Evaluation method for dispersing performance of lithium ion battery slurry

Abstract

The invention relates to the field of new energy batteries, in particular to a lithium ion battery slurry dispersing performance evaluation method which comprises the following steps: S1, performing first stirring treatment on lithium ion battery slurry to obtain a first material; s2, carrying out at least three times of performance tests on the first material; s3, judging the dispersing performance of the lithium ion battery slurry according to the change rate of the performance test; wherein the performance test comprises at least one of fineness test, viscosity test and potential test; a second stirring treatment is carried out between two adjacent performance tests. The evaluation method disclosed by the invention can be quantized, has good repeatability and reproducibility, can be used for judging the dispersity of the key material in a short time at low cost, and is simple to operate and high in practical value.

Description

Technical Field

[0001] The present invention relates to the field of new energy batteries, and in particular to a method for evaluating the dispersion performance of lithium-ion battery slurry. Background Art

[0002] Currently, the lithium-ion industry widely uses small particle materials and dispersants such as lithium iron phosphate, lithium iron manganese phosphate, and carbon black, which can present dispersion issues during mass production. Lithium-ion secondary batteries are often connected in series and parallel to meet the voltage and current requirements of the equipment being used. Poor battery consistency can easily lead to reverse charging between series-connected cells—reverse charging of the battery. The negative electrode copper foil dissolves and gradually deposits on the positive electrode, causing the internal resistance of the charged battery to gradually increase and resulting in severe heat generation. Overheating can easily lead to fire and explosion, posing a significant risk. Therefore, battery consistency is a key indicator of battery performance. The primary factor affecting battery consistency is poor slurry dispersion due to the high volume of raw materials and production processes. There is an urgent need for faster and more effective identification of dispersion risks. Simultaneously, effective and rapid methods are needed to identify materials with dispersion risks and the effectiveness of dispersants. This can reduce costs, improve development efficiency, and mitigate mass production risks. Summary of the Invention

[0003] In view of this, the present invention is dedicated to providing a method for evaluating the dispersion performance of lithium-ion battery slurry to solve the problem in the prior art that the dispersion risk of battery slurry cannot be quickly and effectively identified.

[0004] In order to solve the above-mentioned technical problems, the present invention is achieved as follows:

[0005] The present invention provides a method for evaluating the dispersion performance of lithium-ion battery slurry, the evaluation method comprising the following steps:

[0006] S1. performing a first stirring process on the lithium-ion battery slurry to obtain a first material;

[0007] S2. Perform at least three performance tests on the first material;

[0008] S3. Determining the dispersion performance of the lithium-ion battery slurry according to the change rate of the performance test;

[0009] The performance test includes at least one of a fineness test, a viscosity test and a potential test; and a second stirring process is included between two adjacent performance tests.

[0010] Optionally, the conditions for the first stirring treatment include: stirring time of 40 to 60 minutes, stirring speed of 1800 to 2200 r / min; the conditions for the second stirring treatment include: stirring time of 10 to 30 minutes, stirring speed of 1800 to 2200 r / min; and the performance test is performed 4 to 6 times.

[0011] Optionally, the step of calculating the rate of change of the fineness test includes: calculating the difference in fineness between two adjacent fineness tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent fineness tests; and calculating the ratio of the fineness difference to the time difference to obtain the rate of change of the fineness test; wherein the time interval is measured in minutes and the fineness is measured in μm. If the rate of change of the fineness test is greater than -0.3 μm / min, it indicates that the dispersion performance of the lithium-ion battery slurry is poor; if the rate of change of the fineness test is less than -0.35 μm / min, it indicates that the dispersion performance of the lithium-ion battery slurry is good. Optionally, the fineness test is performed using a scraper fineness meter.

[0012] Optionally, the step of calculating the rate of change of the viscosity test includes: calculating the viscosity difference between two adjacent viscosity tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent viscosity tests; calculating the ratio of the viscosity difference to the time difference to obtain the rate of change of the viscosity test; wherein the time interval is measured in minutes and the viscosity is measured in mPa.S; if the rate of change of the viscosity test is less than -150mPa.S / min, it indicates that the dispersion performance of the lithium-ion battery slurry is good; if the rate of change of the viscosity test is greater than -100mPa.S / min, it indicates that the dispersion performance of the lithium-ion battery slurry is poor.

[0013] Optionally, the viscosity test is performed using a viscosity tester; optionally, the viscosity tester has a viscosity range of 0.5 to 100,000 mPa·s, a rotation speed of 10 to 30 rpm, and a temperature range of 20 to 120°C.

[0014] Optionally, the step of calculating the rate of change of the potential test includes: calculating the potential difference between two adjacent potential tests of the lithium-ion battery slurry; calculating the time difference between two adjacent potential tests; calculating the ratio of the potential difference to the time difference to obtain the rate of change of the potential test, wherein the time interval is measured in minutes and the potential is measured in mV; if the rate of change of the potential test is less than 0.3mV / min, it indicates that the dispersion performance of the lithium-ion battery slurry is poor; if the rate of change of the potential test is greater than 0.32mV / min, it indicates that the dispersion performance of the lithium-ion battery slurry is good.

