A method for detecting lithium ion slurry metal foreign matter

Abstract

The present application belongs to the technical field of lithium battery, and discloses a kind of detection method of metal foreign matter in slurry, and the specific steps are as follows: take positive or negative electrode slurry and dilute using corresponding solvent, first filtration is carried out by selecting suitable pore size filter membrane, after finishing, filter membrane is washed with solvent, then secondary filtration is carried out to washing liquid, after finishing, filter membrane is left for measurement;Another clean color filter membrane is laid on white background plate, acidic solution and oxidizing solution are added dropwise in turn, the above-mentioned filter membrane to be measured is laid on the surface of color filter membrane and infiltrated, color developing agent is added dropwise after about 1min, if colored spots appear on the surface of filter membrane, it indicates that there is metal foreign matter, the number of spots is positively correlated with the content of metal foreign matter, and the number can be used to preliminarily determine whether the slurry is qualified or not. The method is simple to operate, time-saving, low in cost, can detect production line slurry every shift, can quickly find abnormalities and handle in time, and can improve production efficiency and production stability.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion slurry detection technology, and in particular to a method for detecting metallic foreign matter in lithium-ion slurry. Background Technology

[0002] Lithium-ion batteries are widely used in energy storage, mobile devices, electric vehicles, and aerospace due to their advantages such as high energy density, long cycle life, high coulombic efficiency, and wide operating temperature range. During the manufacturing process of lithium-ion batteries, wear and tear on equipment and pipelines can introduce metallic impurities into the electrode materials, forming micro-short circuits and causing self-discharge. Therefore, most production lines use inductively coupled plasma (ICP) testing, which involves periodically sampling the slurry to quantitatively analyze whether the content of magnetic impurities exceeds the standard. This method is not only costly and time-consuming, but also involves complex testing procedures, increasing equipment and labor costs.

[0003] Chinese patent application CN110567999A discloses a SEM-EDS coupled testing method for metallic foreign matter in lithium-ion battery materials, comprising the following steps: adding high-purity water and lithium-ion cathode material to a test bottle, placing a magnet with a magnetic field strength of 5000GS-6000GS in the test bottle, and mixing thoroughly; discarding the slurry, removing the magnet, rinsing the material adhering to the magnet with high-purity water, ultrasonically washing with an ultrasonic cleaner, removing the magnet, washing and drying; adhering the magnetic foreign matter on the magnet to a conductive tape; identifying the morphology and particle size of the magnetic foreign matter particles using SEM, determining the chemical composition and type of the foreign matter particles using energy dispersive spectroscopy, and finally statistically analyzing the magnetic foreign matter content based on the determined type, quantity, and particle size of the metal-containing foreign matter particles. However, this patent does not disclose the method for detecting metallic foreign matter in lithium-ion slurry according to this invention. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a simple and low-cost method for detecting metallic foreign objects in slurry, which can quickly detect each batch of slurry and provide a judgment result.

[0005] The present invention solves the above-mentioned technical problems through the following technical means:

[0006] The present invention provides a method for detecting metallic foreign matter in lithium-ion slurry, comprising the following steps:

[0007] S1: Take the slurry to be tested, add solvent to dilute it and shake well;

[0008] S2: Perform the first filtration on the shaken slurry, discard the filtrate and retain the filter membrane;

[0009] S3: Place the filter membrane from the first filtration into a solvent for ultrasonic cleaning;

[0010] S4: Perform a second filtration on the cleaning solution, discard the filtrate, and retain the filter membrane;

[0011] S5: Place a clean filter membrane on a petri dish, add acidic solution and oxidizing solution to the surface in sequence, spread the filter membrane obtained in step S5 on the surface of the clean filter membrane, and let it stand for 1 minute.

[0012] S6: Add a color-developing agent solution to the surfaces of the two overlapping filter membranes obtained in step S5 and wait for color development. If color development occurs, it is determined that the slurry contains metallic foreign matter; if no color development occurs, it is determined that the slurry does not contain metallic foreign matter.

[0013] Preferably, in step S1, the slurry to be tested is selected from either positive or negative electrode slurries.

[0014] Preferably, in step S1, the solvent is one of deionized water and N,N-dimethylformamide (NMP).

[0015] Preferably, in step S1, the ratio of the slurry to the solvent is 1g:1.5-3mL.

[0016] Preferably, in step S1, the ratio of the slurry to the solvent is 1g:2mL.

