particle size, then the dispersion performance of the slurry is evaluated as good; otherwise, the dispersion performance of the slurry is evaluated as poor.

[0036] It should be noted that the evaluation criteria for the two indicators of the time T required to obtain 100 mL of stably screened slurry and the number of slurry particles remaining on each mesh sieve are closely related to the type of slurry, the specific formulation, and the system of the slurry, and corresponding standards need to be used for detailed evaluation. However, the standard differences for similar slurry formulations and systems are relatively small and can be referred to for use.

[0037] Verification Example 1 The purpose of this verification example is to verify the rationality of the negative pressure parameter setting in this embodiment, specifically: A sieving system was built with four layers of sieves (the mesh numbers of each sieve from top to bottom were 80 mesh, 100 mesh, 120 mesh, and 150 mesh, respectively). The positive and negative electrode slurries of a certain type of lithium-ion power battery were sifted and evaluated according to the above method of this embodiment under negative pressure environments of -20 kPa, -15 kPa, -10 kPa, and -5 kPa, respectively, and the time required to obtain 100 mL of stably sieved slurry under each negative pressure environment was obtained. The results are shown in Table 1. Figures 3-4 shown.

[0038] It should be noted that in this verification example, except for the different negative pressures of the external negative pressure equipment used, the rest of the testing equipment and testing personnel are the same, and the positive and negative electrode slurries tested are also from the same source; the slurry is sealed and left to stand, allowing the slurry to settle freely over a certain period of time, in order to obtain slurries with different dispersion properties for testing.

[0039] Table 1

[0040] According to Table 1, Figures 3-4 The results show that: The time T used to obtain 100 mL of stably sieved positive electrode slurry is shorter than the time used to obtain 100 mL of stably sieved negative electrode slurry, which is related to the different system properties of the positive and negative electrode slurries. The results of this verification example are consistent with the actual production experience (the maximum particle size standard of the positive and negative electrodes given by the existing scraper fineness meter detection technology is that the positive electrode slurry is smaller than the negative electrode slurry), indicating that the evaluation of this embodiment can objectively reflect the dispersion performance of the slurry; Under the negative pressure of -5kPa, it takes a long time to obtain 100mL of stable slurry that passes through the screen when the slurry dispersion performance is poor, and the time T used becomes significantly longer as the slurry dispersion performance deteriorates. Therefore, a smaller negative pressure cannot meet the required differentiation required to characterize the slurry dispersion performance by using the time T required to obtain 100mL of stable slurry that passes through the screen; Under the negative pressure of -20kPa, the time required to obtain 100mL of stable sieved slurry is basically the same in the scenario of good slurry dispersion performance, and the time T used varies little in the scenarios of different slurry dispersion performance. Therefore, a larger negative pressure cannot meet the required differentiation required to characterize the slurry dispersion performance by using the time T required to obtain 100mL of stable sieved slurry; Under negative pressure environments of -10kPa and -15kPa, good discrimination was shown in different scenarios of slurry dispersion performance. The time T required to obtain 100mL of stably sieved slurry can be used to characterize the slurry dispersion performance.

[0041] In this verification example, under the same other conditions, by using different negative pressures, the optimal negative pressure for implementing the method of the present invention is found to be between -15 kPa and -10 kPa. Under this negative pressure condition, the time T required to obtain 100 mL of stably sieved slurry can be used to characterize the dispersion performance of the slurry.

[0042] Verification Example 2 The purpose of this verification example is to verify the accuracy of the method of this embodiment, specifically: A sieving system is built with four layers of sieves (the mesh numbers of the sieves from top to bottom are 80 mesh, 100 mesh, 120 mesh, and 150 mesh in sequence). Under a negative pressure environment of -10 kPa, the positive and negative electrode slurries of a certain type of lithium-ion power battery are sieved according to the above method of this embodiment. Record the time T required to obtain 100 mL of stably sieved slurry, count the number of particles on each sieve, and calculate the particle size K. Then, combine the three indicators of time T, the number of particles on each sieve, and particle size K to jointly evaluate the dispersion performance of each slurry. The results are shown in Table 2, Table 3, Figure 5 、 Figure 6 as shown.

