A method for rapidly measuring the storage viscosity of battery slurry

Abstract

The application provides a method for quickly measuring storage viscosity of battery slurry, and relates to the field of analytical detection technology.The application adopts a rheometer to perform three-stage thixotropy testing on the battery slurry, to reconstruct the process from high shear in the reconstitution stage to low shear in the storage stabilization stage, simulate the viscosity change of the battery slurry from completion of dispersion to static storage, and predict the storage viscosity of the battery slurry in this way.The method provided by the application can quickly and highly accurately measure the storage viscosity of the battery slurry after long-time storage, is time-saving and highly efficient, does not need multiple sampling, reduces waste of the slurry, and provides an effective way for realizing control of qualified products of the battery slurry.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of analytical detection technology, in particular to a method for rapidly measuring the storage viscosity of battery slurry. BACKGROUND

[0002] In the production process of a battery, such as a lithium ion battery, the coating process directly affects the quality of the subsequent battery production, and the viscosity of the battery slurry during coating directly affects the coating process and quality. Therefore, the battery slurry with appropriate coating viscosity is one of the key conditions for battery preparation. The battery slurry is a non-Newtonian fluid, and its viscosity increases with the increase of storage time. However, the battery slurry is not coated immediately after stirring, but needs to be stored in a buffer tank and a transfer tank for use. Therefore, after the stirring process is completed, the storage viscosity of the slurry needs to be evaluated, especially when new materials or new processes are used, the storage viscosity of the prepared slurry should be evaluated.

[0003] The existing test method for the storage viscosity of battery slurry usually involves sampling and testing the viscosity of the battery slurry at multiple time points (initial, 12h, 24h, 36h, 48h, etc.) during long-term static or slow stirring of the battery slurry. The existing evaluation method for the storage viscosity of battery slurry requires a long time to obtain the evaluation results, resulting in low efficiency of the evaluation process, and the multiple sampling causes a large waste of slurry. SUMMARY

[0004] Therefore, the present application aims to provide a method for rapidly measuring the storage viscosity of battery slurry. The method provided by the present application can rapidly and accurately measure the storage viscosity of battery slurry, is time-saving and efficient, does not require multiple sampling, and reduces the waste of battery slurry.

[0005] In order to achieve the above-mentioned application purpose, the present application provides the following technical solutions:

[0006] The present application provides a method for rapidly measuring the storage viscosity of battery slurry, comprising the following steps:

[0007] (1) using a plurality of battery slurry samples prepared by different stirring line speeds as standard test samples;

[0008] (2) sampling from the standard test samples, and respectively performing three-stage thixotropy tests on the samples using a rheometer, wherein the three-stage thixotropy test comprises a static stage, a reconstruction stage and a storage stability stage performed in sequence; the static stage is to perform a first shearing to a steady state on the standard test sample at a constant shearing rate of 0.001-0.2 s -1 ; the reconstruction stage is to perform a second shearing on the battery slurry obtained in the static stage at a constant shearing rate of 400-1000 s -1a second shearing to a steady state at a constant shearing rate; a storage stabilization stage of shearing the battery slurry obtained in the reconstitution stage at a constant shearing rate of 0.001-0.2 s -1 a third shearing to a steady state at a constant shearing rate; calculating the rate of change of the viscosity of the battery slurry at the storage stabilization stage steady state relative to the viscosity of the battery slurry at the reconstitution stage steady state to obtain the three-stage thixotropy test viscosity change rate of each standard test sample;

[0009] from the standard test samples, another sample is taken for static storage, and the initial viscosity and storage viscosity of each standard test sample before and after static storage are measured respectively using a viscometer, and the rate of change of the storage viscosity relative to the initial viscosity is calculated to obtain the storage viscosity change rate of each standard test sample;

[0010] (3) taking the three-stage thixotropy test viscosity change rate of each standard test sample as the abscissa and the storage viscosity change rate of each standard test sample as the ordinate, and performing linear fitting to obtain a standard curve;

[0011] (4) using a viscometer to measure the initial viscosity of the battery slurry sample to be tested; the battery slurry sample to be tested is subjected to a three-stage thixotropy test according to the step (2), and the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested is calculated; the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested is substituted into the standard curve of step (3) to obtain the storage viscosity change rate of the battery slurry sample to be tested, and then combined with the initial viscosity of the battery slurry sample to be tested to obtain the storage viscosity of the battery slurry sample to be tested.

