Dispersing agent, preparation method thereof and method for detecting content of magnetic foreign matters

Abstract

The invention discloses a dispersing agent, a preparation method thereof and a method for detecting the content of magnetic foreign matters, the dispersing agent comprises a compound shown as a formula I, R1 comprises a hydrogen atom or R2 comprises-(CH2) x-, 1 < = x < = 6, 10 < = n < = 50, R3 comprises a substituent group containing a benzene ring, and m > = 2. Therefore, the positive electrode active material can be directly dispersed in water to test the content of the magnetic foreign matters in the positive electrode active material, the extraction efficiency of the magnetic foreign matters is improved, the test process is simplified, and the test cost is reduced.

Description

Technical Field

[0001] This application relates to the field of batteries, and more specifically, to dispersants, methods for their preparation, and methods for detecting the content of magnetic foreign matter. Background Technology

[0002] In recent years, with the increasingly wide range of applications, batteries have been widely used in energy storage power systems such as hydropower, thermal power, wind power, and solar power plants, as well as in power tools, electric bicycles, electric motorcycles, electric cars, military equipment, aerospace, and many other fields. During the preparation of battery positive electrode active materials, magnetic foreign matter (such as Fe, Cr, Bi, and other metallic foreign matter) is inevitably introduced. During battery charging and discharging, the introduction of magnetic foreign matter increases the risk of metal dendrite formation on the negative electrode and increases the probability of self-discharge. Therefore, it is necessary to monitor the content of magnetic foreign matter in the positive electrode active material. In related technologies, the magnetic foreign matter content testing process often uses N-methylpyrrolidone (NMP) as a solvent to disperse the positive electrode active material into a slurry, and then extracts the magnetic foreign matter from the slurry for testing. However, the magnetic foreign matter extraction rate is low, and the entire testing process is inefficient and costly. Summary of the Invention

[0003] In view of the technical problems existing in the background art, this application provides a dispersant that can improve the uniformity of dispersion of positive electrode active material in water, improve the extraction rate of magnetic foreign matter, and improve the efficiency of magnetic foreign matter testing.

[0004] A first aspect of this application provides a dispersant comprising a compound of formula I:

[0005] Wherein, R1 includes hydrogen atoms or

[0006] R2 includes -(CH2) x -, 1≤x≤6, 10≤n≤50, R3

[0007] Including substituents containing benzene rings, m≥2. Therefore, the carbamate groups and benzene ring structure in the dispersant have a strong anchoring effect on the positive electrode active material, and the polyether segments can improve the binding force with water molecules. Thus, this dispersant can be used to directly disperse the positive electrode active material in water for the extraction of magnetic foreign matter, improving the extraction efficiency of magnetic foreign matter, increasing the efficiency of magnetic foreign matter testing, and reducing testing costs.

[0008] According to some embodiments of this application, the dispersant satisfies one or more of the following conditions: 2 ≤ m ≤ 6; R3 includes one or both of benzyl or diphenylmethane. This improves the dispersion effect of the dispersant on the positive electrode active material.

[0009] According to some embodiments of this application, the compound represented by Formula I includes:

[0010] Therefore, dispersants that form a BAB structure can create steric hindrance in a V-shaped structure, further improving the dispersion effect of the dispersant.

[0011] According to some embodiments of this application, the compound represented by Formula I includes

[0012]

[0013] Therefore, dispersants that form a BAB structure can create steric hindrance in a V-shaped structure, further improving the dispersion effect of the dispersant.

[0014] The second aspect of this application provides a method for preparing the dispersant of the first aspect of this application, comprising: dehydrating a monohydric alcohol or dihydric alcohol and mixing it with a cyanate ester compound, then heating the mixture to obtain a first product; cooling the first product and mixing it with an R3 source, reacting the mixture to obtain a second product, wherein the R3 source includes an aromatic hydrocarbon; cooling the second product and mixing it with an R2 source, reacting the mixture to obtain the dispersant shown in Formula I, wherein the R2 source includes an epoxy compound. Thus, the dispersant prepared by this method possesses all the features and advantages of the dispersant provided in the first aspect of this application, which will not be elaborated further here. In summary, the dispersant prepared by this method can improve the uniformity of dispersion of positive electrode active materials in water, improve the extraction efficiency of magnetic foreign matter, improve the testing efficiency of magnetic foreign matter, and reduce testing costs.

[0015] According to some embodiments of this application, the method satisfies one or more of the following conditions: the monohydric alcohol includes one or more of ethanol, propanol, butanol, and hexanol; the dihydric alcohol includes one or more of 1,2-propanediol, 1,4-butanediol, and 1,6-hexanediol; the R2 source includes one or more of oxohexane, ethylene oxide, propylene oxide, and butylene oxide; the R3 source includes one or more of toluene or diphenylmethane; and the cyanate ester compound includes methyl isocyanate.

[0016] According to some embodiments of this application, the molar ratio of the monohydric alcohol or the dihydric alcohol, the cyanate ester compound, the R3 source, and the R2 source is 1:(1.8-2.2):(1.8-2.2):(20-100).

[0017] According to some embodiments of this application, the method further includes adjusting the pH of the solution containing the dispersant to 7-9 using a pH adjuster. This reduces the probability of dispersant aggregation and improves the dispersing effect of the dispersant.

