A diluent for detecting magnetic substances in a positive electrode slurry and a method of use

Abstract

The application discloses a kind of diluent for detecting positive paste magnetic substance and use method, it is related to lithium battery material detection technical field, diluent includes following component: mass ratio is 70-90% N-methyl pyrrolidone, mass ratio is 5-15% polyether modified organosiloxane and mass ratio is 5-15% organic solvent, the use method of diluent includes the following steps: take 200g positive paste with 250mL diluent is added in 500mL wide mouth round body's plastic bottle, plastic bottle is added in magnet, cover good inner cover, with sealing film sealing inner cover, sample is shaken, plastic bottle is placed on ball mill and the material in bottle is vibrated and broken down;Plastic bottle is taken off, and the magnet is sucked, and the material is poured out, and then the magnet in the plastic bottle is cleaned with diluent;The application can effectively remove the positive paste adhered to the magnet, avoid the influence of the slurry on the magnetic substance content test, and the method avoids using ultrasonic cleaning magnet, improves the accuracy of test results.

Description

Technical Field

[0001] This invention relates to the field of lithium battery material testing technology, specifically to a diluent for detecting magnetic materials in positive electrode slurry and its application method. Background Technology

[0002] Lithium-ion batteries are rechargeable batteries that primarily function by the movement of lithium ions between the positive and negative electrodes. Compared to other battery types, lithium-ion batteries have higher energy density and longer cycle life. Detecting the content of magnetic materials in lithium-ion batteries is crucial for battery safety. During charging, these magnetic particles oxidize and dissolve into metal ions at the positive electrode, reaching the electrode through the separator. During discharging, these metal ions are first reduced to elemental metals at the negative electrode. Organic matter in the electrolyte then uses these ions as seed crystals to continue agglomerating and growing, forming angular or dendritic structures. This continuous growth can puncture the battery separator, causing an internal short circuit and rapid self-discharge.

[0003] The conventional method for testing magnetic materials in cathode raw materials involves thoroughly stirring the material with a high-strength magnetic rod to adsorb the magnetic materials, then adding a strong acid to dissolve them, and finally detecting the elemental content of Fe, Ni, Zn, Cr, and Cu using ICP. In lithium-ion battery production, the mixing tank is made of stainless steel, and magnetic materials may be introduced during the homogenization process. Therefore, monitoring the content of magnetic materials in the slurry is particularly important. Because the cathode slurry contains a certain proportion of binders (such as polyvinylidene fluoride), the slurry adheres to the magnetic rod during the pretreatment process for testing magnetic materials and cannot be removed. This results in the magnetic rod containing a large amount of cathode slurry and the magnetic particles to be tested, severely affecting the accuracy of the magnetic material test results. Therefore, a diluent and its application method for detecting magnetic materials in cathode slurry are needed to solve the above problems. Summary of the Invention

[0004] The purpose of this invention is to provide a diluent for detecting magnetic materials in positive electrode slurry and a method for using it, so as to solve the problems existing in the prior art mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] A diluent for detecting magnetic materials in positive electrode slurry comprises the following components: 70-90% N-methylpyrrolidone by mass, 5-15% polyether-modified organosiloxane by mass, and 5-15% organic solvent by mass.

[0007] Preferably, the organic solvent is one of ethanol, ethyl acetate, and ethyl propionate.

[0008] This invention also provides a method for using a diluent for detecting magnetic materials in positive electrode slurry, comprising the following steps:

[0009] S1: Take 200g of positive electrode slurry and 250mL of diluent and add them to a 500mL wide-mouth round plastic bottle. Add a magnetic rod to the plastic bottle, close the inner cap, seal the inner cap with sealing film, shake the sample well, and place the plastic bottle on a ball mill to vibrate and crush the contents of the bottle.

[0010] S2: Remove the plastic bottle, hold the magnetic rod, pour out the material, and then clean the magnetic rod in the plastic bottle with thinner;

[0011] S3: Transfer the magnetic rod to a triangular beaker, add 20mL of aqua regia to submerge the magnetic rod, and heat at 200℃ for 30min.

[0012] S4: Transfer the heated solution to a volumetric flask and make up to volume. Then test the content of Fe, Ni, Zn, Cr and Cu elements. The sum of the element contents is the content of magnetic material.

[0013] Preferably, the rotational speed of the ball mill is set to 120±5 rpm, and the working time is set to 30±3 min.

