Polymers, methods for their production, use, dispersant compositions, methods for their production, positive electrode slurries, positive electrode sheets, lithium ion batteries

Abstract

The application belongs to the technical field of lithium batteries, and specifically provides a polymer, a preparation method and use thereof, a dispersant composition and a preparation method thereof, a positive electrode slurry, a positive electrode sheet, and a lithium ion battery, aiming to solve the problem that existing small molecule alcohol amine as a positive electrode dispersant has no softening function and easily leads to cycle deterioration. To this end, the polymer of the application is a polymer containing a blocked isocyanate structure, a polyether structure and a polyester structure, and the blocked isocyanate structure is an isocyanate structure blocked by using a triazole. The polymer of the application is simultaneously applied to the positive electrode slurry as a dispersant together with small molecule alcohol amine, has excellent viscosity stabilization and softening effects, and will not cause battery cycle deterioration.

Description

Technical Field

[0001] This application belongs to the field of lithium battery technology, specifically providing a polymer and its preparation method, its uses, a dispersant composition and its preparation method, a positive electrode slurry, a positive electrode sheet, and a lithium-ion battery. Background Technology

[0002] As the capacity of lithium-ion batteries increases, the amount of positive electrode coating increases, requiring a reduction in the amount of positive electrode dispersant used while providing multiple functions.

[0003] Traditional dispersants are mainly divided into two categories. One category is represented by phosphate esters, which are added at the 0.1% level and have some flexibility-enhancing function but do not meet the dispersion requirements. The other category is represented by small-molecule amines, which are added at even lower levels, only at the 0.01% level, but have no flexibility-enhancing function and their small molecular structure easily leads to cycle degradation. It can be seen that traditional cathode dispersants cannot meet the current requirements for stabilizing adhesion, enhancing flexibility, and not deteriorating battery cycle performance.

[0004] Accordingly, a new technical solution is needed in this field to solve the above-mentioned technical problems. Summary of the Invention

[0005] This application aims to solve the above-mentioned technical problems, namely, to provide a polymer that can be used as a dispersant in combination with small molecule alcohol amines, so as to solve the problem that existing small molecule alcohol amines as positive electrode dispersants have no softening function and are prone to cycle deterioration.

[0006] In a first aspect, this application provides a polymer comprising a blocked isocyanate structure, a polyether structure, and a polyester structure, wherein the blocked isocyanate structure is an isocyanate structure blocked using triazole.

[0007] In a second aspect, this application provides a method for preparing a polymer, the method comprising: S1: providing a polyether segment and polyester segment block copolymer, wherein the polyester segments are hydroxyl-terminated; S2: reacting the polyether segment and polyester segment block copolymer with diisocyanate under the catalysis of stannous octoate to obtain an isocyanate-terminated polyether segment and polyester segment block copolymer; S3: reacting the isocyanate-terminated polyether segment and polyester segment block copolymer with triazole under the catalysis of stannous octoate, thereby blocking the isocyanate groups with triazole to obtain the polymer.

[0008] In a preferred embodiment of the above-mentioned method for preparing the polymer, in step S2, the diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; and / or, in step S2, the molar ratio of the block copolymer of the polyether and polyester to the diisocyanate is 1:1; and / or, in step S3, the molar ratio of the triazole to the diisocyanate in step S2 is (1~1.1):1; and / or, the reaction temperature in step S3 is 60~80℃.

[0009] In a preferred embodiment of the above-mentioned polymer preparation method, in step S2, the diisocyanate is isophorone diisocyanate.

[0010] In the preferred embodiment of the above-mentioned polymer preparation method, step S1 specifically includes: S11: ring-opening polymerization of alcohol and alkyl epoxide under the catalysis of DMC catalyst to obtain alcohol polyether; S12: reaction of the alcohol polyether with sodium hydride to obtain alkoxide; S13: ring-opening polymerization of the alkoxide and lactone monomer under the catalysis of stannous octoate, and adding acetic acid for end capping to obtain a block copolymer of polyether segment and polyester segment, wherein the polyester segment ends with hydroxyl groups.

[0011] In a preferred embodiment of the above-mentioned polymer preparation method, in step S11, the alcohol is a monohydroxy primary alcohol; and / or, in step S11, the epoxide is one or more of ethylene oxide and propylene oxide; and / or, in step S11, the molar ratio of alcohol to epoxide is alcohol:epoxide = 1:(100~150); and / or, in step S11, the DMC catalyst is 0.01%~0.1% of the total mass of the alcohol and the epoxide; and / or, in step S12, the alcohol polyether and the sodium hydride... The molar ratio is 1:1; and / or, in step S13, the molar ratio of the alkoxide to the lactone monomer is 1:1, and the molar ratio of the alkoxide to the acetic acid is 1:1; and / or, in step S13, the stannous octoate toluene solution is 0.1% to 0.3% of the total mass of the alcohol polyether and the lactone monomer, wherein the concentration of stannous octoate in the stannous octoate toluene solution is 0.1%; and / or, in step S13, the reaction temperature is 110 to 140°C; and / or, in step S13, the lactone monomer is ε-caprolactone.

[0012] In a preferred embodiment of the above-mentioned method for preparing the polymer, in step S11, the monohydroxy primary alcohol is benzyl alcohol; and / or, in step S11, the epoxide is ethylene oxide; and / or, in step S11, the DMC catalyst is 0.05% of the total mass of the alcohol and the epoxide.