[0017] Preferably, in step S2, the filtration specifically involves: selecting a filter membrane of appropriate specifications, cleaning it with dilute hydrochloric acid and solvent respectively, placing it in a Buchner funnel, pouring in the well-shaken slurry, and then repeatedly rinsing the container and the surface of the filter membrane with the corresponding solvent to ensure that the main material is filtered clean.

[0018] Preferably, in step S3, ultrasonic cleaning is performed for 3 to 5 minutes.

[0019] Preferably, in step S5, the clean filter membrane is a 0.22 μm filter membrane.

[0020] Preferably, in step S5, the acidic solution is selected from dilute hydrochloric acid and dilute nitric acid.

[0021] Preferably, in step S5, the oxidizing solution is a hydrogen peroxide solution.

[0022] Preferably, in step S6, the colorimetric agent is selected from potassium thiocyanate, dibenzyl dihydrazide, and dimethylglyoxime.

[0023] The beneficial effects of this invention are as follows:

[0024] This invention is simple to operate, requires little time, and is low in cost. It allows for the testing of slurry on the production line every shift, enabling rapid detection and timely handling of anomalies, thereby improving production efficiency and stability. Attached Figure Description

[0025] Figure 1This is a diagram of the filtration apparatus used in this invention;

[0026] Figure 2 This is a diagram illustrating the colorimetric experimental procedure of the present invention.

[0027] Figure labels: 1. Vacuum filter pump; 2. Wash bottle; 3. Buchner funnel; 4. Glass petri dish; 5. Filter membrane for colorimetric plate; 6. Filter membrane for colorimetric detection. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0030] Unless otherwise specified in the embodiments, the techniques or conditions described in the literature in this field or in accordance with the product manual may be followed.

[0031] Example 1:

[0032] This invention proposes a method for detecting metallic foreign matter in lithium-ion slurry.

[0033] S1: Pour 100g of nickel-cobalt-manganese cathode slurry into a homogenizing bottle, then add 200mL of N,N-dimethylformamide (NMP), and shake manually for 3-5 minutes until completely diluted and free of precipitate;

[0034] S2: Take a 30μm filter membrane, first wet it with dilute hydrochloric acid, then wet it with NMP, put it in a 60mm diameter Buchner funnel, pour in the diluted slurry and filter it, and then rinse the surface of the filter membrane several times with NMP.

[0035] S3: Place the above filter membrane into a beaker containing NMP and ultrasonically clean it for 5 minutes;

[0036] S4: Take another 30μm filter membrane, wet it with dilute hydrochloric acid and NMP, then put it into the Buchner funnel for a second filtration. After the filtration is complete, rinse the surface of the filter membrane with NMP several times.

[0037] S5: Take a 0.22μm filter membrane, wet it with dilute hydrochloric acid and NMP one after the other, then add dilute hydrochloric acid to cover the filter membrane, then add hydrogen peroxide to cover the filter membrane, spread the above-filtered filter membrane on the surface of the filter membrane, and let it stand for 1 minute.

[0038] S6: Using potassium thiocyanate (KSCN) as the colorimetric reagent, add it to the surface of the above filter membrane. After waiting for 3 to 5 minutes, a red dot will appear on the surface.

[0039] Example 2:

[0040] This invention proposes a method for detecting metallic foreign matter in lithium-ion slurry.

[0041] S1: Take 100g of negative electrode slurry from the main screw outlet and the coating head respectively, add 150mL of deionized water to each, and shake manually for 3-5 minutes until completely diluted and without precipitation.

[0042] S2: Take a 30μm filter membrane, wet it with dilute hydrochloric acid and deionized water in turn, put it into a Buchner funnel and start the sample pouring and filtration. After the filtration is completed, rinse the surface with deionized water several times.

[0043] S3: Place the above filter membrane into a beaker containing deionized water and ultrasonically clean it for 5 minutes.

[0044] S4: Take another 30μm filter membrane, wet it with dilute hydrochloric acid and deionized water, place it in a Buchner funnel for a second filtration, and rinse the surface of the filter membrane several times with deionized water after the filtration is complete.

[0045] S5: Take a 0.22μm filter membrane, wet it with dilute hydrochloric acid and deionized water, then add dilute hydrochloric acid to cover the filter membrane, then add hydrogen peroxide to cover the filter membrane, spread the above-filtered filter membrane on the surface of the filter membrane, and let it stand for 1 minute.