[0012] Preferably, the difference between the values of the adjacent stirring line speeds in step (1) is 1-3 m / s; and the number of standard test samples is ≥5.

[0013] Preferably, the battery slurry composition of the standard test sample and the battery slurry sample to be tested comprises an active material, a binder, a conductive agent and an organic solvent; the active material is one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate and lithium cobaltate; the binder is polyvinylidene fluoride; the conductive agent is one or more of carbon nanotubes, carbon black, conductive carbon fiber and graphene; and the organic solvent is N-methyl pyrrolidone.

[0014] Preferably, the mass percentage of the active material, the binder and the conductive agent is 95.8-98.4%, 1.2-3.0% and 0.4-1.2% respectively, based on the total mass of the active material, the binder and the conductive agent; and the mass percentage of the organic solvent in the battery slurry is 25-40%.

[0015] Preferably, the method for preparing the battery slurry of the standard test sample and the battery slurry sample to be tested comprises the following steps:

[0016] dissolving the adhesive in part of the organic solvent to obtain an adhesive solution;

[0017] mixing the adhesive solution, the conductive agent and the remaining organic solvent by first stirring to obtain a mixed liquid;

[0018] mixing the mixed liquid and the active material by second stirring to obtain the battery slurry.

[0019] Preferably, the stirring linear speed of the first stirring is 1.5-5 m / s and the time is 25-35 min; the stirring linear speed of the second stirring is 5-17 m / s and the time is 120-180 min.

[0020] Preferably, the time of the first shearing in step (2) is 50-150 s and the viscosity value of the battery slurry is read every second.

[0021] Preferably, the time of the second shearing in step (2) is 40-80 s and the viscosity value of the battery slurry is read every second.

[0022] Preferably, the time of the third shearing in step (2) is 50-150 s and the viscosity value of the battery slurry is read every second.

[0023] Preferably, the viscosity of the battery slurry after the steady state of the rebuilding stage is the average of the last 20 viscosity values read in the second shearing, and the viscosity of the battery slurry after the steady state of the storage stabilization stage is the average of the last 20 viscosity values read in the third shearing.

[0024] The present application provides a method for quickly measuring the storage viscosity of battery slurry. The present application uses a rheometer to perform three-stage thixotropy testing on the battery slurry, to simulate the viscosity change of the battery slurry from completion of dispersion to static storage through the process from high shearing in the rebuilding stage to low shearing in the storage stabilization stage, so as to predict the storage viscosity of the battery slurry. The method provided by the present application can quickly and accurately measure the storage viscosity of the battery slurry after long-time storage, with short time consumption and high efficiency; and without the need for multiple sampling, the method reduces slurry waste, and provides an effective way for the control of qualified battery slurry. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 the 3ITT curves of the standard test samples numbered ①-⑤ in Example 1;

[0026] Figure 2 the standard curve of the 3ITT viscosity change rate x of the battery slurry and the storage viscosity change rate y of the battery slurry in Example 1;

[0027] Figure 3A 3ITT curve of standard test samples of serial numbers ⑥-⑩ in Example 2;

[0028] Figure 4 A standard curve of x and y of the 3ITT viscosity change rate of the battery slurry in Example 2 and the storage viscosity change rate of the battery slurry. DETAILED DESCRIPTION

[0029] The present application provides a method for rapidly measuring the storage viscosity of a battery slurry, comprising the following steps:

[0030] (1) taking a plurality of battery slurry samples prepared by different stirring line speeds as standard test samples;

