Method for rapidly evaluating quality of battery slurry and online preparation method of battery slurry

Abstract

The invention relates to the technical field of battery slurry, in particular to a method for rapidly evaluating the quality of battery slurry and an online preparation method of the battery slurry. The method for rapidly evaluating the quality of the battery slurry comprises the following steps: setting a rotational rheometer to be in a three-stage shear mode, namely a first stage of a variable shear mode with a shear rate from small to large, a second stage of a fixed shear mode with a constant shear rate, and a third stage of a variable shear mode with a shear rate from large to small; carrying out rheological test on the battery slurry sample through a rotational rheometer; the area A of the thixotropic ring is calculated, and whether the battery slurry meets the quality requirement or not is evaluated according to the area A of the thixotropic ring. The detection time is only about 600s, whether excessive dry powder particles exist in the slurry or not and two quality influence factors, namely settling volume after standing, can be evaluated at the same time through a quantitative index, namely the area of the thixotropic ring, and online real-time adjustment of a battery slurry production process is facilitated.

Description

Technical Field

[0001] The present application relates to the technical field of battery slurry, and in particular to a method for quickly evaluating the quality of battery slurry and an online preparation method of battery slurry. Background Art

[0002] In recent years, as environmental problems have become increasingly severe, new energy technologies have ushered in a spring of development. Among the many new energy technologies, lithium-ion batteries have been booming due to their many advantages such as high specific energy and long life. However, in the actual manufacturing of lithium-ion batteries, there are still many problems that need to be solved. The safety and consistency of batteries have always been difficult problems that plague the battery industry. Solving the battery consistency problem starts with the ingredients at the source of battery production. Ingredients are the first step in the production of lithium-ion batteries and the basis for ensuring battery consistency. If the quality of the battery slurry is not good, it will have the following effects on battery performance: (1) inconsistent battery capacity; (2) inconsistent battery internal resistance; (3) poor battery safety performance.

[0003] Generally, there are two basic requirements for battery slurry quality: no dry powder particles in the slurry and low sedimentation after standing. The presence of dry powder particles in the battery slurry will lead to a series of subsequent problems such as inconsistent battery capacity, inconsistent battery internal resistance and poor battery safety performance. High sedimentation after standing will greatly reduce the yield of the battery slurry in the subsequent coating process. However, the evaluation of the two indicators of whether there are excessive dry powder particles in the slurry and the sedimentation after standing in the relevant technical solutions is time-consuming and costly, and cannot achieve the effect of rapid monitoring. In addition, it is impossible to evaluate these two quality requirements with a quantitative indicator, which is not conducive to the online real-time adjustment of the battery slurry production process. Summary of the invention

[0004] In order to solve the above technical problems, the present application provides a method for quickly evaluating the quality of battery slurry and an online preparation method of battery slurry.

[0005] In order to achieve the above-mentioned purpose, according to the first aspect of the present technical solution, the present technical solution provides a method for quickly evaluating the quality of battery slurry.

[0006] According to the method provided in the embodiment of the present application, the method includes:

[0007] The rotational rheometer is set to a three-stage shear mode, the first stage is a variable shear mode with a shear rate from small to large, the second stage is a fixed shear mode with a constant shear rate, and the third stage is a variable shear mode with a shear rate from large to small. The maximum shear rate in the first and second stages is the same as the shear rate in the second stage;

[0008] Rheological tests were performed on battery slurry samples using a rotational rheometer;

[0009] The area ΔA of the thixotropic ring is calculated, and whether the battery slurry meets the quality requirements is evaluated based on the area ΔA of the thixotropic ring.

[0010] Further, in the method for quickly evaluating the quality of battery slurry, the first stage is a shear rate of 0.1S -1 -300S -1 The second stage is a shear rate of 300S -1 The third stage is the shear rate of 300S -1 -0.1S -1 .

[0011] Furthermore, in the method for quickly evaluating the quality of battery slurry, the shearing time of the first stage and the third stage is 300S, and the shearing time of the second stage is 5S.

[0012] Furthermore, in the method for quickly evaluating the quality of battery slurry, the battery slurry is a battery negative electrode slurry. If the thixotropic ring area measured in step 3 satisfies 0≤△A≤a, it is determined that the obtained battery slurry meets the quality requirements, wherein a satisfies 816pa / s≤a≤3000pa / s.

[0013] Furthermore, in the method for quickly evaluating the quality of battery slurry, the battery slurry is a battery positive electrode slurry, and if the thixotropic ring area measured in step 3 satisfies 0≤ΔA, it is determined that the obtained battery slurry meets the quality requirements.