[0018] According to some embodiments of this application, the method satisfies one or more of the following conditions: dehydrating the monohydric alcohol or the dihydric alcohol and then mixing it with the cyanate ester compound and the first initiator; cooling the first product and then mixing it with the R3 source and the second initiator; cooling the second product and then mixing it with the R2 source and the third initiator. This increases the reaction rate.

[0019] According to some embodiments of this application, the method satisfies one or more of the following conditions: the mass percentage of the first initiator is 1%-3% based on the total mass of the cyanate ester compound; the mass percentage of the second initiator is 1%-3% based on the total mass of the R3 source; and the mass percentage of the third initiator is 1%-3% based on the total mass of the R2 source.

[0020] According to some embodiments of this application, the first initiator, the second initiator, and the third initiator each independently comprise one or more of sodium persulfate, ammonium persulfate, benzoyl peroxide, dodecyl peroxide, lauroyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, and tert-butyl hydroperoxide. This increases the reaction rate.

[0021] According to some embodiments of this application, the method satisfies one or more of the following conditions: the heating temperature is 60℃-90℃, and the heating time is 2.5h-3.5h; the first product is cooled to 40℃-60℃; and the second product is cooled to 25℃-35℃. This improves the yield of the dispersant.

[0022] A third aspect of this application provides a method for detecting magnetic foreign matter, comprising: mixing a positive electrode active material, a dispersant, and water to form a slurry, wherein the dispersant includes the dispersant provided in the first aspect of this application or a dispersant prepared by the method provided in the second aspect of this application; placing a magnetic component in the slurry, and adsorbing magnetic foreign matter in the slurry through the magnetic component; collecting the magnetic foreign matter on the magnetic component, and testing the content of the magnetic foreign matter. Therefore, using this dispersant to disperse the positive electrode active material in water can improve the dispersion effect of the positive electrode active material, reduce the probability of agglomeration of the positive electrode active material, eliminate the need for repeated extraction of magnetic foreign matter, improve the extraction efficiency of magnetic foreign matter, thereby improving detection efficiency and reducing detection costs. Simultaneously, using water instead of NMP as a solvent can reduce the harmful effects of NMP.

[0023] According to some embodiments of this application, the mass percentage of the positive electrode active material is 10%-30% based on the total mass of the positive electrode active material and the water. This reduces solvent usage and improves detection efficiency.

[0024] According to some embodiments of this application, the magnetic foreign matter includes one or more of Fe particles, Cr particles, Ni particles, Cu particles, and Zn particles.

[0025] According to some embodiments of this application, the dispersant accounts for 1.5%-5% of the mass of the water. Therefore, by keeping the content of the dispersant within the above range, the dispersion effect on the positive electrode active material can be improved.

[0026] According to some embodiments of this application, the slurry does not include N-methylpyrrolidone. This reduces the hazards of NMP and lowers detection costs.

[0027] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0028] Various other advantages and benefits will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. In the drawings:

[0029] Figure 1 This is a schematic diagram of the process for preparing a dispersant according to one embodiment of this application.

[0030] Figure 2 This is a schematic flowchart of a method for detecting magnetic foreign objects according to an embodiment of this application.

[0031] Figure 3 This is the infrared spectrum of the dispersant prepared in Example 1 of this application. Detailed Implementation

[0032] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.

[0033] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0034] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0035] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] Currently, judging from market trends, battery applications are becoming increasingly widespread. Batteries are not only used in energy storage systems such as hydropower, thermal power, wind power, and solar power plants, but also extensively in electric vehicles such as electric bicycles, electric motorcycles, and electric cars, as well as in military equipment and aerospace. With the continuous expansion of battery applications, market demand is also constantly increasing.

[0038] Batteries include positive electrode active materials. During the preparation of positive electrode active materials, magnetic foreign matter (such as Fe, Cr, Bi, etc.) is inevitably introduced. When metallic foreign matter is present at the positive electrode, different metal elements have different potentials during charging. The metal element at the positive electrode will be oxidized into an ionic state and migrate to the negative electrode before the active metal element (such as lithium). At the negative electrode, it will be reduced to a metallic state, forming a solid metal, which can be considered as metal dendrites composed of different elements. If the metal element content is too high, the dendrites will grow too large, increasing the risk of puncturing the separator and causing battery self-discharge. Therefore, detecting the content of magnetic foreign matter in the positive electrode active material is necessary. Related technologies use NMP as a solvent to disperse the positive electrode active material when testing its content, reducing the liquid-liquid and solid-liquid interfacial tension, making the surface of the positive electrode active material easier to wet, thereby improving the dispersion effect of the positive electrode active material in NMP and increasing the extraction rate of magnetic foreign matter. However, NMP has limited dispersing effect on positive electrode active materials as a solvent. The testing process requires multiple extractions of magnetic foreign matter from the positive electrode active material to achieve complete removal, making the process cumbersome and inefficient. Furthermore, NMP itself is toxic and poses certain hazards during use, and its post-processing requires specific qualifications.