[0031] (2) sampling from the standard test samples and respectively using a rheometer to perform a three-stage thixotropy test, the three-stage thixotropy test comprising a static stage, a reconstruction stage and a storage stability stage performed in sequence; the static stage is to perform a first shearing to a steady state on the standard test sample at a constant shearing rate of 0.001-0.2 s -1 ; the reconstruction stage is to perform a second shearing to a steady state on the battery slurry obtained in the static stage at a constant shearing rate of 400-1000 s -1 ; the storage stability stage is to perform a third shearing to a steady state on the battery slurry obtained in the reconstruction stage at a constant shearing rate of 0.001-0.2 s -1 ; calculating the change rate of the viscosity of the battery slurry after the steady state of the storage stability stage relative to the viscosity of the battery slurry after the steady state of the reconstruction stage to obtain the three-stage thixotropy test viscosity change rate of each standard test sample;

[0032] sampling from the standard test samples and respectively using a rheometer to perform a three-stage thixotropy test, the three-stage thixotropy test comprising a static stage, a reconstruction stage and a storage stability stage performed in sequence; the static stage is to perform a first shearing to a steady state on the standard test sample at a constant shearing rate of 0.001-0.2 s -1 ; the reconstruction stage is to perform a second shearing to a steady state on the battery slurry obtained in the static stage at a constant shearing rate of 400-1000 s -1 ; the storage stability stage is to perform a third shearing to a steady state on the battery slurry obtained in the reconstruction stage at a constant shearing rate of 0.001-0.2 s -1 ; calculating the change rate of the viscosity of the battery slurry after the steady state of the storage stability stage relative to the viscosity of the battery slurry after the steady state of the reconstruction stage to obtain the three-stage thixotropy test viscosity change rate of each standard test sample;

[0033] (3) taking the three-stage thixotropy test viscosity change rate of each standard test sample as the abscissa and the storage viscosity change rate of each standard test sample as the ordinate, and performing linear fitting to obtain a standard curve;

[0034] (4) using a viscosity meter to measure the initial viscosity of a battery slurry sample to be tested; performing a three-stage thixotropy test on the battery slurry sample to be tested according to the step (2) to obtain the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested; substituting the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested into the standard curve of step (3) to obtain the storage viscosity change rate of the battery slurry sample to be tested, and combining the initial viscosity of the battery slurry sample to be tested to obtain the storage viscosity of the battery slurry sample to be tested.

[0035] The present application takes a plurality of battery slurry samples prepared by different stirring line speeds as standard test samples. In the present application, the difference between the values of adjacent stirring line speeds is preferably 1-3 m / s, more preferably 2 m / s; the number of the standard test samples is preferably ≥5. In the present application, the composition of the battery slurry of the standard test samples preferably comprises active material, adhesive, conductive agent and organic solvent; the active material is preferably one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate and lithium cobaltate; the adhesive is preferably polyvinylidene fluoride; the conductive agent is preferably one or more of carbon nanotube, carbon black, conductive carbon fiber and graphene; the organic solvent is preferably N-methyl pyrrolidone. In the present application, the mass percentage of the active material, adhesive and conductive agent is preferably 95.8-98.4%, 1.2-3.0% and 0.4-1.2%, respectively, based on the total mass of the active material, adhesive and conductive agent; the mass percentage of the organic solvent in the battery slurry is preferably 25-40%. In the present application, the preparation method of the battery slurry of the standard test samples preferably comprises the following steps: dissolving the adhesive in part of the organic solvent to obtain an adhesive solution; first stirring and mixing the adhesive solution, conductive agent and the remaining organic solvent to obtain a mixed solution; second stirring and mixing the mixed solution with the active material to obtain the battery slurry. In the present application, the mass concentration of the adhesive solution is preferably 5-8%, and the part of the organic solvent and the remaining organic solvent constitute the total solvent; the stirring line speed of the first stirring and mixing is preferably 1.5-5 m / s, more preferably 3-4 m / s, and the time is preferably 25-35 min, more preferably 30 min; the stirring line speed of the second stirring and mixing is preferably 5-17 m / s, more preferably 7-15 m / s, and in the embodiments of the present application, the battery slurry samples obtained by the stirring line speeds of 15 m / s, 13 m / s, 11 m / s, 9 m / s and 7 m / s are taken as standard test samples; the time of the second stirring and mixing is preferably 120-180 min, more preferably 150 min. After the second stirring and mixing, the present application further preferably screens the obtained mixed solution by a screen to obtain the battery slurry, and the screen is preferably a 150-mesh screen.