[0014] In order to achieve the above object, according to the second aspect of the present technical solution, the present technical solution provides an online preparation method of battery slurry, which comprises:

[0015] Step 100, dry mixing, kneading and preliminary dispersion are sequentially performed on the raw materials to obtain a prefabricated slurry;

[0016] Step 200, performing high-speed dispersion treatment on the prefabricated slurry in a disperser for a first preset time to make the prefabricated slurry dispersed evenly;

[0017] Step 300, taking a slurry sample after high-speed dispersion treatment, using the method for rapid evaluation of battery slurry quality provided in the first aspect of the present application to measure the thixotropic ring area ΔA and evaluate whether the obtained battery slurry meets the quality requirements.

[0018] Further, the battery slurry is a battery negative electrode slurry; if the thixotropic ring area measured in step 300 satisfies ΔA<0, steps 200 and 300 are executed in a loop until 0≤ΔA≤a, wherein a satisfies 816pa / s≤a≤3000pa / s.

[0019] Furthermore, the battery slurry is a battery negative electrode slurry; if the thixotropic ring area measured in step 300 satisfies 0≤△A≤a, it is determined that the obtained battery slurry meets the quality requirements and the preparation of the battery slurry is completed.

[0020] Furthermore, the battery slurry is a battery negative electrode slurry; if the thixotropic ring area measured in step 300 satisfies ΔA>a, the battery slurry obtained in step 200 is discarded, and the process parameters in steps 100 and 200 are optimized and then re-prepared.

[0021] Further, the battery slurry is a battery positive electrode slurry;

[0022] If the thixotropic ring area measured in step 300 satisfies ΔA<0, then steps 200 and 300 are executed cyclically until ΔA≥0;

[0023] If the thixotropic ring area measured in step 300 satisfies ΔA≥0, it is determined that the obtained battery slurry meets the quality requirements and the preparation of the battery slurry is completed.

[0024] The present invention provides a method for quickly evaluating the quality of battery slurry. The detection time used is only about 600s. The amount of sample required for the rotational rheometer detection is small. The quality of the slurry can be tested synchronously during the battery slurrying process to see if it meets the requirements, and the slurrying process can be quickly adjusted according to the test results. In addition, the method can simultaneously evaluate the presence of excess dry powder particles in the slurry and the amount of sedimentation after standing, two quality influencing factors, through the quantitative index of the thixotropic ring area, simplifying the quality assessment procedure and quickly obtaining the quality assessment results, which is conducive to the online real-time adjustment of the battery slurry production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a viscosity data diagram of the slurry prepared in Example 1 of the present application;

[0026] Figure 2 This is a photo of the coated electrode after the slurry prepared in Example 1 of the present application is applied;

[0027] Figure 3 This is a viscosity data diagram of the slurry prepared in Example 2 of the present application;

[0028] Figure 4 This is a photo of the coated electrode after the slurry prepared in Example 2 of the present application is applied;

[0029] Figure 5 This is a viscosity data diagram of the slurry prepared in Example 3 of the present application;

[0030] Figure 6 This is a photo of the coated electrode after the slurry prepared in Example 3 of the present application is applied;

[0031] Figure 7 This is a viscosity data diagram of the slurry prepared in Example 4 of the present application;

[0032] Figure 8 This is a photo of the coated electrode after the slurry prepared in Example 4 of the present application is applied;

[0033] Fig. 9 This is a viscosity data diagram of the slurry prepared in Example 5 of the present application;

[0034] Fig.10 This is a photo of the coated electrode after the slurry prepared in Example 5 of the present application is applied;

[0035] Fig.11 This is a graph showing the test results of the lateral surface density of the coated electrode after the slurry prepared in Example 5 of the present application is applied;

[0036] Fig.12 This is a viscosity data graph of the slurry prepared in Example 6 of the present application;

[0037] Fig.13 This is a photo of the coated electrode after the slurry prepared in Example 6 of the present application is applied;

[0038] Fig.14 This is a viscosity data diagram of the slurry prepared in Example 7 of the present application;

[0039] Fig.15 This is a photo of the coated electrode after the slurry prepared in Example 7 of the present application is applied;

[0040] Fig.16 This is a viscosity data diagram of the slurry prepared in Example 8 of the present application;

[0041] Fig.17 This is a photo of the coated electrode after the slurry prepared in Example 8 of the present application is applied;

[0042] Fig.18 This is a graph showing the lateral surface density test results of the coated electrode after coating with the slurry prepared in Example 8 of the present application.

[0043] In each viscosity data graph, the horizontal axis represents time (in S), the left vertical axis represents shear stress (in Pa), and the right vertical axis represents viscosity (in mPa·S) DETAILED DESCRIPTION

[0044] The present invention discloses a method for quickly evaluating the quality of battery slurry and an online preparation method for battery slurry. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve it. It is particularly important to point out that all similar substitutions and modifications are obvious to those skilled in the art, and they are all deemed to be included in the present invention. The products, processes and applications described in the present invention have been described through preferred embodiments. Relevant personnel can obviously modify or appropriately change and combine the products, processes and applications described herein without departing from the content, spirit and scope of the present invention to realize and apply the technology of the present invention. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0045] It should be noted that, in this document, relational terms such as "first" and "second", "step 1" and "step 2", and "(1)" and "(2)" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a..." does not exclude the presence of other identical elements in the process, method, article or device comprising the element.