[0013] In a third aspect, this application provides the use of the above-mentioned polymer or the polymer prepared by the above-mentioned polymer preparation method as a dispersant in the preparation of positive electrode slurry, together with small molecule alcoholamines.

[0014] In a fourth aspect, this application provides a dispersant composition comprising a small molecule alkanolamine and a polymer, wherein the small molecule alkanolamine is an alkanolamine with a molecular weight not greater than 200, and the polymer is the aforementioned polymer or a polymer prepared by the aforementioned polymer preparation method.

[0015] In a preferred embodiment of the above dispersant composition, the ratio of the total molar amount of hydroxyl and amino groups in the small molecule alkanolamine to the molar amount of the blocked isocyanate structure in the polymer is (amino group + hydroxyl group): polymer = (1~1.2): (1~1.2); and / or, the small molecule alkanolamine includes one or more of isopropanolamine, isobutanolamine, and n-butanolamine.

[0016] In a preferred embodiment of the above dispersant composition, the ratio of the total molar amount of hydroxyl and amino groups in the small molecule alkanolamine to the molar amount of the blocked isocyanate structure in the polymer is (amino group + hydroxyl group): polymer = (1~1.2):1; and / or, the small molecule alkanolamine includes isopropanolamine.

[0017] In a fifth aspect, this application provides a method for preparing a dispersant composition, the method comprising: mixing the polymer with a small molecule alcohol amine uniformly to obtain a dispersant composition.

[0018] In a sixth aspect, this application provides the use of the above-described dispersant composition as a positive electrode dispersant in the preparation of positive electrode slurry.

[0019] In a seventh aspect, this application provides a positive electrode slurry, the positive electrode slurry comprising a positive electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant is the above-mentioned dispersant composition or the dispersant is composed of the above-mentioned polymer or a polymer prepared by the above-mentioned polymer preparation method and a small molecule alkanolamine, wherein the small molecule alkanolamine is an alkanolamine with a molecular weight not greater than 200.

[0020] In an eighth aspect, this application provides a positive electrode sheet, the positive electrode sheet comprising a positive current collector and a positive active material layer located on the surface of the positive current collector, the positive active material layer being formed by coating the surface of the positive current collector with the aforementioned positive electrode slurry.

[0021] In a ninth aspect, this application provides a lithium-ion battery, the lithium-ion battery comprising the above-described positive electrode sheet.

[0022] Compared with the prior art, the polymer and dispersant composition of this application have the following beneficial effects:

[0023] The dispersant composition of this application includes a small molecule alkanolamine and a polymer, wherein the polymer is a polymer containing a blocked isocyanate structure, a polyether structure and a polyester structure, and the blocked isocyanate structure is an isocyanate structure blocked by triazole. The small molecule alkanolamine and the polymer are used as dispersants (i.e. the dispersant composition of this application) in the positive electrode slurry, which have excellent stabilizing and softening effects, and can remove the small molecule alkanolamine by reaction during the preparation of the positive electrode sheet, so that it will not be introduced into the battery and thus will not cause battery cycle deterioration.

[0024] Specifically, small-molecule alkanolamines, due to their large molar number of amino and hydroxyl groups, provide sufficient anchoring sites, enabling them to fully contact the powder. Furthermore, the charge repulsion of the amino groups prevents agglomeration, thus improving adhesion stability. The polyether polyester structure in the polymer has low rotational steric hindrance, and the ether bonds are less likely to form strong hydrogen bonds. The disordered structure formed by copolymerization can suppress excessive crystallization and lower the overall glass transition temperature, resulting in excellent softening effects. The triazole blocking of isocyanate groups prevents the isocyanate groups from reacting with hydroxyl and amino groups before coating and baking. This blocking is a reversible reaction, and the blocking occurs via urea bonds. After being heated and desealed, it reverts to isocyanate and triazole. The desealed isocyanate can react with the amine and hydroxyl groups in the small molecule alkanolamine to generate urea bonds and urethane bonds, respectively, which are the functional groups of polyurethane and polyurea. The functional groups of polyurethane and polyurea can improve the flexibility of the positive electrode and prevent cracking. In addition, it can improve the electrolyte resistance to a certain extent and improve the cycle performance of the battery. Furthermore, it has low activity under high potential environment of the positive electrode, so it will not cause cycle deterioration. Moreover, the small molecule of triazole is a five-membered aromatic heterocycle with excellent electrochemical stability, which also will not cause cycle deterioration. Attached Figure Description

[0025] The preferred embodiments of this application are described below with reference to the accompanying drawings, in which:

[0026] Figure 1 This is a flowchart of the main steps of the method for preparing the polymer of this application;

[0027] Figure 2 This is a flowchart illustrating an embodiment of the polymer preparation method of this application;

[0028] Figure 3 This is the infrared spectrum of the polymer in Example 1 of this application when it is not heated;

[0029] Figure 4 This is the infrared spectrum of the polymer in Example 1 of this application after baking at 80°C for half an hour;

[0030] Figure 5This is the infrared spectrum of the dispersant composition of Example 1 of this application after baking at 80°C for half an hour. Detailed Implementation

[0031] Preferred embodiments of this application will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of this application and are not intended to limit the scope of protection of this application.

[0032] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0033] In this application, "at least one" means one or more, and "more than one" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, "at least one of a, b, or c", or "at least one of a, b, and c", can both mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple.