[0036] After obtaining the standard test samples, the present application takes samples from the standard test samples and respectively adopts a rheometer to perform three-stage thixotropy test (i.e. 3ITT test), which comprises a static stage, a reconstitution stage and a storage stability stage in sequence. The present application does not have special requirements for the rheometer, and a rheometer well known to those skilled in the art can be adopted, and in the embodiments of the present application, the rheometer is preferably a pneumatic rheometer, which can meet the accurate control of very low shear rate. In the present application, the static stage is to take the standard test sample into the rheometer at a shear rate of 0.001-0.2 s -1to steady state; the rebuilding stage is to perform second shearing to steady state on the battery slurry obtained in the resting stage at a constant shearing rate of 400-1000 s -1 to steady state; the storing stability stage is to perform third shearing to steady state on the battery slurry obtained in the rebuilding stage at a constant shearing rate of 0.001-0.2 s -1 to steady state. In the present application, the constant shearing rate of the first shearing is further preferably 0.01-0.1 s -1 , the time of the first shearing is preferably 50-150 s, and the viscosity value of the battery slurry is read every second; the constant shearing rate of the second shearing is further preferably 500-550 s -1 , the time of the second shearing is preferably 40-80 s, and the viscosity value of the battery slurry is read every second; the constant shearing rate of the third shearing is further preferably 0.01-0.1 s -1 , the time of the third shearing is preferably 50-150 s, and the viscosity value of the battery slurry is read every second. In the present application, the resting stage is to perform low shearing disturbance on the sample, so that the sample reaches a preliminary stable state of viscosity, avoids the influence of shearing behaviors such as shaking and vibration on the sample testing process, and further ensures uniform temperature distribution (25℃) of the sample and eliminates the influence of temperature on the testing results; the rebuilding stage is to increase the shearing rate, so as to simulate the state of the battery slurry after high shearing; and the resting stage is to use a lower shearing rate, so as to simulate the state of the battery slurry in a static state.

[0037] After the three-stage thixotropy test is completed, the present application calculates the change rate of the viscosity of the battery slurry in the storing stability stage relative to the viscosity of the battery slurry in the rebuilding stage (in the present application, for the sake of simplicity, the viscosity of the battery slurry in the storing stability stage after reaching steady state is also referred to as the viscosity of the battery slurry in the storing stability stage, and the viscosity of the battery slurry in the rebuilding stage after reaching steady state is referred to as the viscosity of the battery slurry in the rebuilding stage), to obtain the three-stage thixotropy test viscosity change rate (i.e., 3ITT viscosity change rate) of each standard test sample. In the present application, the viscosity of the battery slurry in the rebuilding stage after reaching steady state is preferably the average value of 20 viscosity values read at the end of the second shearing, and the viscosity of the battery slurry in the storing stability stage after reaching steady state is preferably the average value of 20 viscosity values read at the end of the third shearing, so as to reduce errors; and the calculation formula of the three-stage thixotropy test viscosity change rate of each standard test sample is specifically shown in Formula I:

[0038] 3ITT viscosity change rate = (viscosity in the storing stability stage after reaching steady state - viscosity in the rebuilding stage after reaching steady state) / viscosity in the rebuilding stage after reaching steady state × 100% Formula I.