[0014] Compared with the prior art, the beneficial effects of the present invention are:

[0015] 1. This invention can effectively remove the positive electrode slurry adhering to the magnetic rod, avoiding the influence of the slurry on the magnetic material content test. In addition, this method avoids the use of ultrasonic cleaning of the magnetic rod, thus improving the accuracy of the test results.

[0016] 2. This invention shortens the testing time for magnetic material content, improves testing efficiency, and the diluent used in the testing process is a common consumable in the laboratory, which is easy to obtain and economical. Attached Figure Description

[0017] Figure 1-6 The images show the magnetic rod adsorption effects of comparative examples 1-6 in this invention.

[0018] Figure 7-10 The images show the magnetic rod adsorption effect of Examples 1-4 in this invention. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0020] Please see Figure 1-10 The present invention provides the following technical solutions:

[0021] Comparative Example 1

[0022] S1: Use N-methylpyrrolidone to prepare the diluent. Take 200g of positive electrode slurry and 250mL of diluent and add them to a 500mL wide-mouth round plastic bottle. Add a magnetic rod to the plastic bottle, close the inner cap, seal the inner cap with sealing film, shake the sample well, and place the plastic bottle on a ball mill to vibrate and crush the contents. The speed of the ball mill is set to 120±5rpm and the working time is set to 30±3min.

[0023] S2: Remove the plastic bottle, hold the magnetic rod, pour out the material, and then clean the magnetic rod in the plastic bottle with thinner;

[0024] S3: Transfer the magnetic rod to a triangular beaker, add 20mL of aqua regia to submerge the magnetic rod, and heat at 200℃ for 30min.

[0025] S4: Transfer the heated solution to a volumetric flask and make up to volume. Then test the content of Fe, Ni, Zn, Cr and Cu elements. The sum of the element contents is the content of magnetic material.

[0026] Comparative Example 2

[0027] With all other operations remaining unchanged, the difference between Comparative Example 2 and Comparative Example 1 is that Comparative Example 2 uses ethanol to prepare the diluent.

[0028] Comparative Example 3

[0029] With other operations remaining unchanged, the difference between Comparative Example 3 and Comparative Example 1 is that the diluent was prepared according to a mass ratio of 90% N-methylpyrrolidone and 10% polyether-modified organosiloxane.

[0030] Comparative Example 4

[0031] With all other operations remaining unchanged, the difference between Comparative Example 4 and Comparative Example 1 is that the diluent was prepared according to a mass ratio of 90% N-methylpyrrolidone and 10% ethanol.

[0032] Comparative Example 5

[0033] With other operations remaining unchanged, the difference between Comparative Example 5 and Comparative Example 1 is that the diluent was prepared according to a mass ratio of 10% polyether-modified organosiloxane and 90% ethanol.

[0034] Comparative Example 6

[0035] With other operations remaining unchanged, the difference between Comparative Example 6 and Comparative Example 1 is that the diluent was prepared according to the mass ratio of 60% N-methylpyrrolidone, 20% polyether-modified organosiloxane and 20% ethanol.

[0036] like Figure 1-6 As shown, in Comparative Examples 1 and 2, when N-methylpyrrolidone or ethanol was used alone as a diluent, a large amount of slurry adhered to the magnetic rod and could not be removed.

[0037] In Comparative Example 3, ethanol was removed, and 90% N-methylpyrrolidone and 10% polyether-modified organosiloxane were used as diluents. However, a significant amount of slurry remained on the magnetic rod and could not be completely removed.

[0038] In Comparative Example 4, the polyether-modified organosiloxane was removed, and 90% N-methylpyrrolidone and 10% ethanol were used as diluents. A large amount of slurry remained on the magnetic rod and could not be completely removed. In Comparative Example 5, the N-methylpyrrolidone was removed, and 90% ethanol and 10% polyether-modified organosiloxane were used as diluents. A large amount of slurry remained on the magnetic rod and could not be completely removed.

[0039] In Comparative Example 6, the proportion of N-methylpyrrolidone in the diluent was reduced. The diluent was prepared using 60% N-methylpyrrolidone, 20% polyether-modified organosiloxane, and 20% ethanol. The magnetic rod had a lower slurry viscosity, but the expected effect was not achieved.

[0040] Example 1

[0041] S1: Prepare a diluent according to the mass ratio of 80% N-methylpyrrolidone, 10% polyether-modified organosiloxane and 10% ethanol. Take 200g of positive electrode slurry and 250mL of diluent and add them to a 500mL wide-mouth round plastic bottle. Add a magnetic rod to the plastic bottle, close the inner cap, seal the inner cap with sealing film, shake the sample well, and place the plastic bottle on a ball mill to vibrate and crush the contents of the bottle. The speed of the ball mill is set to 120±5rpm and the working time is set to 30±3min.