[0034] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0035] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0036] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass described in the embodiments of this application can be a mass unit known in the chemical industry, such as μg, mg, g, or kg.

[0037] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, "first XX" may also be referred to as "second XX," and similarly, "second XX" may also be referred to as "first XX." Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0038] Unless otherwise specified, the experimental methods used in the following examples are conventional methods, and the materials and reagents used in the following examples are commercially available unless otherwise specified.

[0039] As pointed out in the background art, existing small molecule alcohol amines, as positive electrode dispersants, have no softening function and are prone to causing cycle deterioration.

[0040] This application provides a dispersant composition comprising a small molecule alkanolamine and a polymer, wherein the polymer is a polymer containing a blocked isocyanate structure, a polyether structure, and a polyester structure, and the blocked isocyanate structure is an isocyanate structure blocked by triazole; the dispersant composition is used as a dispersant by polymer compounding, and when applied to a positive electrode slurry, it has excellent adhesion stabilization and flexibility effects, and does not cause battery cycle degradation.

[0041] In a first aspect, this application provides a polymer containing a blocked isocyanate structure, a polyether structure, and a polyester structure, wherein the blocked isocyanate structure is an isocyanate structure blocked using triazole.

[0042] The polyether polyester structure in this application exhibits low rotational steric hindrance, and the ether bonds are less prone to forming strong hydrogen bonds. The disordered structure formed by copolymerization can suppress excessive crystallization and reduce the overall glass transition temperature, resulting in excellent softening effects. The triazole blocking of the isocyanate groups prevents the isocyanate groups from reacting with hydroxyl and amine groups before coating and baking. This blocking is a reversible reaction; the blocking occurs as urea bonds, and heating deblocks the bonds, restoring them to isocyanate and triazole. Therefore, when this polymer is used in combination with small-molecule alkanolamines as a dispersant, the small-molecule alkanolamines act as the positive electrode in the slurry stage. The material provides stable adhesion properties. During the heating process of preparing the positive electrode sheet, the small molecule alkanolamine reacts with the unsealed isocyanate. The amine and hydroxyl groups in the small molecule alkanolamine react with the isocyanate to form urea bonds and urethane bonds, respectively. These are the functional groups of polyurethane and polyurea, which can improve the flexibility of the positive electrode sheet and prevent cracking. This ensures that there are no more small molecule alkanolamines in the positive electrode sheet and the battery, thus preventing cycle deterioration of the battery. Furthermore, the triazole small molecule is a five-membered aromatic heterocycle with excellent electrochemical stability, which also does not cause cycle deterioration, thereby improving the cycle performance of the battery.

[0043] In a second aspect, this application provides a method for preparing a polymer, used to prepare the polymer provided in the first aspect.

[0044] Specifically, please refer to Figure 1 The preparation method of the polymer of this application includes the following steps: S1: Providing a polyether segment and polyester segment block copolymer, wherein the polyester segments are hydroxyl-terminated; specifically, the polyether segment and polyester segment block copolymer can be purchased or prepared in-house. S2: Reacting the polyether segment and polyester segment block copolymer with diisocyanate under the catalysis of stannous octoate to obtain an isocyanate-terminated polyether segment and polyester segment block copolymer. S3: Reacting the isocyanate-terminated polyether segment and polyester segment block copolymer with triazole under the catalysis of stannous octoate, so that the triazole blocks the isocyanate groups to obtain the polymer.

[0045] Preferably, in step S2, the diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate.

[0046] In some preferred embodiments, in step S2, the diisocyanate is isophorone diisocyanate. Isophorone diisocyanate has a moderate reaction rate and is more convenient to use.

[0047] Preferably, in step S2, the molar ratio of the polyether segment to the polyester segment block copolymer to the diisocyanate is 1:1.

[0048] Preferably, the molar ratio of triazole in step S3 to diisocyanate in step S2 is (1~1.1):1. Triazole is kept in excess to block each isocyanate segment in the isocyanate-terminated polyether segment and the polyester block copolymer, avoiding the presence of free isocyanate in the system and thus preventing the consumption of small molecule alkanolamines in the dispersant composition.

[0049] Preferably, the reaction temperature in step S3 is 60~80℃.

[0050] Preferably, please refer to Figure 2 Step S1 specifically includes: S11: Ring-opening polymerization of alcohol and alkylene oxide under the catalysis of DMC catalyst to obtain alcohol polyether. S12: Reaction of alcohol polyether with sodium hydride to obtain alkoxide. S13: Ring-opening polymerization of alkoxide and lactone monomer under the catalysis of stannous octoate, and end-capping with acetic acid to obtain a block copolymer of polyether segments and polyester segments, wherein the polyester segments are terminally hydroxyl groups.

[0051] Preferably, in step S11, the alcohol is a monohydroxy primary alcohol.

[0052] Specifically, monohydroxy primary alcohols can be aliphatic primary alcohols, aromatic primary alcohols, or primary alcohols containing ether bonds.

[0053] Aliphatic primary alcohols include short-chain alkyl alcohols (e.g., methanol, ethanol, propanol, butanol (n-butanol, isobutanol), pentanol, hexanol, etc.), long-chain alkyl alcohols (e.g., lauryl alcohol (dodecyl alcohol), myristyl alcohol (tetradecyl alcohol), cetyl alcohol (hexadecyl alcohol), stearyl alcohol (octadecyl alcohol), oleyl alcohol (unsaturated), behenyl alcohol (dodecyl alcohol), etc.), and branched-chain alkyl alcohols (e.g., 2-ethylhexanol, isodecanol, isothietol, guerbert alcohol, etc.).