[0015] Optionally, the potential test is performed using a Zeta potential analyzer; optionally, the Zeta potential range of the Zeta potential analyzer is -150 to 150 mV, the particle size range is 10 nm to 30 μm, the conductivity range is 0 to 200 ms / cm, the test angle is 90 degrees, and the temperature range is 2 to 90°C.

[0016] Optionally, the lithium-ion battery slurry is a positive electrode slurry; optionally, the positive electrode slurry includes a positive electrode active material, a positive electrode binder, a positive electrode dispersant and a positive electrode solvent; optionally, the solid content of the positive electrode slurry is 40-70%, preferably 50-60%; optionally, the mass ratio of the positive electrode active material, the positive electrode binder, the positive electrode dispersant and the positive electrode solvent is (48.3-51.2): (0.7-1.3): (0.1-0.4): (48-50).

[0017] Optionally, the lithium-ion battery slurry is a negative electrode slurry; optionally, the negative electrode slurry includes a negative electrode active material, a negative electrode binder, a negative electrode thickener and a negative electrode solvent; optionally, the solid content of the negative electrode slurry is 40-70%, preferably 50-60%; optionally, the mass ratio of the negative electrode active material, the negative electrode binder, the negative electrode thickener and the negative electrode solvent is (1.4-1.6): (0.7-0.9): (1.4-1.6): (95.9-96.5).

[0018] Through the above technical solution, the present invention provides a method for evaluating the dispersion performance of lithium-ion battery slurry, comprising: subjecting the lithium-ion battery slurry to a first stirring process to obtain a first material; performing at least three performance tests on the first material; and determining the dispersion performance of the lithium-ion battery slurry based on the rate of change of the performance tests. This method is quantitative and has good repeatability and reproducibility. It can quickly and cost-effectively determine the dispersion performance of key materials, is simple to operate, and has high practical value.

[0019] Other features and advantages of the present invention will be described in detail in the following detailed description. DETAILED DESCRIPTION

[0020] The present invention discloses a method for evaluating the dispersion performance of lithium-ion battery slurry. Those skilled in the art can refer to the content of this article and appropriately improve the process parameters to achieve the desired results. It should be noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in the present invention. The methods and applications of the present invention have been described through preferred embodiments. It is obvious that relevant personnel can modify or appropriately change and combine the methods and applications described herein without departing from the content, spirit and scope of the present invention to implement and apply the technology of the present invention.

[0021] In the description of the present invention, a list of items connected by the term "at least one of" or other similar terms can mean any combination of the listed items. For example, if items A and B are listed, the phrase "at least one of A and B" means only A; only B; or A and B. In another example, if items A, B, and C are listed, the phrase "at least one of A, B, and C" means only A; or only B; only C; A and B (excluding C); A and C (excluding B); B and C (excluding A); or all of A, B, and C. Item A can include a single element or multiple elements. Item B can include a single element or multiple elements. Item C can include a single element or multiple elements.

[0022] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range or the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0023] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0024] Unless otherwise specified, all technical features and optional technical features of the present invention can be combined with each other to form a new technical solution.

[0025] Unless otherwise specified, the terms "include" and "comprising" used in the present invention may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0026] Lithium-ion secondary batteries are often connected in series and parallel to meet the voltage and current requirements of the devices they are used in. Poor battery consistency can easily lead to reverse charging between series-connected batteries—a phenomenon in which a battery is reversely charged. This can cause the negative electrode copper foil to dissolve and gradually deposit onto the positive electrode, gradually increasing the internal resistance of the charged battery and causing significant heat generation. Overheating can easily lead to fire and explosion, posing a significant risk. Therefore, battery consistency is a key indicator of battery performance. The primary factor affecting battery consistency is poor slurry dispersion due to the high volume of raw materials and production processes, necessitating faster and more effective identification of dispersion risks.

[0027] In order to solve the problem in the prior art that the dispersion risk of battery slurry cannot be quickly and effectively identified, the present invention adopts the following technical solutions:

[0028] The present invention provides a method for evaluating the dispersion performance of lithium-ion battery slurry, the evaluation method comprising the following steps:

[0029] S1. performing a first stirring process on the lithium-ion battery slurry to obtain a first material;

[0030] S2. Perform at least three performance tests on the first material;

[0031] S3. Determining the dispersion performance of the lithium-ion battery slurry according to the change rate of the performance test;

[0032] The performance test includes at least one of a fineness test, a viscosity test and a potential test; and a second stirring process is included between two adjacent performance tests.

[0033] The evaluation method of the lithium-ion battery slurry dispersion performance of the present invention can be quantified and has good repeatability and reproducibility, can determine the dispersion of key materials in a short time and at low cost, is simple to operate, and has high practical value.