[0039] This application proposes a dispersant that can directly disperse positive electrode active materials in water for testing the content of magnetic foreign matter. Specifically, the dispersant includes carbamate groups, a benzene ring structure, and polyether segments. The carbamate groups exhibit excellent anchoring effects on the positive electrode active materials. The large π bonds of the benzene ring in the dispersant can also form π-π bonds with the surface of the positive electrode active materials, further enhancing the anchoring effect of the dispersant. The polyether segments, as hydrophilic groups, can tightly bind with water molecules. The dispersant adsorbs the positive electrode active materials through the carbamate groups and the benzene ring structure, and then, through the hydrophilic polyether segments, the positive electrode active materials are uniformly dispersed in water. Due to electrostatic repulsion, the dispersant on the surface of the positive electrode active materials reduces the probability of agglomeration, thereby improving the dispersion effect of the positive electrode active materials in water and increasing the extraction efficiency of magnetic foreign matter. The testing process eliminates the need for repeated extraction of magnetic foreign matter, thus improving testing efficiency.

[0040] The dispersant proposed in this application can be used to test the content of magnetic foreign matter in the positive electrode active material of lithium-ion secondary batteries.

[0041] A first aspect of this application provides a dispersant comprising a compound of formula I:

[0042] Wherein, R1 includes hydrogen atoms or

[0043] R2 includes -(CH2) x -, 1≤x≤6, 10≤n≤50, R3

[0044] Including substituents containing benzene rings, m≥2.

[0045] The dispersant proposed in this application comprises carbamate groups, a benzene ring structure, and polyether segments. The carbamate groups exhibit excellent anchoring effects on the positive electrode active material, and the large π bonds of the benzene ring can form π-π bonds with the surface of the positive electrode active material, further enhancing the anchoring effect of the dispersant. The polyether segments, as hydrophilic groups, can tightly bind with water molecules. The dispersant adsorbs the positive electrode active material through the carbamate groups and the benzene ring structure, and then, through the hydrophilic polyether segments, uniformly disperses the positive electrode active material in water. Water can be directly used as a solvent to disperse the positive electrode active material, eliminating the need for NMP and reducing the harmful effects of NMP. Due to electrostatic repulsion, the dispersant on the surface of the positive electrode active material reduces the probability of aggregation in water, thereby improving the dispersion effect and extraction efficiency of magnetic foreign matter. This eliminates the need for repeated extraction of magnetic foreign matter during testing, thus improving testing efficiency and reducing testing costs.

[0046] As an example, x can be 1, 2, 3, 4, 5 or 6, or a range of any of the above values.

[0047] As an example, n can be 10, 15, 20, 25, 30, 35, 40, 45 or 50, or a range of any of the above values.

[0048] According to some embodiments of this application, m can be 2, 3, 4, 5, 6, 7, etc. According to some specific embodiments of this application, 2 ≤ m ≤ 6.

[0049] According to some embodiments of this application, R3 comprises one or both of benzyl or diphenylmethane. Therefore, the large π-bond of the benzene ring structure in R3 can form π-π bonds with the surface of the positive electrode active material, further enhancing the anchoring effect on the positive electrode active material. According to some specific embodiments of this application, R3 comprises benzyl.

[0050] According to some embodiments of this application, the dispersant includes: As an example, -C m H 2m - Can include -C2H4-, -C4H8-, or -C6H 12 Therefore, the dispersant has a BAB structure, with twice the number of anchoring groups in its molecular structure, which can further improve the anchoring effect. Simultaneously, both ends of the molecular structure have hydrophilic polyether segments, which can better disperse the positive electrode active material in water after anchoring it. The BAB structure can also form a V-shaped steric hindrance, further preventing the positive electrode active material from agglomerating in water, improving the dispersion effect of the positive electrode active material, and thus improving the extraction efficiency of magnetic foreign matter.

[0051] According to some specific embodiments of this application, the dispersant includes

[0052]

[0053] Therefore, the aforementioned dispersant has a BAB structure, containing twice the number of anchoring groups in its molecular structure, which can further improve the anchoring effect. Simultaneously, both ends of the molecular structure have hydrophilic polyether segments, which can better disperse the positive electrode active material in water after anchoring it. The BAB structure can also form a V-shaped steric hindrance, further preventing the positive electrode active material from agglomerating in water, improving the dispersion effect of the positive electrode active material, and thus improving the extraction efficiency of magnetic foreign matter.

[0054] The second aspect of this application provides a method for preparing the dispersant provided in the first aspect of this application, comprising: dehydrating a monohydric alcohol or dihydric alcohol and mixing it with a cyanate ester compound, then heating the mixture to obtain a first product; cooling the first product and mixing it with an R3 source, reacting the mixture to obtain a second product, wherein the R3 source includes an aromatic hydrocarbon; cooling the second product and mixing it with an R2 source, reacting the mixture to obtain the dispersant, wherein the R2 source includes an epoxy compound. Thus, the dispersant prepared by this method possesses all the features and advantages of the dispersant provided in the first aspect of this application, which will not be elaborated further here. In summary, the dispersant prepared by this method can improve the uniformity of dispersion of positive electrode active materials in water, improve the extraction efficiency of magnetic foreign matter, improve the testing efficiency of magnetic foreign matter, and reduce testing costs.

[0055] The following provides a detailed explanation of each step of the method. (Refer to...) Figure 1 The method includes:

[0056] S10: Dehydrate a monohydric alcohol or dihydric alcohol and mix it with a cyanate ester compound, then heat the mixture to obtain the first product.

[0057] According to some embodiments of this application, the monohydric alcohol includes one or more of ethanol, propanol, butanol, and hexanol; the dihydric alcohol includes one or more of 1,2-propanediol, 1,4-butanediol, and 1,6-hexanediol.

