Method for evaluating lithium-ion battery slurry uniformity and method for preparing lithium-ion battery slurry

Abstract

The application relates to the field of lithium ion batteries, and relates to a method for evaluating the uniformity of lithium ion battery slurry and a preparation method of lithium ion battery slurry. The method comprises the following steps: in the process of homogenizing, the change rate of the surface tension of the slurry is monitored at preset time intervals; if the change rate of the surface tension is within the range corresponding to the preset time interval, the lithium ion battery slurry is uniformly dispersed. The method utilizes the characteristic differences of different slurry states, monitors the change rate of the surface tension of the slurry every certain period of time, and if the change rate of the surface tension is within the range corresponding to the preset time interval, the lithium ion battery slurry is uniformly dispersed. By the method, excessive stirring can be avoided, the battery production process time is shortened, the battery production efficiency is improved, the uniformity of the lithium ion battery slurry can be effectively and accurately obtained, the evaluation cycle of the battery slurry is shortened, and the reliability of the evaluation data is enhanced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of lithium ion batteries, in particular, to a method for evaluating the uniformity of lithium ion battery slurry and a method for preparing lithium ion battery slurry. BACKGROUND

[0002] Currently, commercially available lithium ion batteries are usually composed of single cells into modules or packs to meet the voltage or capacity needs of the equipment, so the battery manufacturers need to produce high-quality and consistent batteries. If the battery consistency is poor, the battery is prone to thermal runaway during use, which can cause the battery to catch fire or explode, posing a great risk. Therefore, battery consistency is one of the important indicators of battery performance. Solving the problem of battery consistency starts from the source of battery production, i.e., the preparation of slurry.

[0003] Battery slurry is a slurry system composed of different materials. The mixed slurry is ready for the next process, and the mixed materials of the coated slurry must be uniformly dispersed. Lithium ion battery slurry needs to have good uniformity and stability, which is an important indicator to ensure the consistency of the battery in the battery production process. Therefore, it is very important to detect and control the uniformity of the battery slurry.

[0004] The binder is one of the important components of the battery slurry. The binder is added during the preparation of the battery slurry to bond the active material particles of the battery. More importantly, the binder can firmly bond the active material to the current collector. In order to increase the conductivity of the battery material, a conductive agent is added during the mixing and preparation of the battery. In the slurry process containing the conductive agent, the binder will be adsorbed and flocculated by the conductive agent in large quantities. In the slurry process without the conductive agent, the binder will be adsorbed and flocculated by the main material in large quantities. Therefore, it is easy to cause the overall uneven dispersion of the battery slurry.

[0005] The conventional monitoring methods include testing the flowability, viscosity, solid content, and particle size of the slurry. However, these testing methods are relatively rough and cannot accurately characterize the physical characteristics of the uniformity of the battery slurry. At the same time, the above methods take a long time to test, which takes several hours or even longer. Therefore, these methods do not have the significance of guiding quality control for the production process. SUMMARY

[0006] The purpose of the embodiments of the present application is to provide a method for evaluating the uniformity of lithium ion battery slurry and a method for preparing lithium ion battery slurry.

[0007] In a first aspect, the present application provides a method for evaluating the uniformity of lithium ion battery slurry, comprising:

[0008] During the homogenization process, the surface tension change rate of the slurry is monitored at a predetermined time interval. If the surface tension change rate is within the range corresponding to the predetermined time interval, the lithium ion battery slurry is uniformly dispersed.

[0009] The method utilizes the difference in characteristics of different slurries, monitors the surface tension change rate of the slurry at intervals, and if the surface tension change rate is within the range corresponding to the preset time interval, the lithium ion battery slurry is uniformly dispersed. By this method, excessive stirring can be avoided, the battery production process time can be shortened, the battery production efficiency can be improved, and the uniformity of the lithium ion battery slurry can be effectively and accurately obtained, the evaluation cycle of the battery slurry can be shortened, and the reliability of the evaluation data can be enhanced.

[0010] In other embodiments of the present application, the surface tension change rate of the slurry is monitored at preset time intervals, including:

[0011] The surface tension value of the corresponding sample is detected, and the surface tension change rate of the sample at adjacent time intervals is calculated.