[0046] Hereinafter, preferred embodiments of the present invention will be described in detail.

[0047] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application are clearly and completely described. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in the field without creative work should fall within the scope of protection of the present application.

[0048] A method for quickly evaluating battery slurry quality provided in an embodiment of the present application mainly includes the following steps.

[0049] Step 1, setting the rotational rheometer to a three-stage shear mode, wherein the first stage is a variable shear mode with a shear rate from small to large, the second stage is a fixed shear mode with a constant shear rate, and the third stage is a variable shear mode with a shear rate from large to small, and the maximum shear rate in the first stage and the second stage is the same as the shear rate in the second stage;

[0050] Step 2, performing rheological testing on the battery slurry sample by a rotational rheometer;

[0051] Step 3, calculate the area ΔA of the thixotropic ring, and evaluate whether the battery slurry meets the quality requirements according to the area ΔA of the thixotropic ring. In this step, whether the battery slurry meets the quality requirements mainly examines two indicators, namely whether there are excessive dry powder particles in the slurry and the sedimentation amount of the slurry after standing.

[0052] Among them, in step 1 of the method for quickly evaluating the quality of battery slurry, the first stage of the three-stage shear mode is a shear rate of 0.1S -1 -300S -1 , that is, the shear rate is 0.1S -1 Accelerate evenly to 300S -1 The first stage ends at the end; the second stage is a shear rate of 300S -1 , that is, maintain 300S in the second stage -1 The third stage is a shear rate of 300S -1 -0.1S -1 , that is, the shear rate is increased from 300S -1 Evenly reduce speed to 0.1S -1 The shearing time of the first stage and the third stage is preferably 300S, and the shearing time of the second stage is preferably 5S.

[0053] In some embodiments, the battery slurry used in the method for quickly evaluating the quality of battery slurry is a battery negative electrode slurry. If the thixotropic ring area measured in step 3 satisfies 0≤△A≤a, the obtained battery slurry is determined to meet the quality requirements, where a satisfies 816pa / s≤a≤3000pa / s. That is, for the battery negative electrode slurry, when 0≤△A≤a, it is determined that there are no excessive dry powder particles in the slurry, and the sedimentation of the slurry after standing meets the quality requirements; when △A<0, there are excessive dry powder particles in the slurry so that the slurry quality cannot meet the quality requirements; when △A>a, the sedimentation of the slurry after standing is large, and the recovery ability of the slurry after shearing is poor, resulting in the slurry failing to meet the quality requirements.

[0054] In some embodiments, the battery slurry used in the method for quickly evaluating the quality of battery slurry is a positive electrode slurry of a battery. If the thixotropic ring area measured in step 3 satisfies 0≤△A, the obtained battery slurry is determined to meet the quality requirements. That is, for the negative electrode slurry of the battery, when 0≤△A, it is determined that there are no excessive dry powder particles in the slurry, and the sedimentation amount of the slurry after standing meets the quality requirements; when △A<0, the slurry quality cannot meet the quality requirements due to the presence of excessive dry powder particles in the slurry.

[0055] The detection time of the method for quickly evaluating the battery slurry quality in the embodiment of the present application is only about 600 seconds, and the amount of sample required for the rotational rheometer detection is small. The slurry quality can be tested synchronously during the battery slurrying process to see if it meets the requirements, and the slurrying process can be quickly adjusted according to the test results.

[0056] In addition, the method for quickly evaluating the quality of battery slurry in the embodiment of the present application can simultaneously evaluate two quality influencing factors, namely, whether there are excess dry powder particles in the slurry and the amount of sedimentation after standing, through the thixotropic ring area, a quantitative indicator. This simplifies the quality evaluation procedure and can quickly obtain quality evaluation results, which is beneficial to the online real-time adjustment of the battery slurry production process.

[0057] The embodiment of the present invention also correspondingly protects an online preparation method of battery slurry, and the online preparation method of battery slurry mainly includes the following steps.

[0058] Step 100, dry mixing, kneading and preliminary dispersion are sequentially performed on the raw materials to obtain a prefabricated slurry;

[0059] Step 200, performing high-speed dispersion treatment on the prefabricated slurry in a disperser for a first preset time to make the prefabricated slurry dispersed evenly;

[0060] Step 300, taking a slurry sample after high-speed dispersion treatment, using the method for quickly evaluating battery slurry quality provided in the above embodiment to measure the thixotropic ring area ΔA and evaluate whether the obtained battery slurry meets the quality requirements.

[0061] In some embodiments, the battery slurry prepared by the online preparation method of battery slurry is a battery negative electrode slurry.

[0062] If the thixotropic ring area measured in step 300 satisfies 0≤△A≤a, it is determined that the obtained battery slurry meets the quality requirements, that is, it is determined that there are no excessive dry powder particles in the slurry, and the sedimentation amount of the slurry after standing meets the quality requirements. The battery slurry is prepared and can be directly used in the subsequent coating process.