[0043] It should be noted that in this verification example, the negative pressure of the external negative pressure equipment used, the detection equipment, and the detection personnel are all the same, and the positive and negative electrode slurries to be detected are also from the same source; the method of sealing and standing the slurry is adopted to enable the slurry to freely settle in a certain time to obtain slurries with different dispersion performances for testing; at the same time, the slurry sampling positions common in the actual production process, namely the slurries at the head and tail of the positive and negative electrode coating machines, the slurries discharged from the transfer tank and the die lip of the coating machine, are also selected for testing.

[0044] Table 2

[0045] Table 3

[0046] According to Table 2, Table 3, Figure 5 、 Figure 6 the results show that: The time T required to obtain 100 mL of stably sieved positive electrode slurry is less than that of the negative electrode slurry under the same conditions, which is consistent with the experience of actual production (the maximum particle size standards of the positive and negative electrodes given by the existing blade fineness meter detection technology are that the positive electrode slurry is smaller than the negative electrode slurry), indicating that this embodiment is consistent with the experience of actual production. It shows that this embodiment can objectively reflect the dispersion performance of the slurry.

[0047] The size and quantity N of the paste particles remaining on the sieves of each mesh number of the positive electrode paste are both smaller than those of the negative electrode paste under the same conditions, which is consistent with the experience in actual production (the maximum particle size standards for the positive and negative electrodes given by the existing blade fineness meter detection technology are that the positive electrode paste is smaller than the negative electrode paste), indicating that this embodiment can objectively reflect the dispersion performance of the paste.

[0048] The particle size K of the positive electrode paste is smaller than that of the negative electrode paste under the same conditions, which is consistent with the experience in actual production (the maximum particle size standards for the positive and negative electrodes given by the existing blade fineness meter detection technology are that the positive electrode paste is smaller than the negative electrode paste), indicating that this embodiment can objectively reflect the dispersion performance of the paste.

[0049] After the positive electrode paste stands for 72 hours, the number of particles N in the paste increases significantly and the particle size K increases significantly. For the negative electrode paste, significant increase occurs and the particle size K increases significantly after standing for 48 hours. This phenomenon is consistent with the phenomena in actual production such as the negative electrode paste being prone to sedimentation, the pressure of the filter increasing, and the pipeline being blocked, indicating that this embodiment can objectively reflect the dispersion performance of the paste.

[0050] The number N of particles in the paste discharged from the die lip of the negative electrode coater is significantly larger and more than that of the positive electrode, and the particle size K is also significantly higher. This phenomenon is consistent with the phenomena in actual production that during the coating process of the negative electrode paste, it is easy to produce particle blockage on the wet film surface of the lip, resulting in scratches, and it is easy to find small particles coated on the film surface to form black spots after roll pressing, indicating that this embodiment can objectively reflect the dispersion performance of the paste.

[0051] Based on past experience and the actual situation of the paste, the detection and evaluation criteria for the method of the present invention can be preliminarily determined: the time T required to obtain 100 mL of stably sieved positive electrode paste is T < 15 s, and the particle size K of the positive electrode paste is K < 0.04; the time T required to obtain 100 mL of stably sieved negative electrode paste is T < 15 s, and the particle size K of the negative electrode paste is K < 0.08.

[0052] In this embodiment, the detection and evaluation criteria of the method of the present invention given are only applicable to the positive and negative electrode pastes under this system formulation and those with similar system formulations. The specific detection and evaluation criteria for pastes under other system formulations should be confirmed with reference to this embodiment before use.

[0053] In summary, the present invention detects and evaluates the positive and negative electrode pastes produced in the paste mixing process during the manufacturing process of lithium batteries by the method of negative pressure sieving through multi-mesh sieves, realizing a multi-angle evaluation of the dispersion performance of the paste. It expands from only detecting the size of the largest particle diameter in the paste in the prior art to two levels: the number of particle diameters at all levels at the microscopic level and the stable sieving speed of the paste at the macroscopic level.

[0054] The present invention combines and evaluates three indicators: the time required to obtain 100 mL of stable sieved slurry, the number of slurry particles remaining on each mesh sieve, and the particle size K, which improves the authenticity and accuracy of the dispersion performance of the slurry.