[0058] Specifically, when a monohydric alcohol is dehydrated and then reacted with a cyanate ester compound, the resulting dispersant has an asymmetric structure; when a dihydric alcohol is dehydrated and then reacted with a cyanate ester compound, the resulting dispersant has a BAB structure.

[0059] According to some embodiments of this application, a monohydric alcohol or a dihydric alcohol is dehydrated under vacuum. Specifically, the monohydric alcohol or a dihydric alcohol is heated to 90°C-110°C and dehydrated under vacuum for 20-30 minutes.

[0060] As an example, a monohydric alcohol or a dihydric alcohol can be heated to 90°C, 95°C, 100°C, 105°C, or 110°C, or a range of any of the above values.

[0061] As an example, the vacuum dehydration time can be 20 min, 22 min, 24 min, 26 min, 28 min or 30 min, or a range of any of the above values.

[0062] According to some embodiments of this application, the heating temperature can be 60℃-90℃, for example, it can be 60℃, 70℃, 80℃ or 90℃, or it can be any range of the above values.

[0063] According to some embodiments of this application, the heating time can be 2.5h-3.5h, for example, it can be 2.5h, 2.7h, 2.9h, 3.1h, 3.3h or 3.5h, or it can be a range of any of the above values.

[0064] According to some embodiments of this application, the molar ratio of monohydric alcohol or dihydric alcohol to cyanate ester is 1:(1.8-2.2). That is, the molar ratio of monohydric alcohol to cyanate ester is 1:(1.8-2.2), and the molar ratio of dihydric alcohol to cyanate ester is 1:(1.8-2.2).

[0065] According to some embodiments of this application, the method may further include dehydrating the monohydric alcohol or the dihydric alcohol and mixing it with the cyanate ester compound and a first initiator, followed by heating to obtain a first product. This increases the reaction rate and makes the reaction more complete.

[0066] According to some embodiments of this application, based on the total mass of the cyanate ester compounds, the mass percentage of the first initiator can be 1%-3%, for example, it can be 1%, 1.5%, 2%, 2.5%, or 3%, or any range of the above values. This increases the reaction rate and makes the reaction more complete.

[0067] As an example, the first initiator includes one or more of sodium persulfate, ammonium persulfate, benzoyl peroxide, dodecyl peroxide, lauroyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, and tert-butyl hydroperoxide.

[0068] S20: After cooling the first product, mix it with the R3 source and react to obtain the second product.

[0069] According to some embodiments of this application, the R3 source includes aromatic hydrocarbons.

[0070] According to some embodiments of this application, the R3 source may include one or more of toluene or diphenylmethane.

[0071] According to some embodiments of this application, the temperature of the first product after cooling can be 40°C-60°C, for example, it can be 40°C, 45°C, 50°C, 55°C or 60°C, or it can be any range of the above values.

[0072] According to some embodiments of this application, the method may further include cooling the first product and then mixing it with the R3 source and the second initiator. This increases the reaction rate and allows the reaction to proceed more completely.

[0073] According to some embodiments of this application, based on the total mass of the R3 source, the mass percentage of the second initiator is 1%-3%, for example, it can be 1%, 1.5%, 2%, 2.5%, or 3%, or any range of the above values. This increases the reaction rate and makes the reaction more complete.

[0074] As an example, the second initiator may include one or more of sodium persulfate, ammonium persulfate, benzoyl peroxide, dodecyl peroxide, lauroyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, and tert-butyl hydroperoxide.

[0075] According to some embodiments of this application, the molar ratio of monohydric alcohol or dihydric alcohol, cyanate ester compound, and R3 source is 1:(1.8-2.2):(1.8-2.2). That is, the molar ratio of monohydric alcohol, cyanate ester compound, and R3 source is 1:(1.8-2.2):(1.8-2.2), and the molar ratio of dihydric alcohol, cyanate ester compound, and R3 source is 1:(1.8-2.2):(1.8-2.2).

[0076] S30: Cool the second product and mix it with the R2 source.

[0077] According to some embodiments of this application, the temperature of the second product after cooling can be 25°C-35°C, for example, it can be 25°C, 27°C, 29°C, 31°C, 33°C or 35°C, or it can be any range of the above values.

[0078] According to some embodiments of this application, the method may further include cooling the second product and then mixing it with the R2 source and the third initiator. This increases the reaction rate and allows the reaction to proceed more completely.

[0079] According to some embodiments of this application, the R2 source includes an epoxy compound.

[0080] According to some embodiments of this application, the R2 source includes one or more of oxohexane, ethylene oxide, propylene oxide, and butane oxide.

[0081] As an example, the third initiator may include one or more of sodium persulfate, ammonium persulfate, benzoyl peroxide, dodecyl peroxide, lauroyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, and tert-butyl hydroperoxide.

[0082] According to some embodiments of this application, based on the total mass of the R2 source, the mass percentage of the third initiator is 1%-3%, for example, it can be 1%, 1.5%, 2%, 2.5%, or 3%, or any range of the above values. This increases the reaction rate and makes the reaction more complete.

[0083] According to some embodiments of this application, the molar ratio of the monohydric alcohol or the dihydric alcohol, the cyanate ester compound, the R3 source, and the R2 source is 1:(1.8-2.2):(1.8-2.2):(20-100). That is, the molar ratio of the monohydric alcohol, the cyanate ester compound, the R3 source, and the R2 source is 1:(1.8-2.2):(1.8-2.2):(20-100), and the molar ratio of the dihydric alcohol, the cyanate ester compound, the R3 source, and the R2 source is 1:(1.8-2.2):(1.8-2.2):(20-100).