[0063] If the thixotropic ring area measured in step 300 satisfies ΔA<0, then steps 200 and 300 are cyclically executed until 0≤ΔA≤a, where a satisfies 816pa / s≤a≤3000pa / s. When ΔA<0, it indicates that there are excessive dry powder particles in the slurry, so that the slurry quality cannot meet the quality requirements. It is only necessary to cyclically execute step 200 for continued stirring and step 300 for online detection. As the number of executions of step 200 increases, the dry powder particles in the slurry can be gradually reduced.

[0064] If the thixotropic ring area measured in step 300 satisfies; if the thixotropic ring area measured in step 300 satisfies △A>a, the battery slurry obtained in step 200 is discarded, and the process parameters in steps 100 and 200 are optimized and re-prepared. When △A>a, it means that the sedimentation of the battery slurry after standing is large, which makes the slurry unable to be used in the subsequent coating process, resulting in a significant decrease in the yield rate of the coating process. In addition, the deterioration of the sedimentation index is usually due to the unreasonable setting of the process parameters in steps 100 and 200, such as stirring time, stirring intensity, etc., which leads to the structural destruction of the binder. Once it occurs, the current slurry cannot be remedied to make its sedimentation meet the standard, and the process parameters in the aforementioned steps need to be adjusted and optimized. Therefore, the online preparation method of the battery slurry of the present application can also quickly judge the unreasonable pulping process.

[0065] In some embodiments, the battery slurry prepared by the online preparation method of battery slurry is a battery positive electrode slurry.

[0066] If the thixotropic ring area measured in step 300 satisfies △A≥0, it is determined that the obtained battery slurry meets the quality requirements, that is, it is determined that there are no excessive dry powder particles in the slurry, and the sedimentation amount of the slurry after standing meets the quality requirements, and it can be directly used in the subsequent coating process, and the preparation of the battery slurry is completed.

[0067] If the thixotropic ring area measured in step 300 satisfies ΔA<0, then steps 200 and 300 are executed cyclically until ΔA≥0. When ΔA<0, it indicates that there are excessive dry powder particles in the slurry, so that the slurry quality cannot meet the quality requirements. It is only necessary to cyclically execute step 200 to continue stirring and step 300 to perform online detection. As the number of executions of step 200 increases, the dry powder particles in the slurry can be gradually reduced.

[0068] Example 1

[0069] The negative electrode slurry is made with the following mass ratio of each raw material: graphite (KD-1): SP: CMC: water-based glue: SBR: plasticizer = 96.7: 0.8: 0.5: 1.3: 0.7: 0.4. The detailed slurry production process is as follows:

[0070] (1) Graphite, SP and CMC were mixed according to the mass ratio and dry-mixed for 45 minutes according to the process parameters of rotation of 300 rpm and revolution of 20 rpm;

[0071] (2) A certain proportion of water-based glue and ultrapure water are premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 73%, and kneaded for 10 minutes according to the process parameters of rotation 300 rpm and revolution 20 rpm;

[0072] (3) A certain proportion of water-based glue and ultrapure water were premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 63%, and stirred for 60 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm;

[0073] (4) adding ultrapure water and plasticizer, adjusting the solid content to 53%, stirring for 60 min according to the process parameters of rotation 1816 rpm and revolution 20 rpm, and testing the viscosity, the viscosity range is 4000 Pa / s to 6000 Pa / s;

[0074] (5) Add SBR and stir slowly for 30 min according to the process parameters of rotation 300 rpm and revolution 20 rpm.

[0075] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Figure 1 As shown, the prepared slurry sample was retained to test the slurry static viscosity change for 0 to 48 hours. The data on the thixotropic ring area and the slurry static viscosity change are shown in Table 1.

[0076] Table 1

[0077]

[0078] The slurry prepared in Example 1 was subjected to a coating process for the electrode, and the coating electrode effect was obtained as follows: Figure 2 As shown, it can be seen that there are obvious scratches on the coated electrode, which is caused by the presence of incompletely dispersed dry powder particles in the slurry.

[0079] Example 2

[0080] The negative electrode slurry is made with the following mass ratio of each raw material: graphite (KD-1): SP: CMC: water-based glue: SBR: plasticizer = 96.7: 0.8: 0.5: 1.3: 0.7: 0.4. The detailed slurry production process is as follows:

[0081] (1) Graphite, SP and CMC were mixed according to the mass ratio and dry-mixed for 45 minutes according to the process parameters of rotation of 300 rpm and revolution of 20 rpm;

[0082] (2) A certain proportion of water-based glue and ultrapure water are premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 73%, and kneaded for 30 minutes according to the process parameters of rotation 300 rpm and revolution 20 rpm;

[0083] (3) A certain proportion of water-based glue and ultrapure water were premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 63%, and stirred for 90 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm;

[0084] (4) adding ultrapure water and plasticizer, adjusting the solid content to 53%, stirring for 60 min according to the process parameters of rotation 1816 rpm and revolution 20 rpm, and testing the viscosity, the viscosity range is 4000 Pa / s to 6000 Pa / s;

[0085] (5) Add SBR and stir slowly for 30 min according to the process parameters of rotation 300 rpm and revolution 20 rpm.