[0012] In other embodiments of the present application, the sample is taken at preset time intervals, including:

[0013] The sample is taken once every equal interval of time; optionally, the interval time is 10-90 minutes.

[0014] In other embodiments of the present application, the surface tension change rate of the sample at adjacent time intervals is calculated, including:

[0015] According to formula (1):

[0016]

[0017] In formula (1), χ represents the surface tension change rate;

[0018] γ1 represents the surface tension value of the previous battery slurry;

[0019] γ2 represents the surface tension value of the next battery slurry.

[0020] In other embodiments of the present application, the surface tension value of the corresponding sample is detected, including:

[0021] The surface tension value of the sample is tested by a contact angle tester.

[0022] In other embodiments of the present application, the surface tension value of the sample is tested by a contact angle tester, including:

[0023] The surface tension value of each sample is measured by the pendant drop method.

[0024] In other embodiments of the present application, the surface tension value of each sample is measured by the pendant drop method, including:

[0025] The flat needle is used for suspension drop, the outer diameter of the flat needle is 0.5-2.0mm; the value of gravity acceleration is 9.78822, the ideal value of drop B factor is 0.4-0.6; the titration volume is 4-8ul, the titration rate is 2-3ml / min, and the lens view angle is 0°.

[0026] In other embodiments of the present application, the homogenate comprises:

[0027] The raw materials for preparing the lithium ion battery slurry are mixed and stirred;

[0028] Optionally, the raw materials for preparing the lithium ion battery slurry comprise: positive active material, conductive agent, binder, dispersant, water; or negative active material, conductive agent, binder, water;

[0029] Optionally, the positive active material comprises at least one of lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium-rich material or lithium manganese oxide positive material.

[0030] Optionally, the negative active material comprises at least one of alloy negative material, graphite, lithium titanate, silicon-carbon material, hard carbon material or silicon-oxygen material.

[0031] Optionally, the conductive agent comprises at least one of Super-P, KS-6, conductive carbon black, acetylene black or CNT.

[0032] In other embodiments of the present application, the solid content of the lithium ion battery slurry is 50%-90%.

[0033] In a second aspect, the present application provides a preparation method of lithium ion battery slurry, which is evaluated by using the aforementioned evaluation method of uniformity of lithium ion battery slurry.

[0034] When the lithium ion battery slurry is evaluated to be uniformly dispersed, the total time for uniform material is calculated, and then the time is used as the uniform material time for preparing the lithium ion battery slurry. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme in the embodiments of the present application will be described clearly and completely below. Obviously, the described embodiments are part of the embodiments of the present application, but not all the embodiments.

[0036] Therefore, the following detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but only represents selected embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of the present application.

[0037] The inventors found that the characteristics of the slurry in different stages of the preparation process are different, and the smaller the difference is, the better the uniformity of the stirred slurry is. Therefore, samples in the preparation process of the battery slurry are taken at different time intervals to test the surface tension thereof; through unified measurement conditions and calculation theory, the change rate of the surface tension difference obtained at different time intervals can be used to evaluate the uniformity of the stirring of the slurry.

[0038] Based on this finding, the embodiments of the present application provide a method for evaluating the uniformity of a lithium ion battery slurry, comprising:

[0039] In the process of homogenization, the change rate of the surface tension of the slurry is monitored at a preset time interval, and if the change rate of the surface tension is within the range corresponding to the preset time interval, the lithium ion battery slurry is uniformly dispersed.

[0040] The method utilizes the characteristic differences of different slurry states, monitors the change rate of the surface tension of the slurry at regular time intervals, and if the change rate of the surface tension is within the range corresponding to the preset time interval, the lithium ion battery slurry is uniformly dispersed. By this method, over-stirring can be avoided, the battery production process time can be shortened, the battery production efficiency can be improved, and the uniformity of the lithium ion battery slurry can be effectively and accurately obtained, the evaluation period of the battery slurry can be shortened, and the reliability of the evaluation data can be enhanced.

[0041] It should be noted that the above-mentioned lithium ion battery slurry can be a positive electrode slurry or a negative electrode slurry.

[0042] Further, in some embodiments of the present application, the raw materials for preparing the positive electrode slurry include: a positive electrode active material, a conductive agent, a binder, a dispersant, and water.