[0054] Aromatic primary alcohols include benzyl alcohol, p-methylbenzyl alcohol, p-chlorobenzyl alcohol, and phenethyl alcohol.

[0055] Primary alcohols containing ether bonds include alkyl-terminated polyethylene glycol monoethers (e.g., methoxy polyethylene glycol, ethoxy polyethylene glycol, butoxy polyethylene glycol) and alkylphenol polyoxyethylene ether monoethers (e.g., octylphenol polyoxyethylene ether (C8H)). 17 -C6H4-O-(CH2CH2O)nH), nonylphenol polyoxyethylene ether (C9H 19 -C6H4-O-(CH2CH2O)nH, etc.

[0056] In some preferred embodiments, in step S11, the alcohol is benzyl alcohol. Choosing benzyl alcohol has several advantages: first, the benzene ring enhances the activity of the hydroxyl group, which is beneficial for the reaction; second, its low molecular weight has minimal impact on the molecular weight of the final synthesized product; and third, benzyl alcohol is a mature chemical raw material with low cost.

[0057] Preferably, in step S11, the epoxide is one or more of ethylene oxide and propylene oxide.

[0058] In some preferred embodiments, in step S11, the epoxide is ethylene oxide.

[0059] Preferably, in step S11, the molar ratio of alcohol to alkyl oxide is alcohol:alkyl oxide = 1:(100~150).

[0060] Preferably, in step S11, the DMC catalyst is 0.01% to 0.1% of the total mass of the alcohol and epoxide.

[0061] In some preferred embodiments, in step S11, the DMC catalyst is 0.05% of the total mass of the alcohol and epoxide.

[0062] Preferably, in step S11, the DMC catalyst comprises Co-Zn DMC (cobalt-zinc bimetallic cyanide).

[0063] Preferably, in step S12, the molar ratio of alcohol polyether to sodium hydride is 1:1.

[0064] Preferably, in step S13, the molar ratio of alkoxide to lactone monomer is 1:1, and the molar ratio of alkoxide to acetic acid is 1:1.

[0065] Preferably, in step S13, the stannous octoate toluene solution is 0.1% to 0.3% of the total mass of the alcohol polyether and lactone monomer, wherein the concentration of stannous octoate in the stannous octoate toluene solution is 0.1%.

[0066] Preferably, in step S13, the reaction temperature is 110~140℃.

[0067] Preferably, in step S13, the lactone monomer is ε-caprolactone.

[0068] In a third aspect, this application provides the use of the polymer provided in the first aspect and the small molecule amine as dispersants in the preparation of positive electrode slurry.

[0069] In a fourth aspect, this application provides a dispersant composition comprising a small molecule alkanolamine and a polymer, wherein the small molecule alkanolamine is an alkanolamine with a molecular weight not greater than 200, and the polymer is the polymer provided in the first aspect or a polymer prepared by the method for preparing the polymer provided in the second aspect.

[0070] The dispersant composition of this application, when applied to the positive electrode slurry, exhibits excellent stabilizing and softening properties, and does not cause battery cycle degradation.

[0071] Specifically, small-molecule alkanolamines, due to their large molar number of amino and hydroxyl groups, provide sufficient anchoring sites, enabling them to fully contact the powder. Furthermore, the charge repulsion of the amino groups prevents agglomeration, thus improving adhesion stability. The polyether polyester structure in the polymer has low rotational steric hindrance, and the ether bonds are less likely to form strong hydrogen bonds. The disordered structure formed by copolymerization can suppress excessive crystallization and lower the overall glass transition temperature, resulting in excellent softening effects. Triazole blocking of the isocyanate groups prevents the isocyanate groups from reacting with hydroxyl and amino groups before coating and baking. This blocking is a reversible reaction; during blocking, urea bonds are present, and the blocking is deblocked upon heating. The solution is restored to isocyanate and triazole. The unsealed isocyanate reacts with the amine and hydroxyl groups in the small molecule alkanolamine to form urea bonds and urethane bonds, respectively. These are the functional groups of polyurethane and polyurea, which can improve the flexibility of the positive electrode and prevent cracking. In addition, it can improve the electrolyte resistance and enhance the cycle performance of the battery. Furthermore, by heating, the small molecule alkanolamine reacts with the isocyanate groups and is removed. The small molecule alkanolamine is no longer present in the positive electrode and is not introduced into the battery, thus preventing cycle degradation. Moreover, the triazole small molecule is a five-membered aromatic heterocycle with excellent electrochemical stability, which also does not cause cycle degradation.

[0072] Preferably, in the dispersant composition, the ratio of the total molar amount of hydroxyl and amino groups in the small molecule alkanolamine to the molar amount of the blocked isocyanate structure in the polymer is (amino group + hydroxyl group): polymer = (1~1.2): (1~1.2).

[0073] Specifically, the ratio of (amine group + hydroxyl group) to polymer can be 1:1, 1:1.1, 1:1.2, 1.1:1, 1.2:1, or any two of the above ratios.

[0074] In some preferred embodiments, in the dispersant composition, the ratio of the total molar amount of hydroxyl and amino groups in the small molecule alkanolamine to the molar amount of the blocked isocyanate structure in the polymer is (amino group + hydroxyl group): polymer = (1~1.2):1.