[0086] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Figure 3 As shown, the prepared slurry samples were retained to test the slurry static viscosity change for 0 to 48 hours. The data on the thixotropic ring area and the slurry static viscosity change are shown in Table 2.

[0087] Table 2

[0088]

[0089] The slurry prepared in Example 2 is subjected to a coating process for the electrode, and the coating electrode effect is as follows: Figure 4 As shown, it can be seen that there are no obvious scratches on the coated electrode, indicating that there are no incompletely dispersed dry powder particles in the slurry.

[0090] Example 3

[0091] The negative electrode slurry is made with the following mass ratio of each raw material: graphite (KD-1): SP: CMC: water-based glue: SBR: plasticizer = 96.7: 0.8: 0.5: 1.3: 0.7: 0.4. The detailed slurry production process is as follows:

[0092] (1) Graphite, SP and CMC were mixed according to the mass ratio and dry-mixed for 45 minutes according to the process parameters of rotation of 300 rpm and revolution of 20 rpm;

[0093] (2) A certain proportion of water-based glue and ultrapure water are premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 73%, and kneaded for 30 minutes according to the process parameters of rotation 300 rpm and revolution 20 rpm;

[0094] (3) A certain proportion of water-based glue and ultrapure water were premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 63%, and stirred for 120 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm;

[0095] (4) adding ultrapure water and plasticizer, adjusting the solid content to 53%, stirring for 60 min according to the process parameters of rotation 1816 rpm and revolution 20 rpm, and testing the viscosity, the viscosity range is 4000 Pa / s to 6000 Pa / s;

[0096] (5) Add SBR and stir slowly for 30 min according to the process parameters of rotation 300 rpm and revolution 20 rpm.

[0097] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Figure 5 As shown, the prepared slurry sample was retained to test the slurry static viscosity change for 0 to 48 hours. The data on the thixotropic ring area and the slurry static viscosity change are shown in Table 3.

[0098] Table 3

[0099]

[0100] The slurry obtained in Example 3 was subjected to a coating process for the electrode, and the coating electrode effect was obtained as follows: Figure 6 As shown, it can be seen that there are no obvious scratches on the coated electrode, indicating that there are no incompletely dispersed dry powder particles in the slurry.

[0101] Example 4

[0102] The negative electrode slurry is made with the following mass ratio of each raw material: graphite (KD-1): SP: CMC: water-based glue: SBR: plasticizer = 96.7: 0.8: 0.5: 1.3: 0.7: 0.4. The detailed slurry production process is as follows:

[0103] (1) Graphite, SP and CMC were mixed according to the mass ratio and dry-mixed for 45 minutes according to the process parameters of rotation of 300 rpm and revolution of 20 rpm;

[0104] (2) A certain proportion of water-based glue and ultrapure water are premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 73%, and kneaded for 30 minutes according to the process parameters of rotation 300 rpm and revolution 20 rpm;

[0105] (3) A certain proportion of water-based glue and ultrapure water were premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 63%, and stirred for 180 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm;

[0106] (4) adding ultrapure water and plasticizer, adjusting the solid content to 53%, stirring for 60 min according to the process parameters of rotation 1816 rpm and revolution 20 rpm, and testing the viscosity, the viscosity range is 4000 Pa / s to 6000 Pa / s;

[0107] (5) Add SBR and stir slowly for 30 min according to the process parameters of rotation 300 rpm and revolution 20 rpm.

[0108] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Figure 7 As shown, the prepared slurry sample was retained to test the slurry static viscosity change for 0 to 48 hours. The data on the thixotropic ring area and the slurry static viscosity change are shown in Table 4.

[0109] Table 4

[0110]

[0111] The slurry obtained in Example 4 was subjected to a coating process for the electrode, and the coating electrode effect was obtained as follows: Figure 8 As shown, it can be seen that there are no obvious scratches on the coated electrode, indicating that there are no incompletely dispersed dry powder particles in the slurry.

[0112] Example 5

[0113] The negative electrode slurry is made with the following mass ratio of each raw material: graphite (KD-1): SP: CMC: water-based glue: SBR: plasticizer = 96.7: 0.8: 0.5: 1.3: 0.7: 0.4. The detailed slurry production process is as follows:

[0114] (1) Graphite, SP and CMC were mixed according to the mass ratio and dry-mixed for 45 minutes according to the process parameters of rotation of 300 rpm and revolution of 20 rpm;

[0115] (2) A certain proportion of water-based glue and ultrapure water are premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 73%, and kneaded for 30 minutes according to the process parameters of rotation 300 rpm and revolution 20 rpm;

[0116] (3) A certain proportion of water-based glue and ultrapure water were premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 63%, and stirred for 180 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm;

[0117] (4) adding ultrapure water and plasticizer, adjusting the solid content to 53%, stirring for 120 min according to the process parameters of rotation 2500 rpm and revolution 20 rpm, and testing the viscosity, the viscosity range is 4000 Pa / s to 6000 Pa / s;

[0118] (5) Add SBR and stir slowly for 30 min according to the process parameters of rotation 300 rpm and revolution 20 rpm.