[0039] The present application takes another sample from the standard test sample for static storage, respectively measures the initial viscosity and storage viscosity of each standard test sample before and after static storage using a viscometer, calculates the change rate of the storage viscosity relative to the initial viscosity, and obtains the storage viscosity change rate of each standard test sample. The present application does not have special requirements for the viscometer, and a viscometer well known to those skilled in the art can be used. In the industry, the static time is usually 48 h. In the present application, the calculation formula of the storage viscosity change rate of each standard test sample is specifically shown in formula II:

[0040] Storage viscosity change rate = (storage viscosity - initial viscosity) / initial viscosity x 100% formula II.

[0041] After obtaining the three-stage thixotropy test viscosity change rate of each standard test sample and the storage viscosity change rate of each standard test sample, the present application takes the three-stage thixotropy test viscosity change rate of each standard test sample as the abscissa (x) and the storage viscosity change rate of each standard test sample as the ordinate (y), linearly fits to obtain a standard curve, which is shown in formula III:

[0042] y = f(x) formula III.

[0043] The present application measures the initial viscosity of the battery slurry sample to be tested using a viscometer; the battery slurry composition and preparation method of the battery slurry sample to be tested are the same as those in the above technical solution, and will not be described here. The present application performs three-stage thixotropy test on the battery slurry sample to be tested according to the above technical solution, and calculates the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested. The present application substitutes the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested into the standard curve in the above technical solution, obtains the storage viscosity change rate of the battery slurry sample to be tested, and then combines the initial viscosity of the battery slurry sample to be tested to obtain the storage viscosity of the battery slurry sample to be tested. Specifically, the obtained storage viscosity change rate of the battery slurry sample to be tested and the initial viscosity of the battery slurry sample to be tested are calculated according to formula II to obtain the storage viscosity of the battery slurry sample to be tested.

[0044] The method for quickly measuring the storage viscosity of the battery slurry provided by the present application will be described in detail below in combination with examples, but they should not be understood as limiting the scope of protection of the present application.

[0045] Example 1

[0046] A method for quickly measuring the storage viscosity of the battery slurry, specifically as follows:

[0047] (1) Preparation of battery slurry:

[0048] The mass percentage of non-solvent components in the battery slurry is: 1.0% conductive agent (carbon nanotubes) + 3.0% polyvinylidene fluoride + 96.0% lithium iron phosphate; the mass percentage of solvent N-methylpyrrolidone in the battery slurry is 40%.

[0049] Polyvinylidene fluoride (PVDF) was pre-dissolved in a portion of N-methylpyrrolidone to prepare an 8% PVDF solution. The conductive agent, PVDF solution, and remaining N-methylpyrrolidone were then stirred at a linear velocity of 3 m / s for 30 min using a mechanical stirrer. Lithium iron phosphate was then added and dispersed at high speeds of 15 m / s, 13 m / s, 11 m / s, 9 m / s, and 7 m / s for 150 min, respectively. The mixture was then filtered through a 150-mesh sieve. The corresponding battery slurry samples were coded as ① to ⑤ and used as standard test samples.

[0050] (2) Samples were taken from the standard test samples numbered ① to ⑤ and 3ITT tests (three-stage thixotropic test) were performed using a rheometer. The shear rate of the 3ITT static stage was constant at 0.01 / s, the test time was 100s, and the reading was taken every second. The shear rate of the 3ITT reconstruction stage was constant at 500 / s, the test time was 40s, and the reading was taken every second. The shear rate of the 3ITT storage stabilization stage was constant at 0.01 / s, the test time was 100s, and the reading was taken every second.

[0051] Obtain the 3ITT curves of standard test samples numbered ①~⑤ (e.g.) Figure 1 As shown), the viscosity of the samples in the reconstruction stage and the storage stabilization stage were compared, and the viscosity change rate was calculated. The 3ITT viscosity change rate was calculated as follows: 3ITT viscosity change rate = (storage stabilization stage viscosity - reconstruction stage viscosity) / reconstruction stage viscosity × 100%. To reduce errors, the average value of the last 20 data points was used for the reconstruction stage viscosity and the average value of the last 20 data points was used for the storage stabilization stage viscosity.