[0034] In a specific embodiment of the present invention, a small stirring tank can be used to prepare a slurry of about 50 mL. After stirring at a certain speed for a certain period of time, the changes in fineness, viscosity, and Zeta potential over time are detected, and the dispersibility is determined by the rate of change.

[0035] According to the present invention, the conditions for the first stirring treatment may include: a stirring time of 40 to 60 minutes, and a stirring speed of 1800 to 2200 r / min. Among them, if the stirring time of the first stirring treatment is too long, it may cause the instrument to overheat and shorten its life, thereby reducing the efficiency of the experiment; if the stirring time is too short, it may result in insufficient stirring and failure to achieve preliminary dispersion; due to the limited capacity of the instrument, an excessively large speed may cause the instrument to malfunction and reduce its service life; if the stirring speed is too low, it may result in insufficient stirring. As an example, the stirring time of the first stirring treatment may be 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, etc., and the stirring speed of the first stirring treatment may be 1800 r / min, 1900 r / min, 2000 r / min, 2100 r / min, 2200 r / min, etc.

[0036] According to the present invention, the conditions for the second stirring treatment may include: a stirring time of 10 to 30 minutes, and a stirring speed of 1800 to 2200 r / min. Among them, if the stirring time of the second stirring treatment is too long, it may cause the instrument to overheat and shorten its life, thereby reducing the efficiency of the experiment; if the stirring time is too short, it may result in insufficient stirring and failure to achieve preliminary dispersion; due to the limited capacity of the instrument, excessive speed may cause the instrument to malfunction and reduce its service life; if the stirring speed is too low, it may result in insufficient stirring. As an example, the stirring time of the second stirring treatment may be 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc., and the stirring speed of the second stirring treatment may be 1800 r / min, 1900 r / min, 2000 r / min, 2100 r / min, 2200 r / min, etc.

[0037] According to the present invention, in order to facilitate the determination of the rate of change of the performance test and to save experimental costs, the performance test is preferably performed 4 to 6 times. In a specific embodiment, stirring can be performed at a speed of 1800-2200 r / min for 40 to 60 minutes, and then stirring can be continued, but the fineness, viscosity, and potential are recorded every 10 to 30 minutes.

[0038] In one embodiment of the present invention, the step of calculating the rate of change of the fineness test may include:

[0039] Calculating the fineness difference between two adjacent fineness tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent fineness tests; calculating the ratio of the fineness difference to the time difference to obtain the change rate of the fineness test;

[0040] Among them, the time interval is measured in minutes, and the fineness is measured in μm. If the change rate of the fineness test is greater than -0.3 μm / min, it means that the dispersion performance of the lithium-ion battery slurry is poor; if the change rate of the fineness test is less than -0.35 μm / min, it means that the dispersion performance of the lithium-ion battery slurry is good.

[0041] As an example, the fineness test is performed using a scraper fineness meter.

[0042] Exemplarily, the scraper testing method can be: wipe the scraper fineness meter (range 0-100μm) and the scraper surface with dust-free paper soaked in alcohol. Place the wiped scraper fineness meter and scraper on a flat table. Use a spoon to take a small spoonful of the slurry to be tested and drip 2-3 drops into the deepest part of the groove at the top of the fineness meter. Hold the scraper with both hands, with the blade at the top of the scraper fineness meter and perpendicular to the surface of the fineness meter, and make good contact between the scraper blade and the surface of the scraper fineness meter. Pull the scraper to the minimum scale value within 3 seconds to fill the groove with the slurry. After the scraper is pulled, make the line of sight at an angle of 15-30° to the groove plane, observe the starting point of the particle scratch in the groove against the light, record the value of μm at the scratch in the cathode stirring process record sheet, and read the reading accurately to the minimum scale value, and observe whether there are bubbles.

[0043] In this embodiment, the slurry contacts and moves with the scraper fineness meter, causing the sample to be subjected to shear force, thereby separating the particles and arranging them on the scraper to form a particle layer. The fineness data corresponding to the fineness plate is recorded at the starting point of the scratch, and the dispersibility is determined by the starting point. The smaller the fineness, the better the dispersibility.

[0044] In one embodiment of the present invention, the step of calculating the rate of change of the viscosity test may include:

[0045] Calculating the viscosity difference between two adjacent viscosity tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent viscosity tests; calculating the ratio of the viscosity difference to the time difference to obtain the rate of change of the viscosity test;

[0046] Wherein, the time interval is measured in minutes, and the viscosity is measured in mPa.S; if the rate of change of the viscosity test is less than -150 mPa.S / min, it indicates that the dispersion performance of the lithium-ion battery slurry is good; if the rate of change of the viscosity test is greater than -100 mPa.S / min, it indicates that the dispersion performance of the lithium-ion battery slurry is poor.