[0075] Specifically, the ratio of (amine group + hydroxyl group) to polymer can be 1:1, 1.05:1, 1.1:1, 1.15:1, 1.2:1, or any two of the above ratios.

[0076] Preferably, the small molecule alcoholamine includes one or more of isopropanolamine, isobutanolamine, and n-butanolamine.

[0077] In some implementations, the small molecule alcohol amine is isopropanolamine.

[0078] In some other embodiments, the small molecule amine is isobutanolamine.

[0079] In some other embodiments, the small molecule alcohol amine is n-butanolamine.

[0080] In a fifth aspect, this application provides a method for preparing a dispersant composition for preparing the dispersant composition provided in the fourth aspect.

[0081] Specifically, the method for preparing the dispersant composition of this application includes mixing a polymer with a small molecule alcohol amine to obtain a dispersant composition.

[0082] In a sixth aspect, this application provides the use of the dispersant composition of the fourth aspect as a positive dispersant in the preparation of positive electrode slurry.

[0083] In a seventh aspect, this application provides a positive electrode slurry, which includes a positive electrode active material, a conductive agent, a binder, and a dispersant. The dispersant is a dispersant composition of the fourth aspect or is composed of a polymer of the first aspect and a small molecule alkanolamine, wherein the small molecule alkanolamine has a molecular weight of not more than 200.

[0084] In the preparation of positive electrode slurry, small molecule alkanolamines and polymers can be added to the slurry separately, or the small molecule alkanolamines and polymers can be mixed into a dispersant composition before being added to the slurry.

[0085] In an eighth aspect, this application provides a positive electrode sheet, which includes a positive current collector and a positive active material layer located on the surface of the positive current collector, wherein the positive active material layer is formed by coating the surface of the positive current collector with the positive electrode slurry of the seventh aspect.

[0086] In the ninth aspect, a lithium-ion battery is provided, which includes the positive electrode provided in the eighth aspect.

[0087] The dispersant composition of this application and its beneficial effects will be described in detail below through several specific embodiments and test examples.

[0088] Example 1

[0089] The dispersant composition of this embodiment is prepared by the following steps:

[0090] (1) To prepare alcohol polyether by ring-opening polymerization of alcohol and ethylene oxide (EO) under the catalysis of DMC catalyst: benzyl alcohol and Co-Zn DMC are added to a dry high-pressure reactor, heated to 90~110℃, stirred and mixed evenly, and then ethylene oxide is slowly introduced, maintaining a pressure of 3~5 bar. The reaction is carried out until the pressure stabilizes, cooled to room temperature, and the reacting gas is released. The product is neutralized with dilute hydrochloric acid to neutralize the DMC catalyst, and after precipitation, filtration and drying, alcohol polyether (monohydroxy-terminated polyether segment) is obtained. The theoretical molecular weight of alcohol polyether is 4508.1. The molar ratio of benzyl alcohol to EO is 1:120, and the amount of DMC catalyst added is 0.05% of the total mass of benzyl alcohol and EO. (2) To prepare alkoxide by reacting alcohol polyether with sodium hydride: Under a nitrogen atmosphere, monohydroxy-terminated polyether segment and sodium hydride (NaH) are added to a reactor and stirred evenly to ensure that sodium hydride is evenly dispersed to obtain alkoxide. The molar ratio of alcohol polyether to sodium hydride is 1:1. (3) The alkoxide and lactone monomer are ring-opened polymerized under the catalysis of stannous octoate, and acetic acid is added for end capping to obtain a polyether segment and polyester segment block copolymer, wherein the polyester segment ends with hydroxyl groups: ε-caprolactone and stannous octoate toluene solution (0.1% concentration) are added to the reaction system of step (2), heated to 110-140℃, and stirred to ensure uniform mixing. Finally, acetic acid is added to neutralize the terminal sodium salt to generate a hydroxyl-terminated copolymer. After precipitation and purification, a polyether segment and polyester segment block copolymer is obtained, wherein the polyester segment ends with hydroxyl groups. The molar ratio of alcohol polyether, ε-caprolactone and acetic acid is 1:1:1, and the alcohol polyether is calculated based on the theoretical molecular weight (EO mass / molar amount of benzyl alcohol + benzyl alcohol molecular weight). The stannous octoate toluene solution is 0.3% of the total mass of alcohol polyether and ε-caprolactone. (4) React the polyether segment and polyester segment block copolymer with diisocyanate under the catalysis of stannous octoate to obtain isocyanate-terminated polyether segment and polyester segment block copolymer: Under a nitrogen atmosphere, add a certain volume of organic solvent (toluene) to the reactor, control the concentration in the reactor to be 30%~50%, and control the temperature to be 20~40℃. Add the polyether segment and polyester segment block copolymer and isophorone diisocyanate (IPDI) from step (3), and use the remaining stannous octoate as a catalyst, stirring to ensure uniform mixing. Using the isocyanate value (NCO value) as a progress monitoring method, react until the NCO value drops to half of the initial value (representing complete reaction), to obtain isocyanate-terminated polyether segment and polyester segment block copolymer. The molar ratio of polyether segment and polyester segment block copolymer to isophorone diisocyanate is 1:1.(5) React the isocyanate-terminated polyether segments and polyester block copolymers with triazole under the catalysis of stannous octoate, so that the isocyanate groups are blocked by triazole to obtain a polymer: Under a nitrogen atmosphere, add all the products of step (4) to the reactor, then slowly add triazole solution (solvent is toluene) and stir evenly, use the remaining stannous octoate as a catalyst, and heat to 60-80°C; during the reaction, the isocyanate value (NCO value) is used as the progress monitoring method. The reaction ends when the NCO value drops to the set value or below, where the set value is 0.02%. Remove the solvent by vacuum distillation to obtain the polymer. The molar ratio of triazole to isophorone diisocyanate (IPDI) in step (4) is 1.05:1. (6) Mix the polymer with small molecule alkanolamine evenly to obtain a dispersant composition: Dissolve the purified polymer in NMP solvent and mix it evenly with small molecule alkanolamine to obtain a dispersant composition. The total molar ratio of hydroxyl and amino groups in the polymer to that in the small molecule alcoholamine is 1:1.