[0119] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Fig. 9 As shown, the prepared slurry samples were retained to test the slurry static viscosity change for 0 to 48 hours. The data on the thixotropic ring area and the slurry static viscosity change are shown in Table 5.

[0120] Table 5

[0121]

[0122] The slurry obtained in Example 5 was subjected to a coating process for the electrode, and the coating electrode effect was obtained as follows: Fig.10 As shown, it can be seen that there are no obvious scratches on the coated electrode, indicating that there are no incompletely dispersed dry powder particles in the slurry, but the electrode edge bulges after coating. The bulge will directly lead to lithium deposition in the battery, affecting the life and safety of the manufactured battery.

[0123] The surface density of each position of the coated electrode is measured by uniformly taking points in the horizontal direction. The measured data of the surface density at each position and the coating standard data refer to Fig.11 It can be seen that the uniformity of the transverse surface density after coating is poor, showing that the middle is light and the two sides are thin, and the coating thickness is inconsistent (the normal transverse surface density deviation is less than 0.5g / m 2 ) This is because the thixotropic ring area of ​​the slurry is too large, and the recovery energy of the slurry is weak after the slurry is sheared, which affects the uniformity of the coating and the consistency of the coating thickness, mainly manifested in the poor uniformity of the lateral surface density after coating. It can also be seen from Table 5 that the static viscosity of the slurry from 0 to 48 hours is very high, and the recovery energy of the slurry will be relatively weak after the slurry is sheared.

[0124] Example 6

[0125] The negative electrode slurry is made with the following mass ratio of each raw material: graphite (K6): SP: CMC: water-based glue: SBR: plasticizer = 96.7: 0.8: 0.5: 1.3: 0.7: 0.4. The detailed slurry production process is as follows:

[0126] (1) Graphite, SP and CMC were mixed according to the mass ratio and dry-mixed for 45 minutes according to the process parameters of rotation of 300 rpm and revolution of 20 rpm;

[0127] (2) A certain proportion of water-based glue and ultrapure water are premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 73%, and kneaded for 30 minutes according to the process parameters of rotation 300 rpm and revolution 20 rpm;

[0128] (3) A certain proportion of water-based glue and ultrapure water were premixed in a mass ratio of 1:2 and then added to the slurry to adjust the solid content of the slurry to about 63%, and stirred for 120 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm;

[0129] (4) adding ultrapure water and plasticizer, adjusting the solid content to 53%, stirring for 60 min according to the process parameters of rotation 1816 rpm and revolution 20 rpm, and testing the viscosity, the viscosity range is 4000 Pa / s to 6000 Pa / s;

[0130] (5) Add SBR and stir slowly for 30 min according to the process parameters of rotation 300 rpm and revolution 20 rpm.

[0131] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Fig.12 As shown, the prepared slurry samples were retained to test the slurry static viscosity change for 0 to 48 hours. The data on the thixotropic ring area and the slurry static viscosity change are shown in Table 6.

[0132] Table 6

[0133]

[0134] The slurry obtained in Example 6 was subjected to a coating process for the electrode, and the coating electrode effect was obtained as follows: Fig.13 As shown, it can be seen that there are obvious scratches on the coated electrode, indicating that there are incompletely dispersed dry powder particles in the slurry.

[0135] The negative electrode slurry prepared in Examples 1-6 of the present invention was tested for thixotropic rings. The negative electrode slurry is a water-based slurry, and its wettability is affected to a certain extent. There may be undispersed dry powder particles. When the thixotropic ring area is a negative value, it corresponds to the presence of incompletely dispersed dry powder particles in the negative electrode slurry. And in the negative electrode slurry in the range of 0<ΔA≤816Pa / s, there are no incompletely dispersed dry powder particles, and the static viscosity of the slurry from 0 to 48h is low, and there is no bulging edge phenomenon in the coated electrode obtained in the coating process, indicating that the slurry has good recovery ability after shearing. However, if the thixotropic ring area is too large, the recovery ability of the slurry after shearing will be poor, which will lead to uneven thickness and bulging edges of the coating edges, and the static viscosity of the slurry from 0 to 48h is too high, such as Example 5. For the negative electrode slurry, the technicians further discovered that when the thixotropic ring area is 816Pa / s<ΔA≤3000Pa / s, the recovery ability of the negative electrode slurry after shearing after coating will be slightly worse than when ΔA≤816Pa / s, but it can still meet the process requirements. However, when ΔA>3000Pa / s, the recovery ability of the slurry after shearing after coating is too poor, which will cause uneven thickness and bulging edge of the coating, and cannot meet the use requirements.