[0084] According to some embodiments of this application, the cyanate ester compound includes methyl isocyanate.

[0085] According to some embodiments of this application, the method may further include adjusting the pH of the solution containing the dispersant to 7-9 using a pH adjuster, for example, 7, 7.5, 8, 8.5, or 9, or any range of the above values. Specifically, sodium hydroxide may be added to neutralize the solution containing the dispersant.

[0086] A third aspect of this application provides a method for detecting magnetic foreign matter, comprising mixing a positive electrode active material, a dispersant, and water to form a slurry, wherein the dispersant includes the dispersant provided in the first aspect of this application or a dispersant prepared by the method provided in the second aspect of this application; placing a magnetic component in the slurry, and adsorbing magnetic foreign matter in the slurry through the magnetic component; collecting the magnetic foreign matter on the magnetic component, and testing the content of the magnetic foreign matter. Therefore, using this dispersant to disperse the positive electrode active material in water can improve the dispersion effect of the positive electrode active material, reduce the probability of aggregation of the positive electrode active material, eliminate the need for repeated extraction of magnetic foreign matter, improve the extraction efficiency of magnetic foreign matter, thereby improving detection efficiency and reducing detection costs. Simultaneously, using water instead of NMP as a solvent can reduce the harmful effects of NMP.

[0087] The following provides a detailed explanation of each step of the method. (Refer to...) Figure 2 The method includes:

[0088] S40: Mixing positive electrode active material, dispersant, and water to form a slurry.

[0089] According to some embodiments of this application, the positive electrode active material, the dispersant, and the water are mixed to form the slurry. The dispersant comprises carbamate groups, a benzene ring structure, and polyether segments. The carbamate groups have excellent anchoring effects on the positive electrode active material, and the large π bonds of the benzene ring in the dispersant can form π-π bonds with the surface of the positive electrode active material, further enhancing the anchoring effect of the dispersant. The polyether segments, as hydrophilic groups, can tightly bind with water molecules. The dispersant adsorbs the positive electrode active material through the carbamate groups and the benzene ring structure, and then, through the hydrophilic polyether segments, the positive electrode active material is uniformly dispersed in water. Due to electrostatic repulsion, the dispersant on the surface of the positive electrode active material reduces the probability of the positive electrode active material agglomerating, thereby improving the dispersion effect of the positive electrode active material in water and increasing the extraction efficiency of magnetic foreign matter. This eliminates the need for repeated extraction of magnetic foreign matter during testing, thus improving testing efficiency.

[0090] According to some embodiments of this application, based on the total mass of the positive electrode active material and the water, the mass percentage of the positive electrode active material is 10%-30%, for example, it can be 10%, 15%, 20%, 25%, or 30%, or any range of the above values. Therefore, since the slurry contains the above-mentioned dispersant, the probability of agglomeration of the positive electrode active material in water can be reduced while increasing the content of the positive electrode active material in the slurry, thereby improving testing efficiency, reducing solvent usage, and lowering testing costs.

[0091] According to some embodiments of this application, the dispersant accounts for 1.5%-5% of the mass of the water. For example, it can be 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%, or any range of the above values. Therefore, by keeping the content of the dispersant within the above range, the dispersion effect on the positive electrode active material can be improved.

[0092] According to some embodiments of this application, the slurry does not include N-methylpyrrolidone. Therefore, by using only water as a solvent and adding a dispersant to the water, the positive electrode active material can be uniformly dispersed in the water.

[0093] S50: Place the magnetic component into the slurry, and use the magnetic component to attract magnetic foreign objects in the slurry.

[0094] According to some embodiments of this application, the magnetic foreign matter includes one or more of Fe particles, Cr particles, Ni particles, Cu particles, and Zn particles.

[0095] According to some embodiments of this application, the magnetic component may include a magnetic rod and a heat-shrink tubing, the heat-shrink tubing covering the surface of the magnetic rod. The magnetic component adsorbs magnetic foreign objects through its cyclic movement within the slurry.

[0096] According to some embodiments of this application, the magnetic component can be moved in the slurry by a roller device, and the adsorption time can be 10 min to 20 min, for example, 10 min, 12 min, 14 min, 16 min, 18 min or 20 min, or any range of the above values.

[0097] Therefore, the presence of dispersants can improve the dispersion of positive electrode active materials in water, increase the extraction efficiency of magnetic foreign matter, reduce the number of times magnetic foreign matter in the positive electrode active materials is repeatedly adsorbed, simplify the testing process, and improve testing efficiency.

[0098] S60: Collect the magnetic foreign matter on the magnetic component and test the content of the magnetic foreign matter.

[0099] According to some embodiments of this application, the magnetic component with the adsorbed magnetic foreign matter is transferred into a container, the heat shrink tubing is separated from the magnetic rod, and the extracted magnetic foreign matter is rinsed using a rinsing bottle. During rinsing, a magnetic block is placed at the bottom of the container to adsorb the magnetic material and prevent its loss. A vacuum filtration device is used to transfer the magnetic foreign matter onto a filter membrane, the filter membrane is dried, and then transferred to a substrate. The membrane is then scanned using an optical instrument to detect the quantity of the magnetic foreign matter.