[0091] The dispersant compositions of Examples 2 to 18 were prepared in the same way as those of Example 1, except that one or more of the following were different: the molar ratio of benzyl alcohol to EO, the molar ratio of triazole to isophorone diisocyanate, the composition of small molecule alkanolamine, and the amount of small molecule alkanolamine. The parameters of the dispersant compositions of Examples 1 to 18 during preparation are shown in Table 1.

[0092] Table 1. Parameters of Examples 1 to 18

[0093]

[0094] Comparative Example 1

[0095] The dispersant in Comparative Example 1 was the polymer from Example 11 above.

[0096] Comparative Example 2

[0097] The dispersant in Comparative Example 2 was isopropanolamine.

[0098] Comparative Example 3

[0099] The dispersant in Comparative Example 3 was a mixture of isopropanolamine and oleyl alcohol polyoxyethylene ether phosphate, wherein the molar ratio of isopropanolamine to oleyl alcohol polyoxyethylene ether phosphate was 1:1.

[0100] Experimental Example 1

[0101] Adhesion stabilization performance: Lithium-ion battery positive electrode slurries were prepared using the dispersant compositions of Examples 1 to 18 and the dispersants of Comparative Examples 1 to 3, respectively, and the adhesion stabilization performance of the lithium-ion battery positive electrode slurries was tested. Specifically, lithium iron phosphate (positive electrode active material), conductive carbon black (conductive agent), polyvinylidene fluoride (binder), and dispersant composition (or dispersant) were added at a mass ratio of 96.9:1:2:0.1, dispersed using a dual planetary disperser, and the solid content was adjusted to 65% with NMP to obtain the lithium-ion battery positive electrode slurry. The above slurry was sealed and stored in a constant temperature and low humidity environment, and the viscosity of the slurry was tested after 24 hours. The lower the slurry viscosity, the stronger the adhesion stabilization performance. The test results are shown in Table 2, where Comparative Example 4 in Table 2 is the blank group, that is, no dispersant was added to the battery positive electrode slurry.

[0102] Flexibility enhancement performance: Positive electrode sheets were prepared using the lithium-ion battery positive electrode slurries of Examples 1 to 18 and Comparative Examples 1 to 3 described above, and the number of cracks on the electrode surface was detected. The flexibility enhancement performance of the dispersant composition was determined based on the number of cracks, with fewer cracks indicating stronger flexibility enhancement performance. The test results are shown in Table 2, where Comparative Example 4 in Table 2 is the blank group, i.e., no dispersant was added to the battery positive electrode slurry.

[0103] Battery cycle performance: The positive electrode sheets of Examples 1 to 18 and Comparative Examples 1 to 3 were used to fabricate pouch batteries, and cycle tests were conducted at a charge-discharge power of 1P. The battery manufacturing process, including rolling parameters, was the same. The battery discharge capacity retention rate after 1000 cycles was compared to assess the battery cycle performance. A higher capacity retention rate indicates less cycle degradation and better cycle performance. The test results are shown in Table 2, where Comparative Example 4 in Table 2 is the blank group, meaning no dispersant was added to the battery positive electrode slurry.

[0104] Table 2. Experimental data of the examples and comparative examples.

[0105]

[0106] The experimental data in Table 2 show that:

[0107] 1. Comparing Examples 1 to 18 with Comparative Examples 1 to 4, the viscosity of the slurry after 24 hours in Examples 1 to 18 was much lower than that in Comparative Example 4. This indicates that the dispersant composition of this application has good adhesion stabilization properties when applied to the positive electrode slurry. In addition, the number of cracks on the electrode surface in Examples 1 to 18 was much lower than that in Comparative Example 4. This indicates that the dispersant composition of this application also has good flexibility enhancement properties. The capacity retention rate after 1000 cycles in Examples 1 to 18 was higher than that in Comparative Example 4. This indicates that the dispersant composition of this application, when applied to the positive electrode slurry, will not deteriorate the battery cycle performance. On the contrary, due to the increased flexibility of the positive electrode, it can improve the battery cycle performance to a certain extent.