[0136] Example 7

[0137] The positive electrode slurry is prepared with the following mass ratio of each raw material: lithium iron (E80): conductive agent SP: conductive slurry: PVDF: PVP = 96.8: 0.7: 0.3: 2.2: 0.1. The detailed slurry preparation process is as follows:

[0138] (1) NMP and PVDF were mixed, the solid content was adjusted to 6.5%, and the mixture was stirred for 30 min according to the process parameters of rotation of 500 rpm and revolution of 10 rpm, and then stirred for 360 min according to the process parameters of rotation of 2000 rpm and revolution of 20 rpm.

[0139] (2) Add SP and stir for 10 min at a rotation speed of 500 rpm and an orbital speed of 10 rpm, then stir for 120 min at a rotation speed of 2000 rpm and an orbital speed of 20 rpm.

[0140] (3) Add the conductive slurry and stir for 60 minutes according to the process parameters of rotation 2000 rpm and revolution 20 rpm.

[0141] (4) Add half of the iron-lithium main material and a certain amount of NMP, adjust the solid content to 56.55%, and stir for 30 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm.

[0142] (5) Add the remaining half of the iron-lithium main material and PVP, adjust the solid content to 72%, and stir for 30 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm.

[0143] (6) A certain amount of NMP was added to adjust the solid content to 67%, and the mixture was stirred for 60 min according to the process parameters of rotation at 2500 rpm and revolution at 25 rpm.

[0144] (7) NMP was added to adjust the solid content to 63%, and the mixture was stirred for 60 min at a rotation speed of 2500 rpm and a revolution speed of 25 rpm.

[0145] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Fig.14 As shown, the prepared slurry samples were retained to test the slurry static viscosity change for 0 to 48 hours. The data on the thixotropic ring area and the slurry static viscosity change are shown in Table 7.

[0146] Table 7

[0147]

[0148] The slurry obtained in Example 7 was subjected to a coating process for the electrode, and the coating electrode effect was obtained as follows: Fig.15 As shown, it can be seen that there are no obvious scratches on the coated electrode, indicating that there are no incompletely dispersed dry powder particles in the slurry.

[0149] Example 8

[0150] The positive electrode slurry is prepared with the following mass ratio of each raw material: lithium iron (E80): conductive agent SP: conductive slurry: PVDF: PVP = 96.8: 0.7: 0.3: 2.2: 0.1. The detailed slurry preparation process is as follows:

[0151] (1) Iron lithium (E80), SP, and PVDF were mixed and dry-mixed for 45 minutes according to the process parameters of rotation of 300 rpm and revolution of 20 rpm;

[0152] (2) adding a certain amount of NMP to adjust the solid content of the slurry to about 82%, and kneading for 30 minutes according to the process parameters of rotation 300 rpm and revolution 20 rpm;

[0153] (3) adding a certain amount of NMP and conductive slurry to adjust the solid content of the slurry to about 73%, and stirring for 60 minutes according to the process parameters of rotation 500 rpm and revolution 20 rpm;

[0154] (4) NMP and PVP were added, and the solid content was adjusted to 53%. The mixture was stirred for 180 min according to the process parameters of rotation of 2500 rpm and revolution of 20 rpm. The viscosity was tested and the viscosity range was 4000 Pa / s to 10000 Pa / s.

[0155] The method for quickly evaluating the quality of battery slurry provided in the embodiment of the present application is used to test the thixotropic ring area of ​​the discharged material. The rheological data during the test are as follows: Fig.16 As shown, the prepared slurry samples were retained to test the change in slurry static viscosity for 0 to 48 hours. The data on the change in thixotropic ring area and slurry static viscosity are shown in Table 8.

[0156] Table 8

[0157]

[0158] The slurry obtained in Example 8 was subjected to a coating process for the electrode, and the coating electrode effect was obtained as follows: Fig.17 As shown, it can be seen that there are no obvious scratches on the coated electrode, indicating that there are no incompletely dispersed dry powder particles in the slurry, but the electrode has a bulging edge after coating ( Fig.17 The bulging edge will directly lead to lithium deposition in the battery, affecting the life and safety of the battery.

[0159] The surface density of each position of the coated electrode is measured by uniformly taking points in the horizontal direction. The measured data of the surface density at each position and the coating standard data refer to Fig.18 It can be seen that the uniformity of the transverse surface density after coating is poor. This is because the area of ​​the thixotropic ring of the slurry is too large, and the recovery energy of the slurry after shearing is weak, which affects the uniformity of coating and the consistency of coating thickness, which is mainly manifested in the poor uniformity of the transverse surface density and the bulging edge after coating. It can also be seen from Table 8 that the static viscosity of the slurry from 0 to 48 hours is very high, indicating that the recovery energy of the slurry after shearing will be relatively weak.