[0047] As an example, the viscosity test may be performed using a viscosity tester; optionally, the viscosity tester may have a viscosity range of 0.5 to 100,000 mPa·s, a rotation speed of 10 to 30 rpm, and a temperature range of 20 to 120°C.

[0048] Exemplarily, the test method for testing using a viscosity tester can be: on the touch screen interface of the viscosity tester, click on the viscosity test to enter the viscosity test setting interface, and set the rotor (rotor No. 5) and speed parameters (20rap speed) corresponding to the slurry to be tested according to the stirring instruction sheet, and the temperature is 25 degrees. According to the requirements of the stirring instruction sheet, select the rotor model that meets the requirements for installation, clean the beaker and the rotor to be used, use the beaker to take about 500mL of slurry, and place it directly under the instrument. Use the instrument torsion bar to adjust the height of the instrument to a position where the rotor can be installed and install the rotor. Adjust the height of the viscometer so that the rotor is immersed in the slurry to be tested. Click "Run" on the touch screen to start the test. Read the viscosity value on the "Result Table" on the display screen.

[0049] In this embodiment, the interaction between the solid particles in the slurry causes the fluid's viscosity to increase. As the slurry flows, friction between the particles creates resistance, which can be characterized by viscosity. The greater the rate of change in viscosity, the higher the viscosity of the fluid, the greater the resistance to flow, and the poorer the slurry's dispersibility.

[0050] In one embodiment of the present invention, the step of calculating the rate of change of the potential test may include:

[0051] Calculating the potential difference between two adjacent potential tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent potential tests; calculating the ratio of the potential difference to the time difference to obtain the rate of change of the potential test;

[0052] Among them, the time interval is measured in minutes and the potential is measured in mV; if the rate of change of the potential test is less than 0.3mV / min, it means that the dispersion performance of the lithium-ion battery slurry is poor; if the rate of change of the potential test is greater than 0.32mV / min, it means that the dispersion performance of the lithium-ion battery slurry is good.

[0053] As an example, the potential test can be performed using a Zeta potential analyzer; optionally, the Zeta potential range of the Zeta potential analyzer can be -150 to 150 mV, the particle size range can be 10 nm to 30 μm, the conductivity range can be 0 to 200 ms / cm, the test angle can be 90 degrees, and the temperature range can be 2 to 90°C.

[0054] For example, the test method using a Zeta potential analyzer can be: inject the sample into a dedicated electrode tank, apply an appropriate voltage (usually 50-150V) to avoid excessive voltage causing heating or electrolysis, and the instrument analyzes the particle mobility through laser Doppler velocimetry and automatically calculates the Zeta potential.

[0055] In this embodiment, solid particles in the slurry are dispersed into the liquid medium. The particles carry a net charge on their surface, attracting an equal amount of oppositely charged particles. The potential of the sliding surface at the interface between the compact layer and the diffuse layer is the zeta potential. A larger absolute value of the rate of change of the zeta potential indicates a more stable dispersion, with a greater tendency for electrostatic repulsion between particles to agglomerate. Conversely, a smaller absolute value of the rate of change of the zeta potential indicates a more stable dispersion, with a greater tendency for van der Waals attraction between particles to agglomerate.

[0056] As an exemplary embodiment of the present invention, the lithium-ion battery slurry may be a positive electrode slurry; optionally, the positive electrode slurry includes a positive electrode active material, a positive electrode binder, a positive electrode dispersant, and a positive electrode solvent. In this embodiment, the solid content of the positive electrode slurry may be 40-70%, preferably 50-60%; optionally, the mass ratio of the positive electrode active material, the positive electrode binder, the positive electrode dispersant, and the positive electrode solvent may be (48.3-51.2):(0.7-1.3):(0.1-0.4):(48-50).

[0057] Illustratively, the positive electrode active material in the present invention may include at least one of lithium iron phosphate, lithium manganese iron phosphate, manganese oxide, nickel cobalt aluminum ternary material, nickel cobalt manganese ternary material, lithium-rich material, sodium electric layer oxygen material and sodium electric polyanion positive electrode material; the positive electrode binder in the present invention may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylic acid (PAA) and polyvinyl alcohol (PVA); the positive electrode dispersant in the present invention may include at least one of polyvinyl pyrrolidone (PVP), polyethylene glycol (PEG), sodium dodecyl sulfate (SDS), sodium dodecylbenzene sulfonate (SDBS) and non-ionic Tween series (such as Tween-80); the positive electrode solvent in the present invention may be water and / or N-methylpyrrolidone.

[0058] As another exemplary embodiment of the present invention, the lithium-ion battery slurry may be a negative electrode slurry; optionally, the negative electrode slurry includes a negative electrode active material, a negative electrode binder, a negative electrode thickener, and a negative electrode solvent. In this embodiment, the solid content of the negative electrode slurry is 40-70%, preferably 50-60%. Optionally, the mass ratio of the negative electrode active material, the negative electrode binder, the negative electrode thickener, and the negative electrode solvent is (1.4-1.6):(0.7-0.9):(1.4-1.6):(95.9-96.5).