[0043] Further, in some embodiments of the present application, the positive electrode active material includes at least one of lithium nickel manganese oxide, lithium iron phosphate, lithium manganese iron phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium-rich material, or lithium manganese oxide positive electrode material.

[0044] Further, in some embodiments of the present application, the conductive agent includes at least one of Super-P, KS-6, conductive carbon black, acetylene black, or CNT.

[0045] The aforementioned binder and dispersant can be selected from common binders and dispersants in the art. For example, the binder is selected from PVDF, etc.; and the dispersant is selected from CMC.

[0046] Further, in some embodiments of the present application, the raw materials for preparing the negative electrode slurry include: a negative electrode active material, a conductive agent, a binder, and water.

[0047] Further, in some embodiments of the present application, the negative active material comprises at least one of an alloy negative material, graphite, lithium titanate, silicon-carbon material, hard carbon material, or silicon-oxygen material.

[0048] Further, in some embodiments of the present application, the negative active material comprises at least one of an alloy negative material, graphite, lithium titanate, silicon-carbon material, hard carbon material, or silicon-oxygen material.

[0049] Further, in some embodiments of the present application, the conductive agent comprises at least one of Super-P, KS-6, conductive carbon black, acetylene black, or CNT.

[0050] The aforementioned binder and dispersant can be selected from common binders and dispersants in the art. For example, the binder can be SBR, etc.; and the dispersant can be CMC.

[0051] Further, in some embodiments of the present application, homogenizing comprises mixing raw materials for preparing the slurry of the lithium ion battery, and stirring.

[0052] Illustratively, the stirring of the slurry can be performed by a planetary mixer.

[0053] In other alternative embodiments of the present application, the homogenization can also be performed by other methods that can homogenize the slurry, such as vibration, etc.

[0054] Further, in some embodiments of the present application, the rate of change of the surface tension of the slurry is monitored at preset time intervals, comprising:

[0055] The surface tension values of the corresponding samples are detected at the preset time intervals, and the rate of change of the surface tension of the adjacent time interval samples is calculated.

[0056] Further, in some embodiments of the present application, the sampling at preset time intervals comprises:

[0057] The sampling is performed once every equal interval of time; optionally, the interval time is 10-90 minutes.

[0058] Further alternatively, the sampling is performed once every equal interval of time; optionally, the interval time is 15-85 minutes. Further alternatively, the interval time is 20-70 minutes. Further alternatively, the interval time is 25-65 minutes.

[0059] Illustratively, the interval time is 28 minutes, 30 minutes, 32 minutes, 35 minutes, 37 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 58 minutes, 60 minutes, 62 minutes, or 65 minutes.

[0060] Further, in some embodiments of the present application, the rate of change of surface tension of adjacent time interval samples is calculated, comprising:

[0061] According to formula (1):

[0062]

[0063] In formula (1), χ represents the rate of change of surface tension;

[0064] γ1 represents the surface tension value of the previous battery slurry;

[0065] γ2 represents the surface tension value of the next battery slurry.

[0066] It should be noted that, in order to facilitate comparative analysis, the same tank of proportioning slurry is required to have a fixed theoretical density as a surface tension calculation parameter.

[0067] Further, in order to compare the results, a flat head needle of the same specification is selected for calibration calculation.

[0068] Further, in order to compare the results, the surface tension coefficient α (which represents the mutual traction force per unit length between adjacent two parts of the suspended slurry) is selected to be within the ideal range of 0.5±0.1 recommended by the standard; when the ideal value of the liquid drop is within this range, the surface tension value can be measured and read.

[0069] In other words, during the homogenization process, the rate of change of surface tension of the slurry is monitored at a predetermined time interval, and when the rate of change of surface tension is 0.41%-0.59%, the lithium ion battery slurry is uniformly dispersed.

[0070] For example, during the homogenization process, the rate of change of surface tension of the slurry is monitored at a predetermined time interval, and when the rate of change of surface tension is 0.42%, 0.45%, 0.48%, 0.50%, 0.52%, 0.53%, 0.54%, 0.55%, 0.56%, or 0.58%, the lithium ion battery slurry is uniformly dispersed.