[0108] 2. After 24 hours, the viscosity of the slurry in Comparative Example 1 was significantly higher than that in Examples 1 and 4. The number of surface cracks on the positive electrode of Comparative Example 1 was significantly lower than that in Comparative Example 4, and the same as in Examples 1. After 24 hours, the viscosity of the slurry in Comparative Example 2 was significantly lower than that in Comparative Example 4 and lower than that in Examples 2. The number of surface cracks on the positive electrode of Comparative Example 2 was significantly higher than that in Examples 1 and the same as that in Comparative Example 4. Therefore, it can be seen that in the dispersant composition, small molecule alkanolamines play a major role in the slurry's viscosity stabilization. The polyester and polyether segments in the polymer can improve the flexibility of the positive electrode and reduce the viscosity of the electrode. In cases of electrode cracking, neither polymers nor small-molecule alkanolamines alone can simultaneously provide both adhesion stabilization and flexibility, and their improvement on battery cycle performance is very limited. However, the cathode dispersant of this application combines polymers with polyether and polyester segments with small-molecule alkanolamines, achieving both adhesion stabilization and flexibility enhancement. Furthermore, during electrode preparation, the small-molecule alkanolamines react with isocyanate groups to form polyurea and polyurethane structures, further increasing the flexibility and electrolyte resistance of the cathode, thus improving battery performance. In addition, the cycle capacity retention rate of Comparative Example 3 after 1000 cycles is far lower than that of the Example, indicating that ordinary phosphate ester dispersants, even when combined with small-molecule alkanolamines, cannot resolve the impact of the deteriorating cycle performance of the small-molecule alkanolamines.

[0109] Experimental Example 2

[0110] The polymer obtained in step (5) of Example 1 was diluted with NMP to a first test sample with a solid content of 15%. The first test sample was then tested to obtain the following results: Figure 3 The infrared test spectrum is shown.

[0111] The polymer obtained in step (5) of Example 1 was baked at 80°C for half an hour, and then diluted with NMP to a second test sample with a solid content of 15%. The second test sample was then tested to obtain the following results: Figure 4 The infrared test spectrum is shown.

[0112] After baking the dispersant composition obtained in step (6) of Example 1 at 80°C for half an hour, it was diluted with NMP to prepare a third test sample with a solid content of 15%. The third test sample was then tested to obtain the following results: Figure 5 The infrared test spectrum is shown.

[0113] Depend on Figures 3 to 5 It can be known that: Figure 3 At 1100cm -1 1500cm -1 1700cm -1 The left and right peaks correspond to polyether, triazole, and polyester structures, respectively. Therefore, it can be seen that the polymer in this application contains polyether, polyester, and triazole.

[0114] Figure 4 and Figure 3 In comparison, at 2200cm -1 The peaks on the left and right correspond to isocyanate groups, indicating that the polymer in this application is deblocked after heating and regenerates isocyanate groups.

[0115] Figure 5 and Figure 4 In comparison, at 2200cm -1 The disappearance of the peaks on both sides indicates that the isocyanate groups were consumed at this time. This shows that after heating, the isocyanate groups of the polymer in the dispersant composition, which were deblocked after baking, underwent an irreversible reaction with the hydroxyl and amine groups of the small molecule alkanolamine. This further indicates that when the polymer and the small molecule alkanolamine are used as dispersants in the positive electrode slurry, the positive electrode slurry can maintain stable viscosity, and the small molecule alkanolamine can be removed during the preparation of the electrode sheet and not introduced into the lithium battery, thereby ensuring the cycle performance of the lithium battery.

[0116] The technical solutions of this application have been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of this application is obviously not limited to these specific embodiments. Without departing from the principles of this application, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of this application.

Claims

1. The use of a polymer and a small-molecule alkanolamine as dispersants in the preparation of a positive electrode slurry, wherein the polymer is a polymer containing a blocked isocyanate structure, a polyether structure, and a polyester structure, wherein... The blocked isocyanate structure is an isocyanate structure blocked using triazole; The polymer is prepared through the following steps: S1: Provides a block copolymer of polyether segments and polyester segments, wherein the polyester segments are hydroxyl-terminated. S2: React the polyether segment and polyester segment block copolymer with diisocyanate under the catalysis of stannous octoate to obtain isocyanate-terminated polyether segment and polyester segment block copolymer. S3: The isocyanate-terminated polyether segment and polyester block copolymer are reacted with triazole under the catalysis of stannous octoate, so that the triazole blocks the isocyanate group to obtain the polymer. Step S1 specifically includes: S11: The alcohol and epoxide are ring-opening polymerized under the catalysis of DMC catalyst to obtain alcohol polyether, wherein the alcohol is a monohydroxy primary alcohol; S12: React the alcohol polyether with sodium hydride to obtain an alkoxide; S13: The alkoxide and lactone monomer are subjected to ring-opening polymerization under the catalysis of stannous octoate, and acetic acid is added for end-capping to obtain a polyether segment and polyester segment block copolymer, wherein the polyester segment ends with hydroxyl groups.

2. The use according to claim 1, characterized in that, In step S2, the diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; And / or, in step S2, the molar ratio of the polyether-polyester block copolymer to the diisocyanate is 1:1; And / or, the molar ratio of the triazole in step S3 to the diisocyanate in step S2 is (1~1.1):1; And / or, the reaction temperature in step S3 is 60~80℃.