[0059] Illustratively, the negative electrode active material in the present invention may include at least one of graphite, lithium titanate, silicon oxide material, and alloy negative electrode material; the negative electrode binder in the present invention may include at least one of polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), styrene-butadiene rubber (SBR), polyacrylic acid (PAA) and polyvinyl alcohol (PVA); the negative electrode thickener in the present invention may include at least one of sodium carboxymethyl cellulose (CMC), hydroxyethyl cellulose (HEC), sodium polyacrylate (Na-PAA), polyvinyl alcohol (PVA) and xanthan gum; the negative electrode solvent in the present invention may be water.

[0060] The present invention is further described in detail below by way of examples. The raw materials used in the examples can all be obtained through commercial sources.

[0061] Example 1

[0062] In this example, positive electrode slurry 1 was used as the slurry to be tested. Positive electrode slurry 1 had a solids content of 50% and included a positive electrode active material, a positive electrode binder, a positive electrode dispersant, and a positive electrode solvent. The positive electrode active material was lithium iron phosphate, the positive electrode binder was PVDF, the positive electrode dispersant was a high molecular weight polyethylene glycol (degree of polymerization n=120), and the positive electrode solvent was NMP. The mass ratio of the positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent was 48.9:1.0:0.1:50.

[0063] (1) Fineness test

[0064] The positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent were mixed according to the recipe and subjected to a first stirring process to obtain a first material. The fineness of the first material was tested using a scraper fineness meter. The first stirring process lasted for 60 minutes at a speed of 2000 r / min. The first material was stirred continuously at 2000 r / min, and the fineness was tested every 20 minutes. This test was repeated six times.

[0065] Among them, the scraper fineness meter test method includes: wiping the scraper fineness meter (range 0-100μm) and the scraper surface with dust-free paper soaked in alcohol. Place the wiped scraper fineness meter and scraper on a flat table. Use a spoon to take a small spoonful of the first material and drip 3 drops into the deepest part of the groove at the top of the fineness meter. Hold the scraper with both hands, with the blade at the top of the scraper fineness meter and perpendicular to the surface of the fineness meter, and make good contact between the scraper blade and the surface of the scraper fineness meter. Pull the scraper to the minimum scale value within 3 seconds to fill the groove with the slurry. After the scraper is pulled, make the line of sight at an angle of 15-30° to the groove plane, observe the starting point of the particle scratch in the groove against the light, record the value of μm at the scratch in the cathode stirring process record sheet, and read the reading accurately to the minimum scale value, and observe whether there are bubbles.

[0066] The test results of the fineness test of the positive electrode slurry 1 in this embodiment 1 are shown in Table 1, and the fineness change rate is shown in Table 2. The calculation method of the fineness change rate is: (the fineness at the end point within the time period - the fineness at the initial point within the time period) / the specific time of the time period, where the time is measured in minutes.

[0067] (2) Viscosity test

[0068] The positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent were mixed according to the recipe and subjected to a first stirring process to obtain a first material. The viscosity of the first material was tested using a viscosity tester. The first stirring process lasted for 60 minutes at a speed of 2000 r / min. The first material was stirred continuously at 2000 r / min, and the viscosity was tested every 20 minutes. This test was repeated six times.

[0069] Among them, the viscosity tester test method includes: on the touch screen interface of the viscosity tester, click on the viscosity test to enter the viscosity test setting interface, and set the rotor (rotor No. 5) and speed parameters (20rap speed) corresponding to the slurry to be tested according to the stirring instruction sheet, and the temperature is 25 degrees. According to the requirements of the stirring instruction sheet, select the rotor model that meets the requirements for installation, clean the beaker and the rotor to be used, use the beaker to take about 500mL of slurry, and place it directly under the instrument. Use the instrument torsion bar to adjust the height of the instrument to the position where the rotor can be installed and install the rotor. Adjust the height of the viscometer so that the rotor is immersed in the slurry to be tested. Click "Run" on the touch screen to start the test. Read the viscosity value on the "Result Table" on the display screen.

[0070] The test results of the viscosity test of the positive electrode slurry 1 in this embodiment 1 are shown in Table 3, and the viscosity change rate is shown in Table 4. The viscosity change rate is calculated as follows: (end point viscosity within the time period - initial point viscosity within the time period) / specific time of the time period, where the time is measured in minutes.

[0071] (3) Potential test

[0072] The positive electrode active material, positive electrode binder, positive electrode dispersant and positive electrode solvent are mixed according to the formula, and a first stirring process is performed to obtain a first material. The Zeta potential of the first material is tested using a Zeta potential analyzer. The first stirring process lasts for 60 minutes and the first stirring process speed is 2000 r / min. The first material is continued to be stirred at a speed of 2000 r / min, and the Zeta potential is tested every 20 minutes. The test is repeated six times.