[0046] S6: Select KSCN as the color developer, drop it onto the surface of the above filter membrane, wait 3-5 minutes, 4 red dots appear on the filter membrane at the main screw outlet, and 0 red dots appear on the filter membrane at the coating head.

[0047] Example 3:

[0048] S1: Take 100g of positive electrode slurry from the double spiral mixing outlet and the coating head respectively and pour it into a homogenizing bottle. Add 300mL of NMP to each bottle and shake manually for 3-5 minutes until completely diluted and free of precipitate.

[0049] S2: Take a 30μm filter membrane, wet it with dilute hydrochloric acid and NMP successively, put it into a Buchner funnel and pour it for filtration. After the filtration is completed, rinse the surface with NMP several times.

[0050] S3: Place the above filter membrane into a beaker containing NMP and ultrasonically clean it for 5 minutes;

[0051] S4: Take another 30μm filter membrane, wet it with dilute hydrochloric acid and deionized water, place it in a Buchner funnel for a second filtration, and rinse the surface of the filter membrane several times with deionized water after the filtration is complete.

[0052] S5: Take a 0.22μm filter membrane, wet it with dilute hydrochloric acid and deionized water, then add dilute hydrochloric acid to cover the filter membrane, then add hydrogen peroxide to cover the filter membrane, spread the above-filtered filter membrane on the surface of the filter membrane, and let it stand for 1 minute.

[0053] S6: Select KSCN as the color developer, drop it onto the surface of the above filter membrane, wait 3-5 minutes, 8 red dots appear on the filter membrane at the double spiral stirring outlet, and 2 red dots appear on the filter membrane at the coating head.

[0054] Comparative Example 1:

[0055] To demonstrate that this invention can qualitatively determine the content of magnetic substances in the slurry, 300g of negative electrode slurry was taken from the main screw outlet and the coating head, respectively. 200g of the slurry was sent for ICP testing, and 100g was used for colorimetric reaction. The results are shown in Table 1.

[0056] Table 1

[0057] Slurry position ICP(ppb) Color reaction (number of red dots) Main screw discharge port 323.99 5 Coating head 174.57 2

[0058] As can be seen from Table 1, a method for quantitatively detecting magnetic impurities in slurry can calculate the specific content of each metal substance in ppb. This comparative example demonstrates that the colorimetric method has a certain degree of accuracy and can be used as a qualitative judgment before ICP testing.

[0059] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for detecting metallic foreign matter in lithium-ion slurry, characterized in that, Includes the following steps: S1: Take the slurry to be tested, add solvent to dilute it and shake well; the solvent is one of deionized water and N,N-dimethylformamide (NMP); S2: Perform the first filtration on the shaken slurry, discard the filtrate and retain the filter membrane; S3: Place the filter membrane from the first filtration into a solvent for ultrasonic cleaning; S4: Perform a second filtration on the cleaning solution, discard the filtrate, and retain the filter membrane; S5: Place a clean filter membrane on a petri dish, add acidic solution and oxidizing solution to the surface in sequence, spread the filter membrane obtained in step S4 on the surface of the clean filter membrane, and let it stand. S6: Add a color-developing agent solution to the surfaces of the two overlapping filter membranes obtained in step S5 and wait for color development. If color develops, it is determined that the slurry contains metallic foreign matter; if no color develops, it is determined that the slurry does not contain metallic foreign matter. The colorimetric agent is one of potassium thiocyanate, dibenzyl dihydrazide, or dimethylglyoxime.

2. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S1, the slurry to be tested is selected from either positive or negative electrode slurries.

3. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S1, the solvent is N,N-dimethylformamide (NMP).

4. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S1, the ratio of the slurry to the solvent is 1g:1.5~3mL.

5. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S2, the filtration process is as follows: Select a filter membrane of appropriate specifications, clean it with dilute hydrochloric acid and solvent respectively, place it in a Buchner funnel, pour in the well-shaken slurry, and then repeatedly rinse the container and the surface of the filter membrane with the corresponding solvent to ensure that the main material is filtered clean.

6. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S3, ultrasonic cleaning is performed for 3-5 minutes.

7. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S5, the clean filter membrane is a 0.22 μm filter membrane.

8. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S5, the acidic solution is selected from dilute hydrochloric acid and dilute nitric acid.

9. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S5, the oxidizing solution is a hydrogen peroxide solution.

10. The method for detecting metallic foreign matter in lithium-ion slurry according to claim 1, characterized in that, In step S6, the colorimetric agent is selected from potassium thiocyanate.

Images