[0052] (3) Take another sample from the standard test samples ① to ⑤ and place them in 200mL beakers of the same diameter and height. Measure the initial storage viscosity using a viscometer. Then seal and let stand for 48 hours. After 48 hours, unseal and measure the 48-hour storage viscosity using a viscometer. Compare the obtained initial storage viscosity and the 48-hour storage viscosity to calculate the storage viscosity change rate. Storage viscosity change rate = (48-hour storage viscosity - initial storage viscosity) / initial storage viscosity × 100%.

[0053] The viscosity values ​​of the standard test samples numbered ① to ⑤ obtained by measurement are shown in Table 1:

[0054] Table 1. Viscosity values ​​of standard test samples ① to ⑤ in Table 1.

[0055]

[0056] (4) Standard curve drawing: taking the 3ITT viscosity change rate of the standard test sample No. ① ~ ⑤ in Table 1 as the abscissa x, and the storage viscosity change rate as the ordinate y, the above data is linearly fitted, and the standard curve relationship of the 3ITT viscosity change rate x of the battery slurry and the storage viscosity change rate y of the battery slurry is y = f(x) = 4.12 * x - 5.44 (as shown in Figure 2 ).

[0057] (5) Storage viscosity test of unknown battery slurry, as follows:

[0058] Take the unknown storage viscosity battery slurry produced in a batch, test the 3ITT viscosity change rate of the unknown storage viscosity battery slurry by the same method as step (2), and test the storage initial viscosity by the same method as step (3);

[0059] Substitute the tested 3ITT viscosity change rate of the unknown storage viscosity battery slurry into the standard curve y = f(x) = 4.12 * x - 5.44, and obtain the storage viscosity change rate of the unknown storage viscosity battery slurry, and then combine the tested storage initial viscosity to obtain the storage 48h viscosity of the unknown storage viscosity battery slurry.

[0060] Comparative Example 1

[0061] Test the storage initial viscosity and storage 48h viscosity of the unknown storage viscosity battery slurry in Example 1 by the same method as step (3).

[0062] The test data of the unknown storage viscosity battery slurry tested in Example 1 and Comparative Example 1 are listed in Table 2.

[0063] Table 2 Test data of unknown storage viscosity battery slurry in Example 1 and Comparative Example 1

[0064]

[0065] The 3ITT viscosity change rate of the battery slurry with unknown storage viscosity obtained in Example 1 is substituted into the standard curve relationship: y = f(x) = 4.12 * x - 5.44, and the storage viscosity change rate y of the battery slurry is calculated to be 218.20%, and combined with the storage initial viscosity, the storage 48h viscosity of the battery slurry is calculated to be 9387 mPa·s; the storage 48h viscosity of the battery slurry with unknown storage viscosity measured in Comparative Example 1 is 9450 mPa·s. It can be seen that the storage 48h viscosity result of the battery slurry with unknown storage viscosity measured in Example 1 is close to the storage 48h viscosity result of Comparative Example 1; after establishing the standard curve according to the method for quickly measuring the storage viscosity of the battery slurry in Example 1, the test time for the battery slurry with unknown storage viscosity is 0.15h, while the test time for each test according to the method of Comparative Example 1 is 48h, and the test time for the method for quickly measuring the storage viscosity of the battery slurry provided by the application is only 1 / 320 of that of Comparative Example 1, which greatly improves the test efficiency.