[0073] Among them, the Zeta potential analyzer testing method includes: injecting the sample into a dedicated electrode slot, applying a voltage of 100V, and the instrument analyzes the particle mobility through laser Doppler velocimetry and automatically calculates the Zeta potential.

[0074] The test results of the potential test of the positive electrode slurry 1 in this embodiment 1 are shown in Table 5, and the potential change rate is shown in Table 6. The potential change rate is calculated as follows: (end point potential within the time period - initial point potential within the time period) / specific time of the time period, where time is measured in minutes.

[0075] Example 2

[0076] In this example, positive electrode slurry 2 was used as the slurry to be tested. Positive electrode slurry 1 had a solids content of 50% and included a positive electrode active material, a positive electrode binder, a positive electrode dispersant, and a positive electrode solvent. The positive electrode active material was lithium iron phosphate, the positive electrode binder was PVDF, the positive electrode dispersant was high molecular weight sodium polyacrylate (degree of polymerization n=110), and the positive electrode solvent was NMP. The mass ratio of the positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent was 48.9:1.0:0.1:50.

[0077] (1) Fineness test

[0078] The method for fineness testing in this embodiment is the same as that in Example 1. The test results of the fineness test of the positive electrode slurry 2 in this embodiment are shown in Table 1, and the fineness change rate is shown in Table 2.

[0079] (2) Viscosity test

[0080] The viscosity test method in this embodiment is the same as that in Example 1. The test results of the viscosity test of the positive electrode slurry 2 in this embodiment are shown in Table 3, and the viscosity change rate is shown in Table 4.

[0081] (3) Potential test

[0082] The method for potential testing in this embodiment is the same as that in Example 1. The test results of the potential test of positive electrode slurry 2 in this embodiment are shown in Table 5, and the potential change rate is shown in Table 6.

[0083] Example 3

[0084] In this example, positive electrode slurry 3 was used as the slurry to be tested. Positive electrode slurry 1 had a solids content of 50% and included a positive electrode active material, a positive electrode binder, a positive electrode dispersant, and a positive electrode solvent. The positive electrode active material was lithium iron phosphate, the positive electrode binder was PVDF, the positive electrode dispersant was a relatively high molecular weight polyethylene glycol (degree of polymerization n=50), and the positive electrode solvent was NMP. The mass ratio of the positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent was 48.9:1.0:0.1:50.

[0085] (1) Fineness test

[0086] The method for fineness testing in this embodiment is the same as that in Example 1. The test results of the fineness test of the positive electrode slurry 3 in this embodiment are shown in Table 1, and the fineness change rate is shown in Table 2.

[0087] (2) Viscosity test

[0088] The viscosity test method in this embodiment is the same as that in Example 1. The test results of the viscosity test of the positive electrode slurry 3 in this embodiment are shown in Table 3, and the viscosity change rate is shown in Table 4.

[0089] (3) Potential test

[0090] The method for potential testing in this embodiment is the same as that in Example 1. The test results of the potential test of positive electrode slurry 3 in this embodiment are shown in Table 5, and the potential change rate is shown in Table 6.

[0091] Example 4

[0092] In this example, positive electrode slurry 4 was used as the slurry to be tested. Positive electrode slurry 1 had a solids content of 50% and included a positive electrode active material, a positive electrode binder, a positive electrode dispersant, and a positive electrode solvent. The positive electrode active material was lithium iron phosphate, the positive electrode binder was PVDF, the positive electrode dispersant was a relatively high molecular weight sodium polyacrylate (degree of polymerization n=49), and the positive electrode solvent was NMP. The mass ratio of the positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent was 48.9:1.0:0.1:50.

[0093] (1) Fineness test

[0094] The method for fineness testing in this embodiment is the same as that in Example 1. The test results of the fineness test of the positive electrode slurry 4 in this embodiment are shown in Table 1, and the fineness change rate is shown in Table 2.

[0095] (2) Viscosity test

[0096] The viscosity test method in this embodiment is the same as that in Example 1. The test results of the viscosity test of the positive electrode slurry 4 in this embodiment are shown in Table 3, and the viscosity change rate is shown in Table 4.

[0097] (3) Potential test

[0098] The method for potential testing in this embodiment is the same as that in Example 1. The test results of the potential test of positive electrode slurry 4 in this embodiment are shown in Table 5, and the potential change rate is shown in Table 6.

[0099] Example 5

[0100] In this example, positive electrode slurry 5 was used as the slurry to be tested. Positive electrode slurry 1 had a solids content of 50% and included a positive electrode active material, a positive electrode binder, a positive electrode dispersant, and a positive electrode solvent. The positive electrode active material was lithium iron phosphate, the positive electrode binder was PVDF, the positive electrode dispersant was a low molecular weight polyethylene glycol (degree of polymerization n=9), and the positive electrode solvent was NMP. The mass ratio of the positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent was 48.9:1.0:0.1:50.