[0160] In Examples 7 and 8 of the present invention, positive electrode slurry is prepared by dry-wet mixing process to test the thixotropic ring. The positive electrode slurry is an oil-based slurry with good wettability. Generally, there are no undispersed dry powder particles, and the thixotropic ring area is generally positive. Example 7 adopts a wet mixing process, and Example 8 adopts a dry process. The dispersion and dissolution effects of the binder under different mixing processes are different, which will lead to differences in the recovery energy of the positive electrode slurry. The technicians further explored the experiment outside of Examples 7 and 8 and found that the thixotropic ring area is too large, which will lead to poor recovery ability of the slurry after shearing, which will lead to uneven thickness and bulging edge of the coating. For the positive electrode slurry, the technicians found that when the thixotropic ring area ΔA>8500Pa / s, there is a problem of poor recovery ability of the positive electrode slurry after shearing and too high static viscosity of the slurry for 0 to 48h. The recovery ability of the slurry can be judged from the area of ​​the thixotropic ring of the positive electrode slurry, thereby judging whether the binder is fully dissolved and dispersed, and improving the stirring process through real-time test results to reduce slurry scrapping.

[0161] Some embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other.

[0162] The foregoing is merely a specific embodiment of the present invention, which enables those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for quickly evaluating the quality of battery slurry, characterized in that: include: The rotational rheometer is set to a three-stage shear mode, the first stage is a variable shear mode with a shear rate from small to large, the second stage is a fixed shear mode with a constant shear rate, and the third stage is a variable shear mode with a shear rate from large to small. The maximum shear rate in the first and second stages is the same as the shear rate in the second stage; Rheological tests were performed on battery slurry samples using a rotational rheometer; The area ΔA of the thixotropic ring is calculated, and whether the battery slurry meets the quality requirements is evaluated based on the area ΔA of the thixotropic ring.

2. The method for rapidly evaluating battery slurry quality according to claim 1, characterized in that: The first stage is a shear rate of 0.1S -1 -300S -1 The second stage is a shear rate of 300S -1 The third stage is the shear rate of 300S -1 -0.1S -1 .

3. The method for rapidly evaluating battery slurry quality according to claim 2, characterized in that: The shearing time of the first and third stages is 300S, and the shearing time of the second stage is 5S.

4. The method for rapidly evaluating battery slurry quality according to any one of claims 1 to 3, characterized in that: The battery slurry is a battery negative electrode slurry. If the thixotropic ring area measured in step 3 satisfies 0≤△A≤a, it is determined that the obtained battery slurry meets the quality requirements, wherein a satisfies 816pa / s≤a≤3000pa / s.

5. The method for rapidly evaluating battery slurry quality according to any one of claims 1 to 3, characterized in that: The battery slurry is a battery positive electrode slurry. If the thixotropic ring area measured in step 3 satisfies 0≤ΔA, it is determined that the obtained battery slurry meets the quality requirements.

6. An online preparation method for battery slurry, characterized in that: include: Step 100, dry mixing, kneading and preliminary dispersion are sequentially performed on the raw materials to obtain a prefabricated slurry; Step 200, performing high-speed dispersion treatment on the prefabricated slurry in a disperser for a first preset time to make the prefabricated slurry dispersed evenly; Step 300, taking a slurry sample after high-speed dispersion treatment, measuring the thixotropic ring area ΔA using the method for rapid evaluation of battery slurry quality as claimed in any one of claims 1 to 3, and evaluating whether the obtained battery slurry meets the quality requirements.

7. The online preparation method of battery slurry according to claim 6, characterized in that: The battery slurry is a battery negative electrode slurry; if the thixotropic ring area measured in step 300 satisfies ΔA<0, steps 200 and 300 are executed cyclically until 0≤ΔA≤a, where a satisfies 816pa / s≤a≤3000pa / s.

8. The online preparation method of battery slurry according to claim 6, characterized in that: The battery slurry is a battery negative electrode slurry; if the thixotropic ring area measured in step 300 satisfies 0≤ΔA≤a, it is determined that the obtained battery slurry meets the quality requirements and the preparation of the battery slurry is completed.

9. The online preparation method of battery slurry according to claim 6, characterized in that: The battery slurry is a battery negative electrode slurry; if the thixotropic ring area measured in step 300 satisfies ΔA>a, the battery slurry obtained in step 200 is discarded, and the process parameters in steps 100 and 200 are optimized and then re-prepared.

10. The on-line preparation method of battery slurry according to claim 6, characterized in that: The battery slurry is a battery positive electrode slurry; If the thixotropic ring area measured in step 300 satisfies ΔA<0, then steps 200 and 300 are executed cyclically until ΔA≥0; If the thixotropic ring area measured in step 300 satisfies ΔA≥0, it is determined that the obtained battery slurry meets the quality requirements and the preparation of the battery slurry is completed.

Images