[0066] Example 2

[0067] A method for quickly measuring the storage viscosity of a battery slurry, specifically as follows:

[0068] (1) Preparation of the battery slurry:

[0069] The mass percentage of the non-solvent components in the battery slurry: 0.7% carbon nanotubes + 0.5% carbon black + 1.5% polyvinylidene fluoride + 97.3% lithium nickel cobalt manganese oxide (NCM523); the mass percentage of the solvent N-methyl pyrrolidone in the battery slurry is 35%;

[0070] The same method as in step (1) of Example 1 was used to prepare the battery slurry to obtain 5 samples coded as ⑥-⑩ as standard test samples;

[0071] (2) The rheometer was used to test the 3ITT of the standard test samples with serial numbers ⑥-⑩, the test method was the same as in step (2) of Example 1, the 3ITT curves of the standard test samples with serial numbers ⑥-⑩ were obtained (as shown in Figure 3 ), and the 3ITT viscosity change rates of the standard test samples with serial numbers ⑥-⑩ were calculated;

[0072] (3) The storage initial viscosity and the storage 48h viscosity of the standard test samples with serial numbers ⑥-⑩ were measured according to the same method as in step (3) of Example 1, and the storage viscosity change rate was calculated;

[0073] The measured viscosity values of the standard test samples with serial numbers ⑥-⑩ are shown in Table 3:

[0074] Table 3 Viscosity values of the standard test samples with serial numbers ⑥-⑩

[0075]

[0076] (4) Standard curve drawing, taking the 3ITT viscosity change rate of the standard test sample in Table 3, No. 6~No. 10 as the abscissa x, and the storage viscosity change rate as the ordinate y, linear fitting is performed on the above data, and the standard curve relationship between the 3ITT viscosity change rate x of the battery slurry and the storage viscosity change rate y of the battery slurry is: y = f(x) = 1.31 * x - 0.52 (as shown in Figure 4 ).

[0077] (5) Storage viscosity test of unknown battery slurry, specifically as follows:

[0078] Take the battery slurry with unknown storage viscosity produced in a batch, test the 3ITT viscosity change rate of the battery slurry with unknown storage viscosity by the same method as step (2), and test the storage initial viscosity by the same method as step (3);

[0079] Substitute the tested 3ITT viscosity change rate of the battery slurry with unknown storage viscosity into the standard curve y = f(x) = 1.31 * x - 0.52, to obtain the storage viscosity change rate of the battery slurry with unknown storage viscosity, and then combine the tested storage initial viscosity to obtain the storage 48h viscosity of the battery slurry with unknown storage viscosity.

[0080] Comparative Example 2

[0081] Test the storage initial viscosity and the storage 48h viscosity of the battery slurry with unknown storage viscosity in Example 2 by the same method as step (3).

[0082] The test data of the battery slurry with unknown storage viscosity tested in Example 2 and Comparative Example 2 are listed in Table 4.

[0083] Table 4 Test data of the battery slurry with unknown storage viscosity in Example 2 and Comparative Example 2

[0084]

[0085] Substitute the 3ITT viscosity change rate of the battery slurry with unknown storage viscosity obtained in Example 2 into the function relationship y = f(x) = 1.31 * x - 0.52, and calculate that the storage viscosity change rate y of the battery slurry is 196.90%, and then combine the storage initial viscosity to calculate that the storage 48h viscosity of the battery slurry is 9530 mPa·s. It can be seen that the storage 48h viscosity result measured in Example 2 is close to the storage 48h viscosity result (9480 mPa·s) measured in Comparative Example 2.

[0086] From the above examples, it can be seen that the application can quickly and accurately measure the storage viscosity of the battery slurry after long-time storage, and has short time consumption and high efficiency.

[0087] The above only describes the preferred embodiments of the present application, and it should be noted that those skilled in the art can make several improvements and refinements without departing from the principles of the present application, and these improvements and refinements should also be considered within the protection scope of the present application.