[0100] The method for detecting magnetic foreign matter content proposed in this application reduces the time for magnetic components to adsorb magnetic foreign matter in the slurry due to the good dispersion effect of the dispersant on the positive electrode active material. The testing time for magnetic foreign matter in a single batch of positive electrode active material is shortened by 20%, reducing time costs. At the same time, the presence of the dispersant can increase the solid content and viscosity of the slurry, reducing the amount of solvent used and lowering material costs.

[0101] According to some embodiments of this application, the type of positive electrode active material is not particularly limited.

[0102] According to some embodiments of this application, the positive electrode active material may be a known positive electrode active material for lithium-ion batteries. As an example, the positive electrode active material may include one or more of the following materials: lithium phosphates with an olivine structure, lithium transition metal oxides, and their respective modified compounds. Examples of lithium transition metal oxides may include, but are not limited to, lithium cobalt oxides (such as LiCoO2), lithium nickel oxides (such as LiNiO2), lithium manganese oxides (such as LiMnO2, LiMn2O4), lithium nickel cobalt oxides, lithium manganese cobalt oxides, lithium nickel manganese oxides, and lithium nickel cobalt manganese oxides (such as LiNiO2). 1 / 3 Co 1 / 3Mn 1 / 3 O2 (also known as NCM) 333 LiNi 0.5 Co 0.2 Mn 0.3 O2 (also known as NCM) 523 LiNi 0.5 Co 0.25 Mn 0.25 O2 (also known as NCM) 211 LiNi 0.6 Co 0.2 Mn 0.2 O2 (also known as NCM) 622 LiNi 0.8 Co 0.1 Mn 0.1 O2 (also known as NCM) 811 ), lithium nickel cobalt aluminum oxide (such as LiNi) 0.8 Co 0.15 Al 0.05 One or more of O2 and its modified compounds. Examples of lithium phosphates with an olivine structure include, but are not limited to, lithium iron phosphate (such as LiFePO4 (also known as LFP)), lithium manganese phosphate (such as LiMnPO4), and lithium manganese iron phosphate.

[0103] To make the technical problems, technical solutions, and beneficial effects solved by the embodiments of this application clearer, the following will provide a more detailed description in conjunction with the embodiments and accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit this application or its applications. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0104] Example 1

[0105] 1. Preparation of dispersants

[0106] (1) Ethylene glycol was dehydrated under vacuum at 100°C for 25 min;

[0107] (2) Cool to 30°C, add methyl isocyanate and benzoyl peroxide. The amount of benzoyl peroxide added is 2% based on the total mass of methyl isocyanate. Control the heating temperature at 75°C, react for 3 hours, and rotate at 200 r / min. The first product is obtained after the reaction.

[0108] (3) Cool the first product to 50°C, add toluene and benzoyl peroxide. The amount of benzoyl peroxide added is 2% based on the total mass of toluene. The reaction time is 2h. The second product is obtained after the reaction.

[0109] (4) Cool the second product to 30°C, add oxohexane and benzoyl peroxide and react for 3 hours at a speed of 400 r / min. The molar ratio of ethylene glycol, methyl isocyanate, toluene and oxohexane is 1:2:2:36. The amount of benzoyl peroxide added is 2% based on the total mass of oxohexane.

[0110] (5) Neutralize to pH 8 with sodium hydroxide, add measured distilled water for high-speed shear emulsification, and distill under reduced pressure to obtain...

[0111]

[0112] 2. Detection of magnetic foreign matter in positive electrode active material

[0113] (1) Weigh 2.69 kg of lithium iron phosphate and 150 g of the above dispersant and add them to 5 kg of water for premixing;

[0114] (2) The magnetic rod covered with heat shrink tubing is put into the slurry, the slurry is mixed evenly using a rotating device, and the magnetic rod is moved in a circular motion within the slurry to adsorb magnetic materials.

[0115] (3) Transfer the magnetic rod to a clean solvent container, separate the magnetic rod from the heat shrink tubing, collect the magnetic foreign matter on the heat shrink tubing into a beaker, and use a rinsing bottle to rinse the extracted material to remove the entrained slurry. During the rinsing process, use a magnetic block at the bottom of the beaker to attract the magnetic foreign matter and prevent it from escaping during the rinsing process.

[0116] (4) Use a vacuum filter to transfer the magnetic foreign matter onto the filter membrane, dry the filter membrane, transfer the filter membrane onto the substrate, and use an optical scanner to scan together to identify the number of magnetic foreign matter and obtain the number of the first extracted metallic magnetic foreign matter.

[0117] (5) The slurry extracted in step (2) is subjected to a second and a third extraction to obtain the number of metallic magnetic foreign objects extracted in the second extraction and the number of metallic magnetic foreign objects extracted in the third extraction, respectively.

[0118] Comparative Example 1

[0119] (1) Weigh 1.25 kg of lithium iron phosphate positive electrode active material and add it to 5 kg of NMP solvent for premixing;

[0120] (2) The magnetic rod covered with heat shrink tubing is put into the slurry, the slurry is mixed evenly using a rotating device, and the magnetic rod is moved in a circular motion within the slurry to adsorb magnetic materials.

[0121] (3) Transfer the magnetic rod to a clean solvent container, separate the magnetic rod from the heat shrink tubing, collect the magnetic foreign matter on the heat shrink tubing into a beaker, and use a rinsing bottle to rinse the extracted material to remove the entrained slurry. During the rinsing process, use a magnetic block at the bottom of the beaker to attract the magnetic foreign matter and prevent it from escaping during the rinsing process.