[0055] The detection equipment used in the present invention is simple to obtain, inexpensive, and conducive to popularization and application in actual production. At the same time, the operation is simple and easy to learn, which is conducive to training production personnel to reach the level of accurate detection.

[0056] The present invention can effectively reduce subsequent process abnormalities caused by poor dispersion performance of the slurry. For example, too large particles will cause sedimentation during slurry storage, transportation, or filtration, increasing the viscosity of the slurry, deteriorating the uniformity, and ultimately blocking the pipeline; larger particles will block at the lip of the coating die head, forming vertical stripes on the coated film surface and reducing the surface density at that place, affecting the performance and interface of the finished battery; while smaller particles will be coated on the film surface, affecting subsequent processes such as rolling and cutting and stacking.

[0057] The present invention is applicable to detecting the dispersion performance of various lithium battery slurries, and is not affected by the specific formulation of the slurry and the differences in different material systems. The detection method and evaluation method can be followed, and only the evaluation criteria need to be re-established according to the specific formulation and material system. At the same time, the standard differences of similar slurry formulations and systems are relatively small and can be referred to.

[0058] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope described in this specification.

[0059] The above-described embodiments only represent several implementation manners of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the invention patent. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several modifications and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the invention patent should be subject to the appended claims.

Claims

1. A method for evaluating the dispersion performance of a slurry, characterized in that: It includes the following steps: S1. Under a negative pressure environment, continuously conveying the slurry to a screening system for screening, wherein the screening system includes a predetermined number of screens arranged in sequence from top to bottom; S2. Start timing after the slurry is stably screened. When the stably screened slurry reaches a predetermined amount, stop conveying the slurry and record the time required to obtain the predetermined amount of stably screened slurry; S3. Count the number of particles remaining on each of the sieves; S4. Evaluate the slurry dispersion performance according to the time length and the number of particles remaining on each of the sieves.

2. The method for evaluating slurry dispersion performance according to claim 1, characterized in that: In the screening system, the number of the screens is n, where n is a positive integer and 3≤n≤5. From top to bottom, the mesh sizes of the n screens are M1, M2, ..., M n And M1, M2, ..., M n Increase successively.

3. The method for evaluating slurry dispersion performance according to claim 2, characterized in that: The mesh number of the sieve is 60-150 meshes; and / or, the vertical distance between any two adjacent sieves is 3-5 cm.

4. The method for evaluating slurry dispersion performance according to claim 1, characterized in that: In step S2, the pressure P of the negative pressure environment satisfies: -15kPa≤P≤-10kPa.

5. The method for evaluating slurry dispersion performance according to claim 1, characterized in that: In step S2, the stable screening of the slurry means that the slurry can form a stable liquid column between any two adjacent screens, and the liquid column can form a laminar flow on each of the screens, and the liquid level on each of the screens rises at a uniform speed without fluctuation.

6. The method for evaluating slurry dispersion performance according to claim 1, characterized in that: In step S3, before counting the number of particles remaining on each of the screens, the step further includes: using a solvent to wash each of the screens respectively.

7. The method for evaluating slurry dispersion performance according to claim 1, characterized in that: When the slurry is a positive electrode slurry, the solvent is N-methylpyrrolidone; when the slurry is a negative electrode slurry, the solvent is pure water.

8. The method for evaluating slurry dispersion performance according to claim 2, characterized in that: In step S4, evaluating the slurry dispersion performance according to the time length and the number of particles remaining on each of the sieves includes: Calculate particle size K: K=N1 / M1+N2 / M2+…+N n / M n , N1, N2, ..., N n are the number of particles remaining on the n sieves respectively; If the time length is less than the predetermined time length and the particle size K is less than the predetermined particle size, the slurry dispersion performance is evaluated to be good; otherwise, the slurry dispersion performance is evaluated to be poor.

9. The method for evaluating slurry dispersion performance according to claim 8, characterized in that: The predetermined time period T 预定 Calculated using the following formula: , where V 预定 To stabilize the volume of the slurry being screened, t =15s.

10. The method for evaluating slurry dispersion performance according to claim 8, characterized in that: In step S2, the predetermined particle size K 预定 Calculated using the following formula: ; When the slurry is a positive electrode slurry, k=0.04； When the slurry is a negative electrode slurry, k=0.08 .

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