[0071] Further, in order to compare the results, the angle of view of the CCD lens of the contact angle tester is adjusted to 0°, and the surface tension results are measured.

[0072] Further, in order to compare the results, the titration volume of the same tank of proportioning slurry is 4-8ul, the titration rate is 2-3ml / min, and the surface tension results are measured.

[0073] According to the above analysis, in some embodiments of the present application, the surface tension value of the corresponding sample is detected, comprising:

[0074] The surface tension value of the sample is tested by using a contact angle tester.

[0075] Further, in some embodiments of the present application, the surface tension value of the sample is tested by using a contact angle tester, comprising:

[0076] The surface tension value of each sample is measured by using a pendant drop method.

[0077] Further, in some embodiments of the present application, the surface tension value of each sample is measured by using a pendant drop method, comprising:

[0078] The pendant drop is made by using a flat needle, the outer diameter of the flat needle is 0.5-2.0mm; the value of the gravitational acceleration is 9.78822, the ideal value of the drop B factor is 0.4-0.6; the titration volume is 4-8ul, the titration rate is 2-3ml / min, and the lens viewing angle is 0°.

[0079] Further optionally, the outer diameter of the flat needle is 0.6-1.9mm; further optionally, the outer diameter of the flat needle is 0.7-1.8mm.

[0080] Exemplarily, the outer diameter of the flat needle is 0.8mm, 0.9mm, 1.0mm, 1.1mm, 1.2mm, 1.3mm, 1.4mm, 1.5mm, 1.6mm or 1.7mm.

[0081] Further, in some embodiments of the present application, the ideal value of the drop B factor is 0.41-0.59.

[0082] Further optionally, in some embodiments of the present application, the ideal value of the drop B factor is 0.42-0.58.

[0083] Exemplarily, the ideal value of the drop B factor is 0.42, 0.45, 0.48, 0.50, 0.52, 0.55 or 0.57.

[0084] Further, in some embodiments of the present application, the titration volume is 4-8ul. Further optionally, in some embodiments of the present application, the titration volume is 4.5-7.5ul. Exemplarily, the titration volume is 5ul, 6ul or 7ul.

[0085] Further, in some embodiments of the present application, the titration rate is 2-3ml / min. Further optionally, in some embodiments of the present application, the titration rate is 2.1-2.9ml / min. Exemplarily, the titration rate is 2.2ml / min, 2.3ml / min, 2.4ml / min, 2.5ml / min, 2.6ml / min, 2.7ml / min or 2.8ml / min.

[0086] Some embodiments of the present application provide a method for preparing a lithium ion battery slurry, which is evaluated by the method for evaluating the uniformity of the lithium ion battery slurry provided in any of the preceding embodiments.

[0087] When the lithium ion battery slurry is evaluated to be uniformly dispersed, the total time for uniform mixing is calculated, and then the time is used as the uniform mixing time for preparing the lithium ion battery slurry.

[0088] The features and performance of the present application are further described in detail below in conjunction with the following examples:

[0089] Example 1

[0090] A method for preparing a lithium ion battery slurry is provided, which is carried out according to the following steps:

[0091] The raw materials of the negative electrode slurry are mixed, specifically including: mixing the negative electrode graphite active material: conductive agent (SP): binder SBR: CMC: ultrapure water according to the mass ratio: 93:2:2:3:10, stirring in a planetary mixer, and sampling at 0.5h, 1h, 1.5h, 2h, and 2.5h after starting stirring, respectively, to measure the surface tension of the slurry at each stirring time point. Specifically including: using a 1ml syringe to take out 1mL of slurry, a 1.0 outer diameter flat needle and calibration, titration volume 6ul, titration rate 2ml / min, gravity acceleration value: 9.78822, reading between 0.5-0.6 of the ideal value of liquid drop B factor, lens viewing angle 0°, then calculating the surface tension change rate of adjacent time intervals, the results are shown in Table 1. While measuring the surface tension, the viscosity of the slurry is measured by a viscosity tester using a rotational method, and 250mL of slurry is taken from each stage with a 4mm drill bit at a rotation speed of 20rmp. The viscosity results are shown in Table 1.