[0101] (1) Fineness test

[0102] The method for fineness testing in this embodiment is the same as that in Example 1. The test results of the fineness test of the positive electrode slurry 5 in this embodiment are shown in Table 1, and the fineness change rate is shown in Table 2.

[0103] (2) Viscosity test

[0104] The viscosity test method in this embodiment is the same as that in Example 1. The test results of the viscosity test of the positive electrode slurry 5 in this embodiment are shown in Table 3, and the viscosity change rate is shown in Table 4.

[0105] (3) Potential test

[0106] The method for potential testing in this embodiment is the same as that in Example 1. The test results of the potential test of the positive electrode slurry 5 in this embodiment are shown in Table 5, and the potential change rate is shown in Table 6.

[0107] Example 6

[0108] In this example, positive electrode slurry 6 was used as the slurry to be tested. Positive electrode slurry 1 had a solids content of 50% and included a positive electrode active material, a positive electrode binder, a positive electrode dispersant, and a positive electrode solvent. The positive electrode active material was lithium iron phosphate, the positive electrode binder was PVDF, the positive electrode dispersant was a low molecular weight polyethylene glycol (degree of polymerization n=8), and the positive electrode solvent was NMP. The mass ratio of the positive electrode active material, positive electrode binder, positive electrode dispersant, and positive electrode solvent was 48.9:1.0:0.1:50.

[0109] (1) Fineness test

[0110] The method for fineness testing in this embodiment is the same as that in Example 1. The test results of the fineness test of the positive electrode slurry 6 in this embodiment are shown in Table 1, and the fineness change rate is shown in Table 2.

[0111] (2) Viscosity test

[0112] The viscosity test method in this embodiment is the same as that in Example 1. The test results of the viscosity test of the positive electrode slurry 6 in this embodiment are shown in Table 3, and the viscosity change rate is shown in Table 4.

[0113] (3) Potential test

[0114] The method for potential testing in this embodiment is the same as that in Example 1. The test results of the potential test of the positive electrode slurry 6 in this embodiment are shown in Table 5, and the potential change rate is shown in Table 6.

[0115] Table 1 Fineness test results

[0116]

[0117] Table 2 Calculation results of fineness test change rate (the unit of fineness change rate is μm / min)

[0118]

[0119] Table 3 Viscosity test results

[0120]

[0121] Table 4 Calculation results of viscosity test change rate (the unit of viscosity change rate is mPa.S / min)

[0122]

[0123] Table 5 Potential test results

[0124]

[0125] Table 6 Calculation results of potential test change rate (unit of potential change rate is mV / min)

[0126]

[0127] It can be seen from Tables 1 and 2 that the rate of change of the fineness test of positive electrode slurry 1 and positive electrode slurry 2 is less than -0.35μm / min, that is, positive electrode slurry 1 and positive electrode slurry 2 have good dispersion performance; the rate of change of the fineness test of positive electrode slurry 3 and positive electrode slurry 4 is between -0.3 and -0.35μm / min, that is, compared with positive electrode slurry 1 and positive electrode slurry 2, positive electrode slurry 3 and positive electrode slurry 4 have poor dispersion performance; the rate of change of the fineness test of positive electrode slurry 5 and positive electrode slurry 6 is generally greater than -0.3μm / min, that is, positive electrode slurry 5 and positive electrode slurry 6 have the worst dispersion performance.

[0128] It can be seen from Tables 3 and 4 that the rate of change of the viscosity test of positive electrode slurry 1 and positive electrode slurry 2 is less than -150 mPa.S / min, that is, positive electrode slurry 1 and positive electrode slurry 2 have good dispersion performance; the rate of change of the viscosity test of positive electrode slurry 3 and positive electrode slurry 4 is between -100 and -150 mPa.S / min, that is, compared with positive electrode slurry 1 and positive electrode slurry 2, positive electrode slurry 3 and positive electrode slurry 4 have poor dispersion performance; the rate of change of the viscosity test of positive electrode slurry 5 and positive electrode slurry 6 is generally greater than -100 mPa.S / min, that is, positive electrode slurry 5 and positive electrode slurry 6 have the worst dispersion performance.

[0129] It can be seen from Tables 5 and 6 that the rate of change of the potential test of positive electrode slurry 1 and positive electrode slurry 2 is greater than 0.32mV / min, that is, positive electrode slurry 1 and positive electrode slurry 2 have good dispersion performance; the rate of change of the potential test of positive electrode slurry 3 and positive electrode slurry 4 is between 0.3 and 0.4mV / min, that is, compared with positive electrode slurry 1 and positive electrode slurry 2, positive electrode slurry 3 and positive electrode slurry 4 have poor dispersion performance; the rate of change of the potential test of positive electrode slurry 5 and positive electrode slurry 6 is less than 0.3mV / min, that is, positive electrode slurry 5 and positive electrode slurry 6 have the worst dispersion performance.