Claims

1. A method for rapidly measuring the storage viscosity of a battery slurry, characterized by, The method comprises the following steps: (1) taking a plurality of battery slurry samples prepared by different stirring speeds as standard test samples; (2) sampling from the standard test samples, respectively using a rheometer to perform three-stage thixotropy tests, the three-stage thixotropy tests comprising a static stage, a reconstitution stage and a storage stability stage performed in sequence; the rest phase is a first shearing to steady state at a constant shearing rate of 0.001-0.2 s -1 -1 for the standard test sample; the rebuild phase is a second shearing to steady state at a constant shearing rate of 400-1000 s -1 -1 for the battery slurry obtained in the rest phase; the storage stability phase is a third shearing to steady state at a constant shearing rate of 0.001-0.2 s -1 -1 for the battery slurry obtained in the rebuild phase; the three-phase thixotropy test viscosity change rate of each standard test sample is calculated by calculating the change rate of the viscosity of the battery slurry at the steady state of the storage stability phase relative to the viscosity of the battery slurry at the steady state of the rebuild phase; sampling from the standard test samples to perform static storage, respectively measuring initial viscosity and storage viscosity of each standard test sample before and after static storage using a viscometer, calculating the change rate of the storage viscosity relative to the initial viscosity to obtain the storage viscosity change rate of each standard test sample; (3) taking the three-stage thixotropy test viscosity change rate of each standard test sample as the horizontal coordinate, taking the storage viscosity change rate of each standard test sample as the vertical coordinate, performing linear fitting to obtain a standard curve; (4) measuring the initial viscosity of the battery slurry sample to be tested using a viscometer; performing three-stage thixotropy tests on the battery slurry sample to be tested according to the step (2) to calculate the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested; substituting the three-stage thixotropy test viscosity change rate of the battery slurry sample to be tested into the standard curve of step (3) to obtain the storage viscosity change rate of the battery slurry sample to be tested, and combining the initial viscosity of the battery slurry sample to be tested to obtain the storage viscosity of the battery slurry sample to be tested.

2. The method of claim 1, wherein, The difference between the values of adjacent stirring speeds in the step (1) is 1-3 m / s; the number of the standard test samples is ≥5.

3. The method of claim 1, wherein, The battery slurry composition of the standard test samples and the battery slurry sample to be tested comprises active material, adhesive, conductive agent and organic solvent; the active material is one or more of lithium nickel cobalt manganese oxide, lithium iron phosphate and lithium cobaltate; the adhesive is polyvinylidene fluoride; the conductive agent is one or more of carbon nanotube, carbon black, conductive carbon fiber and graphene; the organic solvent is N-methyl pyrrolidone.

4. The method of claim 3, wherein, The mass percentage of the active material, adhesive and conductive agent is 95.8-98.4%, 1.2-3.0% and 0.4-1.2% respectively, based on the total mass of the active material, adhesive and conductive agent; the mass percentage of the organic solvent in the battery slurry is 25-40%.

5. The method according to claim 3 or 4, characterized in that, The battery slurry preparation method of the standard test samples and the battery slurry sample to be tested comprises the following steps: dissolving the adhesive in part of the organic solvent to obtain an adhesive solution; performing first stirring and mixing of the adhesive solution, conductive agent and the remaining organic solvent to obtain a mixed liquid; performing second stirring and mixing of the mixed liquid and active material to obtain a battery slurry.

6. The method of claim 5, wherein, The stirring speed of the first stirring and mixing is 1.5-5 m / s, and the time is 25-35 min; the stirring speed of the second stirring and mixing is 5-17 m / s, and the time is 120-180 min.

7. The method of claim 1, wherein, The time of the first shearing in the step (2) is 50-150 s, and the battery slurry viscosity value is read every second.

8. The method of claim 1, wherein, The time of the second shearing in the step (2) is 40-80 s, and the battery slurry viscosity value is read every second.

9. The method of claim 1, wherein, The third shearing in step (2) is for 50-150 seconds, and the battery slurry viscosity value is read every second.

10. The method according to claim 8 or 9, characterized in that, The viscosity of the battery slurry after the reestablishment stage is stable is the average of the last 20 viscosity values read in the second shearing, and the viscosity of the battery slurry after the storage stabilization stage is stable is the average of the last 20 viscosity values read in the third shearing.

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