[0042] S2: Remove the plastic bottle, hold the magnetic rod, pour out the material, and then clean the magnetic rod in the plastic bottle with thinner;

[0043] S3: Transfer the magnetic rod to a triangular beaker, add 20mL of aqua regia to submerge the magnetic rod, and heat at 200℃ for 30min.

[0044] S4: Transfer the heated solution to a volumetric flask and make up to volume. Then test the content of Fe, Ni, Zn, Cr and Cu elements. The sum of the element contents is the content of magnetic material.

[0045] Example 2

[0046] The difference between Example 2 and Example 1 is that, with all other operations remaining unchanged, the diluent is prepared according to the mass ratio of 70% N-methylpyrrolidone, 15% polyether-modified organosiloxane, and 15% ethanol.

[0047] Example 3

[0048] The difference between Example 3 and Example 1 is that, with all other operations remaining unchanged, the diluent is prepared according to the mass ratio of 90% N-methylpyrrolidone, 5% polyether-modified organosiloxane and 5% ethanol.

[0049] Example 4

[0050] The difference between Example 4 and Example 1 is that, with all other operations remaining unchanged, the diluent was prepared according to the mass ratio of 80% N-methylpyrrolidone, 10% polyether-modified organosiloxane, and 10% ethyl acetate.

[0051] like Figure 7-10 As shown, in Example 1, a diluent was prepared using 80% N-methylpyrrolidone, 10% polyether-modified organosiloxane, and 10% ethanol. This is a preferred example of the present invention. It can be seen that there is no slurry adhering to the magnetic rod, achieving the expected effect of the magnetic material content test.

[0052] In Example 2, the mass ratio of N-methylpyrrolidone was appropriately reduced, while the mass ratio of polyether-modified organosiloxane and ethanol was increased. It can be seen that there was no slurry adhering to the magnetic rod, achieving the expected effect of the magnetic material content test.

[0053] In Example 3, the mass ratio of N-methylpyrrolidone was appropriately increased, while the mass ratio of polyether-modified organosiloxane and ethanol was decreased. It can be seen that there was no slurry adhering to the magnetic rod, achieving the expected effect of the magnetic material content test.

[0054] In Example 4, ethanol was replaced with ethyl acetate, and it can be seen that no slurry adhered to the magnetic rod, achieving the expected effect of the magnetic material content test.

[0055] Comparison table of magnetic material content test data for lithium iron phosphate cathode slurry:

[0056]

[0057] By comparing the magnetic material content in lithium iron phosphate cathode slurry, it can be seen that the Fe and P content is relatively high in the comparative example. Most of the Fe content detected in the comparative example comes from the Fe in the lithium iron phosphate material, which seriously affects the accuracy of the magnetic material content test.

[0058] Furthermore, the diluent of this invention did not detect any phosphorus (P) content in the test data, indicating that the test was not affected by lithium iron phosphate powder, which greatly improved the accuracy of the test results.

[0059] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A diluent for detecting magnetic materials in positive electrode slurry, characterized in that, It comprises the following components: 70-90% N-methylpyrrolidone by mass, 5-15% polyether-modified organosiloxane by mass, and 5-15% organic solvent by mass; wherein the organic solvent is one of ethanol, ethyl acetate, and ethyl propionate.

2. A method for using the diluent for detecting magnetic materials in positive electrode slurry according to claim 1, characterized in that, Includes the following steps: S1: Take 200g of positive electrode slurry and 250mL of diluent and add them to a 500mL wide-mouth round plastic bottle. Add a magnetic rod to the plastic bottle, close the inner cap, seal the inner cap with sealing film, shake the sample well, and place the plastic bottle on a ball mill to vibrate and crush the contents of the bottle. S2: Remove the plastic bottle, hold the magnetic rod, pour out the material, and then clean the magnetic rod in the plastic bottle with thinner; S3: Transfer the magnetic rod to a triangular beaker, add 20mL of aqua regia to submerge the magnetic rod, and heat at 200℃ for 30min. S4: Transfer the heated solution to a volumetric flask and make up to volume. Then test the content of Fe, Ni, Zn, Cr and Cu elements. The sum of the element contents is the content of magnetic material.

3. The method of using the diluent for detecting magnetic materials in positive electrode slurry according to claim 2, characterized in that, The ball mill's rotational speed is set to 120±5 rpm, and the working time is set to 30±3 min.

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