[0122] (4) Use a vacuum filter to transfer the magnetic foreign matter onto the filter membrane, dry the filter membrane, transfer the filter membrane onto the substrate, and use an optical scanner to scan together to identify the number of magnetic foreign matter and obtain the number of the first extracted metallic magnetic foreign matter.

[0123] (5) The slurry extracted in step (2) is subjected to a second and a third extraction to obtain the number of metallic magnetic foreign objects extracted in the second extraction and the number of metallic magnetic foreign objects extracted in the third extraction, respectively.

[0124] Comparative Example 2

[0125] (1) Weigh 1.25 kg of lithium iron phosphate and 150 g of dispersant PEG4000 (polyethylene glycol 4000) and add them to 5 kg of water for premixing;

[0126] (2) The magnetic rod covered with heat shrink tubing is put into the slurry, the slurry is mixed evenly using a rotating device, and the magnetic rod is moved in a circular motion within the slurry to adsorb magnetic materials.

[0127] (3) Transfer the magnetic rod to a clean solvent container, separate the magnetic rod from the heat shrink tubing, collect the magnetic foreign matter on the heat shrink tubing into a beaker, and use a rinsing bottle to rinse the extracted material to remove the entrained slurry. During the rinsing process, use a magnetic block at the bottom of the beaker to attract the magnetic foreign matter and prevent it from escaping during the rinsing process.

[0128] (4) Use a vacuum filter to transfer the magnetic foreign matter onto the filter membrane, dry the filter membrane, transfer the filter membrane onto the substrate, and use an optical scanning instrument to scan it to identify the number of magnetic foreign matter and obtain the number of the first extracted metallic magnetic foreign matter.

[0129] (5) The slurry extracted in step (2) is subjected to a second and a third extraction to obtain the number of metallic magnetic foreign objects extracted in the second extraction and the number of metallic magnetic foreign objects extracted in the third extraction, respectively.

[0130] The methods for detecting the content of magnetic foreign matter in the positive electrode active material in Examples 1-10 are the same as in Example 1, and the differences are detailed in Table 1.

[0131] Table 1

[0132]

[0133] Performance testing

[0134] 1. Specific calculation method for magnetic foreign matter content

[0135] Method for calculating the content of magnetic foreign matter extracted in a single scan: After the optical scanning instrument completes the scan, the content is calculated according to the following formula based on the scan results:

[0136] The impact of particles on the battery gradually increases with the increase of particle size. Therefore, this application only monitors the content of particles with a particle size of more than 25 μm in the positive electrode active material. Particles with a particle size of 25 μm-100 μm are regarded as one category, and particles with a particle size of more than 100 μm are regarded as another category. The following formula is used to calculate the cleanliness of the positive electrode active material by weighting.

[0137] Final result = Number of magnetic foreign matter particles (particle size between 25μm and 100μm) × 50% + Number of impurity particles (particle size ≥ 100μm)

[0138] 100μm)×100%

[0139] Table 2 shows the test results of Example 1. Taking Table 2 as an example: during the first extraction, the number of metal particles with a diameter of 25μm-100μm was 158 pcs, and the number of metal particles with a diameter of ≥100μm was 12 pcs; the number of magnetic foreign matter particles extracted in the first extraction...

[0140] =158×50%+12×100%=91pcs

[0141] The total number of magnetic foreign objects extracted in the three extractions = the number of magnetic foreign objects extracted in the first extraction + the number of magnetic foreign objects extracted in the second extraction + the number of magnetic foreign objects extracted in the third extraction.

[0142] First extraction rate = (Number of magnetic foreign objects extracted in the first extraction / Total number of magnetic foreign objects extracted in the three extractions)

[0143] ×100%.

[0144] The methods for detecting the content of magnetic foreign matter in each embodiment and comparative example are shown in Table 3. The content of magnetic foreign matter in the first extraction, the second extraction, the third extraction, the total number of extractions, and the first extraction rate are measured.

[0145] 2. Solid content of positive electrode active material in slurry

[0146] The content of positive electrode active material in the slurry = (mass of positive electrode active material / (mass of positive electrode active material + mass of solvent)) × 100%.

[0147] 3. Methods for identifying the structure of dispersants

[0148] The structure was identified using an infrared spectrometer.

[0149] Table 2

[0150] Particle size First extraction / pcs Second extraction / pcs Third extraction / pcs ≥100μm 12 7 3 50μm-100μm 54 16 12 25μm-50μm 104 34 14

[0151] Table 3

[0152]

[0153] in conclusion:

[0154] Depend on Figure 3 It can be seen that 2868.05cm -1 The peak at 1718.23 cm⁻¹ represents the stretching vibration of CH₃- and -CH₂-. -1 The peak value is the stretching vibration peak of C=O, at 1026.23 cm⁻¹. -1 The peak represents the stretching vibration of the COC bond, at 710.05 cm⁻¹. -1 The peak for the stretching vibration of -HNC=O is 848.19 cm⁻¹. -1 This is the stretching vibration peak of the benzene ring.

[0155] As can be seen from the comparison between Examples 1-10 and Comparative Examples 1 and 2, by adding the dispersant of this application to water, the first extraction rate of magnetic foreign matter content exceeds the effect of existing NMP extraction of magnetic foreign matter. This shows that the method proposed in this application can replace the existing NMP solvent to reduce the number of repeated extractions and improve testing efficiency. At the same time, replacing NMP solvent with water saves costs and reduces environmental impact.