[0092] Table 1

[0093] stirring accumulation time length surface tension change rate x% viscosity value (cp) 0.5h 91.26 1598 1.0h 8.08 2894 1.5h 43.45 3072 2.0h -0.35 3102 2.5h 0.36 3089

[0094] From the test data in Table 1, it can be seen that when the stirring time is shorter, the mixed slurry is not completely mixed, and the change rate of the measured surface tension value and the viscosity value fluctuate more. After stirring for 1.5h, the slurry tends to be mixed but is not completely mixed, and the change rate of the measured surface tension value and the viscosity value are still in large fluctuation. After continuing to stir for 2.0-2.5h, the viscosity value tends to be stable, and the surface tension change rate is also the smallest, less than 0.5%. This indicates that the slurry is basically uniformly dispersed after stirring for 2h, and this result can directly guide the stirring process of the slurry. That is, when preparing the lithium ion battery negative electrode slurry subsequently, stirring for 2h, the slurry is uniformly dispersed.

[0095] Although the viscosity test results can reflect the uniformity of stirring dispersion to some extent, the viscosity test requires too much sample and causes waste of materials. Moreover, when the stirring process reaches a certain degree, the viscosity value range is wide and the accuracy is poor.

[0096] Example 2

[0097] A preparation method of lithium ion battery slurry is provided, which is carried out according to the following steps:

[0098] The raw materials of the positive electrode slurry are mixed, specifically including: mixing lithium nickel-manganese oxide positive electrode active material, conductive agent (SP), binder PVDF, CMC and ultrapure water according to the mass ratio of 92:5:1:2:20, stirring in a planetary mixer, and sampling at 0.5h, 1h, 2h, 3h and 4h after starting stirring respectively to measure the surface tension of the slurry at each stirring time point. Specifically including: taking out 1mL of the slurry with a 1ml syringe, calibrating a 1.0 outer diameter flat head needle, titrating a volume of 8ul, titrating at a rate of 3ml / min, taking the value of gravitational acceleration as 9.78822, reading the value between the ideal values of 0.4-0.5 of the liquid drop B factor, and the lens viewing angle is 0°, then calculating the surface tension change rate of adjacent time intervals, and the results are shown in Table 2. While measuring the surface tension, the viscosity of the slurry is measured by a viscosity tester by a rotation method, and 250mL of the slurry is taken at each stage to measure the viscosity at a rotation speed of 20rmp, and the results are shown in Table 2.

[0099] Table 2

[0100]

[0101]

[0102] From the test data in Table 2, when the stirring time is 0.5h-1h, the mixed slurry is not completely stirred and mixed, and the greater the fluctuation of the measured surface tension value and the viscosity value, after stirring for 2h, the slurry tends to be mixed but not completely mixed, and the measured surface tension value and the viscosity value are still in large fluctuation, and after continuous stirring for 3h-4h, the viscosity value tends to be stable, and the surface tension change rate is also the smallest, less than 0.5%, which shows that the slurry can be basically uniformly dispersed after stirring for 3h, which can directly guide the stirring process of the slurry. That is, when preparing the positive electrode slurry of the lithium ion battery, stirring for 3h, the slurry is uniformly dispersed.

[0103] Although the viscosity test results can reflect the uniformity of stirring dispersion to some extent, the viscosity test requires too much sample and causes waste of materials. Moreover, when the stirring process reaches a certain degree, the viscosity value range is wide and the accuracy is poor.

[0104] Experimental Example 1

[0105] The slurry of the positive electrode prepared in Example 2 above was uniformly coated on the surface of an aluminum foil current collector in three stages of 1.0 h, 2.0 h, and 3.0 h of stirring, and then dried in a vacuum drying oven and rolled. The positive electrode sheet had a size of 60 x 70 x 0.17.

[0106] A lithium ion battery graphite negative electrode material, a conductive agent (SP), a binder SBR, CMC, and ultrapure water were mixed in a mass ratio of 93:2:2:3:10 and stirred for 4 hours to prepare a negative electrode slurry. The slurry was uniformly coated on the surface of a copper foil current collector, dried, rolled, and cut into a negative electrode sheet having a size of 62 x 73 x 0.13.