[0130] Therefore, each positive electrode slurry in the embodiment was subjected to fineness test, viscosity test and potential test respectively, and the conclusions obtained were consistent, that is, the method of the present invention is accurate in testing and has good repeatability and reproducibility.

[0131] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A method for evaluating the dispersion performance of lithium-ion battery slurry, characterized in that: The evaluation method comprises the following steps: S1. performing a first stirring process on the lithium-ion battery slurry to obtain a first material; S2. Perform at least three performance tests on the first material; S3. Determining the dispersion performance of the lithium-ion battery slurry according to the change rate of the performance test; The performance test includes at least one of a fineness test, a viscosity test and a potential test; and a second stirring process is included between two adjacent performance tests.

2. The evaluation method according to claim 1, wherein: The conditions of the first stirring treatment include: a stirring time of 40 to 60 minutes and a stirring speed of 1800 to 2200 r / min; The conditions of the second stirring treatment include: a stirring time of 10 to 30 minutes and a stirring speed of 1800 to 2200 r / min; The performance test was performed 4 to 6 times.

3. The evaluation method according to claim 1, wherein: The calculation step of the rate of change of the fineness test includes: Calculating the fineness difference between two adjacent fineness tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent fineness tests; calculating the ratio of the fineness difference to the time difference to obtain the change rate of the fineness test; Wherein, the time interval is measured in minutes, and the fineness is measured in μm. If the change rate of the fineness test is greater than -0.3 μm / min, it indicates that the dispersion performance of the lithium-ion battery slurry is poor; if the change rate of the fineness test is less than -0.35 μm / min, it indicates that the dispersion performance of the lithium-ion battery slurry is good.

4. The evaluation method according to claim 1 or 3, characterized in that The fineness test is carried out using a scraper fineness meter.

5. The evaluation method according to claim 1, wherein: The steps for calculating the rate of change of the viscosity test include: Calculating the viscosity difference between two adjacent viscosity tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent viscosity tests; calculating the ratio of the viscosity difference to the time difference to obtain the rate of change of the viscosity test; Wherein, the time interval is measured in minutes and the viscosity is measured in mPa.S; If the rate of change of the viscosity test is less than -150 mPa.S / min, it indicates that the dispersion performance of the lithium-ion battery slurry is good; if the rate of change of the viscosity test is greater than -100 mPa.S / min, it indicates that the dispersion performance of the lithium-ion battery slurry is poor.

6. The evaluation method according to claim 1 or 5, characterized in that The viscosity test is carried out using a viscosity tester; Optionally, the viscosity tester has a viscosity range of 0.5 to 100,000 mPa·s, a rotation speed of 10 to 30 rpm, and a temperature range of 20 to 120°C.

7. The evaluation method according to claim 1, wherein: The step of calculating the rate of change of the potential test includes: Calculating the potential difference between two adjacent potential tests of the lithium-ion battery slurry; calculating the time difference between the two adjacent potential tests; calculating the ratio of the potential difference to the time difference to obtain the rate of change of the potential test, Wherein, the time interval is measured in minutes, and the potential is measured in mV; If the rate of change of the potential test is less than 0.3 mV / min, it indicates that the dispersion performance of the lithium-ion battery slurry is poor; if the rate of change of the potential test is greater than 0.32 mV / min, it indicates that the dispersion performance of the lithium-ion battery slurry is good.

8. The evaluation method according to claim 1 or 7, characterized in that The potential test is carried out using a Zeta potential analyzer; Optionally, the Zeta potential range of the Zeta potential analyzer is -150 to 150 mV, the particle size range is 10 nm to 30 μm, the conductivity range is 0 to 200 ms / cm, the test angle is 90 degrees, and the temperature range is 2 to 90°C.

9. The evaluation method according to claim 1, wherein: The lithium-ion battery slurry is a positive electrode slurry; Optionally, the positive electrode slurry includes a positive electrode active material, a positive electrode binder, a positive electrode dispersant and a positive electrode solvent; Optionally, the solid content of the positive electrode slurry is 40-70%, preferably 50-60%; Optionally, the mass ratio of the positive electrode active material, the positive electrode binder, the positive electrode dispersant and the positive electrode solvent is (48.3-51.2): (0.7-1.3): (0.1-0.4): (48-50).

10. The evaluation method according to claim 1, wherein: The lithium-ion battery slurry is a negative electrode slurry; Optionally, the negative electrode slurry includes a negative electrode active material, a negative electrode binder, a negative electrode thickener and a negative electrode solvent; Optionally, the solid content of the negative electrode slurry is 40-70%, preferably 50-60%; Optionally, the mass ratio of the negative electrode active material, the negative electrode binder, the negative electrode thickener and the negative electrode solvent is (1.4-1.6): (0.7-0.9): (1.4-1.6): (95.9-96.5).

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