[0156] As can be seen from the comparison between Examples 1-10 and Comparative Example 2, the extraction effect of magnetic foreign matter using the dispersant proposed in this application is significantly better than that of PEG4000 as a dispersant.

[0157] As can be seen from Examples 1-5, this application can increase the solid content of the positive electrode active material in the solvent by adding a dispersant to water, while maintaining a high extraction rate, thereby improving the efficiency of magnetic foreign matter detection.

[0158] As can be seen from Examples 6-9, this application can improve the extraction rate of magnetic foreign objects by adjusting the amount of dispersant, thereby improving the efficiency of magnetic foreign object detection.

[0159] As can be seen from Examples 1-10, this application can be used to detect the content of magnetic foreign matter in the positive electrode active material of lithium secondary batteries and the content of magnetic foreign matter in the positive electrode active material of sodium secondary batteries.

[0160] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Although this application 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 or all of the technical features therein. These modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application, and they should all be covered within the scope of the claims and specification of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any way. This application is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A dispersant, characterized in that, The dispersant comprises a compound represented by Formula I: Wherein, R1 includes hydrogen atoms or R2 includes -(CH2) x -, 1≤x≤6, 10≤n≤50, R3 includes substituents containing benzene rings, m≥2.

2. The dispersant according to claim 1, characterized in that, One or more of the following conditions must be met: 2≤m≤6； R3 includes one or both of benzyl or diphenylmethane.

3. The dispersant according to claim 1 or 2, characterized in that, The compounds represented by Formula I include:

4. The dispersant according to any one of claims 1-3, characterized in that, The compounds represented by Formula I include 5. A method for preparing the dispersant according to any one of claims 1-4, characterized in that, include: The monohydric alcohol or dihydric alcohol is dehydrated and then mixed with a cyanate ester compound, and heated to obtain the first product; The first product was cooled and mixed with an R3 source, and the reaction yielded a second product, wherein the R3 source included aromatic hydrocarbons. The second product is cooled and mixed with the R2 source. After the reaction, a dispersant of Formula I is obtained, wherein the R2 source includes an epoxy compound.

6. The method according to claim 5, characterized in that, One or more of the following conditions must be met: The monohydric alcohol includes one or more of ethanol, propanol, butanol, and hexanol; The diol includes one or more of 1,2-propanediol, 1,4-butanediol, and 1,6-hexanediol; The R2 source includes one or more of the following: oxohexane, ethylene oxide, propylene oxide, and butane oxide; R3 sources include one or more of toluene or diphenylmethane; The cyanate compounds include methyl isocyanate.

7. The method according to claim 5 or 6, characterized in that, The molar ratio of the monohydric alcohol or the dihydric alcohol, the cyanate ester compound, the R3 source, and the R2 source is 1:(1.8-2.2):(1.8-2.2):(20-100).

8. The method according to any one of claims 5-7, characterized in that, Also includes: The pH of the solution containing the dispersant is adjusted to 7-9 using a pH adjuster.

9. The method according to any one of claims 5-8, characterized in that, One or more of the following conditions must be met: The monohydric alcohol or the dihydric alcohol is dehydrated and then mixed with the cyanate ester compound and the first initiator; The first product is cooled and then mixed with the R3 source and the second initiator; The second product is cooled and then mixed with the R2 source and the third initiator.

10. The method according to claim 9, characterized in that, One or more of the following conditions must be met: Based on the total mass of the cyanate ester compounds, the mass percentage of the first initiator is 1%-3%; Based on the total mass of the R3 source, the mass percentage of the second initiator is 1%-3%; Based on the total mass of the R2 source, the mass percentage of the third initiator is 1%-3%.

11. The method according to claim 9 or 10, characterized in that, The first initiator, the second initiator, and the third initiator each independently comprise one or more of the following: sodium persulfate, ammonium persulfate, benzoyl peroxide, dodecyl peroxide, lauroyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, azobisisobutyronitrile, and tert-butyl hydroperoxide.

12. The method according to any one of claims 5-11, characterized in that, One or more of the following conditions must be met: The heating temperature is 60℃-90℃, and the heating time is 2.5h-3.5h; The first product was cooled to 40°C-60°C; The second product was cooled to 25°C-35°C.

13. A method for detecting the content of magnetic foreign matter, characterized in that, include: A slurry is formed by mixing a positive electrode active material, a dispersant, and water, wherein the dispersant includes the dispersant according to any one of claims 1-4 or the dispersant prepared by the method according to any one of claims 5-12; A magnetic component is placed inside the slurry, and magnetic foreign objects in the slurry are adsorbed by the magnetic component. Collect the magnetic foreign matter on the magnetic component and test the content of the magnetic foreign matter.

14. The method according to claim 13, characterized in that, Based on the total mass of the positive electrode active material and the water, the mass percentage of the positive electrode active material is 10%-30%.

15. The method according to claim 13 or 14, characterized in that, The magnetic foreign matter includes one or more of Fe particles, Cr particles, Ni particles, Cu particles, and Zn particles.

16. The method according to any one of claims 13-15, characterized in that, The dispersant has a mass ratio of 1.5% to 5% in the water.

17. The method according to any one of claims 13-16, characterized in that, The slurry does not include N-methylpyrrolidone.

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