[0107] The above positive and negative electrode sheets were separated by a 16-μm ceramic separator, stacked into an electrode core, and packaged with an aluminum plastic film. Then, 10 g of electrolyte was injected, sealed, and 3 PCS of lithium ion batteries were prepared.

[0108] After 1C charge and discharge at room temperature for 500 cycles, the battery capacity was measured. Here, the specific capacity was calculated by the formula: specific capacity = 1C capacity of the battery / mass of the active material. The results are shown in Table 3.

[0109] Table 3

[0110]

[0111] From the comparison and analysis of the test results in Table 3, it can be seen that the battery prepared by stirring the positive electrode slurry for 3 h has the best performance, followed by the battery prepared by stirring for 2 h, and the battery prepared by stirring for 1 h has the worst performance. This is consistent with the results of Example 1 and Example 2. It is shown that the method of the present application can more accurately evaluate and guide the slurry stirring process.

[0112] In summary, the method of the present application can more accurately and quickly evaluate the dispersion degree of the battery slurry, thereby timely guiding the improvement of the production slurry preparation process and avoiding the great cost waste caused by problems in the production of the slurry.

[0113] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for evaluating the homogeneity of a lithium-ion battery slurry, characterized in that, The application relates to a method for evaluating the uniformity of lithium ion battery slurry. During homogenization, samples are taken at preset time intervals, surface tension values of the corresponding samples are detected, and the surface tension change rate of adjacent time interval samples is calculated, if the surface tension change rate is within the range corresponding to the preset time interval, the lithium ion battery slurry is uniformly dispersed. The calculation of the surface tension change rate of adjacent time interval samples comprises: The surface tension change rate is calculated according to formula (1): In formula (1), χ represents the surface tension change rate; γ1 represents the surface tension value of the previous battery slurry; γ2 represents the surface tension value of the next battery slurry.

2. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 1, wherein, The sampling at preset time intervals comprises: Sampling once every equal interval of time.

3. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 2, characterized in that, The interval time is 10-90 minutes.

4. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 1, wherein, The detection of the surface tension value of the corresponding sample comprises: The surface tension value of the sample is detected by using a contact angle tester.

5. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 4, wherein, The detection of the surface tension value of the sample by using the contact angle tester comprises: The surface tension value of each sample is measured by using the pendant drop method.

6. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 5, wherein, The surface tension value of each sample is measured by using the pendant drop method, wherein the outer diameter of the flat needle is 0.5-2.0 mm, the value of the gravitational acceleration is 9.78822, the ideal value of the droplet B factor is 0.4-0.6, the titration volume is 4-8 ul, the titration rate is 2-3 ml / min, and the lens viewing angle is 0°. The homogenization comprises:

7. The method for evaluating the homogeneity of the slurry of a lithium-ion battery according to any one of claims 1 to 6, characterized in that, Mixing raw materials for preparing lithium ion battery slurry and stirring. The raw materials for preparing lithium ion battery slurry comprise: positive active material, conductive agent, binder, dispersant, water; or negative active material, conductive agent, binder, water.

8. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 7, wherein, The positive active material comprises at least one of lithium nickel manganese acid, lithium iron phosphate, lithium manganese iron phosphate, nickel cobalt manganese ternary material, nickel cobalt aluminum ternary material, lithium-rich material or lithium manganese acid positive material.

9. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 8, wherein, The negative active material comprises at least one of alloy negative material, graphite, lithium titanate, silicon-carbon material, hard carbon material or silicon-oxygen material.

10. The method of evaluating the homogeneity of a lithium-ion battery slurry according to claim 8, wherein, The conductive agent comprises at least one of Super-P, KS-6, conductive carbon black, acetylene black or CNT.

11. The method of evaluating the homogeneity of a lithium-ion battery slurry of claim 8, wherein, The solid content ratio of the lithium ion battery slurry is 50%-90%.

12. The method of evaluating the homogeneity of a lithium-ion battery slurry according to any one of claims 1 to 6, characterized in that, The lithium ion battery slurry uniformity evaluation method is used for evaluation.

13. A method of preparing a lithium ion battery slurry, characterized by, When the lithium ion battery slurry is uniformly dispersed, the total time for uniform material is calculated, and then the time is used as the uniform material time for preparing the lithium ion battery slurry. ​

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