3. The use according to claim 1, characterized in that, In step S2, the diisocyanate is isophorone diisocyanate.

4. The use according to claim 1, characterized in that, In step S11, the alkyl oxide is one or more of ethylene oxide and propylene oxide; And / or, in step S11, the molar ratio of alcohol to alkyl oxide is alcohol:alkyl oxide = 1:(100~150). And / or, in step S11, the DMC catalyst is 0.01% to 0.1% of the total mass of the alcohol and the epoxide; And / or, in step S11, the DMC catalyst comprises Co-Zn DMC; And / or, in step S12, the molar ratio of the alcohol polyether to the sodium hydride is 1:1; And / or, in step S13, the molar ratio of the alkoxide to the lactone monomer is 1:1, and the molar ratio of the alkoxide to the acetic acid is 1:1; And / or, in step S13, the stannous octoate toluene solution is 0.1% to 0.3% of the total mass of the alcohol polyether and the lactone monomer, wherein the concentration of stannous octoate in the stannous octoate toluene solution is 0.1%; And / or, in step S13, the reaction temperature is 110~140℃; And / or, in step S13, the lactone monomer is ε-caprolactone.

5. The use according to claim 4, characterized in that, In step S11, the monohydroxy primary alcohol is benzyl alcohol; And / or, in step S11, the alkylene oxide is ethylene oxide; And / or, in step S11, the DMC catalyst is 0.05% of the total mass of the alcohol and the epoxide.

6. A dispersant composition, characterized in that, The dispersant composition comprises small molecule alcoholamines and polymers. Wherein, the small molecule alcohol amine is an alcohol amine with a molecular weight of no more than 200, and the polymer is a polymer containing a blocked isocyanate structure, a polyether structure and a polyester structure, wherein the blocked isocyanate structure is an isocyanate structure blocked with triazole. The polymer is prepared through the following steps: S1: Provides a block copolymer of polyether segments and polyester segments, wherein the polyester segments are hydroxyl-terminated. S2: React the polyether segment and polyester segment block copolymer with diisocyanate under the catalysis of stannous octoate to obtain isocyanate-terminated polyether segment and polyester segment block copolymer. S3: The isocyanate-terminated polyether segment and polyester block copolymer are reacted with triazole under the catalysis of stannous octoate, so that the triazole blocks the isocyanate group to obtain the polymer. Step S1 specifically includes: S11: The alcohol and epoxide are ring-opening polymerized under the catalysis of DMC catalyst to obtain alcohol polyether, wherein the alcohol is a monohydroxy primary alcohol; S12: React the alcohol polyether with sodium hydride to obtain an alkoxide; S13: The alkoxide and lactone monomer are subjected to ring-opening polymerization under the catalysis of stannous octoate, and acetic acid is added for end-capping to obtain a polyether segment and polyester segment block copolymer, wherein the polyester segment ends with hydroxyl groups.

7. The dispersant composition according to claim 6, characterized in that, In the dispersant composition, the ratio of the total molar amount of hydroxyl and amino groups in the small molecule alkanolamine to the molar amount of the blocked isocyanate structure in the polymer is (amino group + hydroxyl group): polymer = (1~1.2): (1~1.2). And / or, the small molecule alcoholamine includes one or more of isopropanolamine, isobutanolamine, and n-butanolamine.

8. The dispersant composition according to claim 7, characterized in that, In the dispersant composition, the ratio of the total molar amount of hydroxyl and amino groups in the small molecule alkanolamine to the molar amount of the blocked isocyanate structure in the polymer is (amino group + hydroxyl group): polymer = (1~1.2):1; And / or, the small molecule alcoholamines include isopropanolamine.

9. A method for preparing a dispersant composition, used to prepare the dispersant composition according to any one of claims 6 to 8, characterized in that, The preparation method includes: mixing the polymer with the small molecule alcohol amine uniformly to obtain a dispersant composition.

10. The method for preparing the dispersant composition according to claim 9, characterized in that, In step S2, the diisocyanate includes one or more of toluene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; And / or, in step S2, the molar ratio of the polyether-polyester block copolymer to the diisocyanate is 1:1; And / or, the molar ratio of the triazole in step S3 to the diisocyanate in step S2 is (1~1.1):1; And / or, the reaction temperature in step S3 is 60~80℃.

11. The method for preparing the dispersant composition according to claim 10, characterized in that, In step S2, the diisocyanate is isophorone diisocyanate.

12. The method for preparing the dispersant composition according to claim 9, characterized in that, In step S11, the alkyl oxide is one or more of ethylene oxide and propylene oxide; And / or, in step S11, the molar ratio of alcohol to alkyl oxide is alcohol:alkyl oxide = 1:(100~150). And / or, in step S11, the DMC catalyst is 0.01% to 0.1% of the total mass of the alcohol and the epoxide; And / or, in step S11, the DMC catalyst comprises Co-Zn DMC; And / or, in step S12, the molar ratio of the alcohol polyether to the sodium hydride is 1:1; And / or, in step S13, the molar ratio of the alkoxide to the lactone monomer is 1:1, and the molar ratio of the alkoxide to the acetic acid is 1:1; And / or, in step S13, the stannous octoate toluene solution is 0.1% to 0.3% of the total mass of the alcohol polyether and the lactone monomer, wherein the concentration of stannous octoate in the stannous octoate toluene solution is 0.1%; And / or, in step S13, the reaction temperature is 110~140℃; And / or, in step S13, the lactone monomer is ε-caprolactone.

13. Use of the dispersant composition according to any one of claims 6 to 8 as a positive electrode dispersant in the preparation of a positive electrode slurry.

14. A positive electrode slurry, characterized in that, The positive electrode slurry includes a positive electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant is a dispersant composition according to any one of claims 6 to 8.

15. A positive electrode plate, characterized in that, The positive electrode sheet includes a positive current collector and a positive active material layer located on the surface of the positive current collector, wherein the positive active material layer is prepared by coating the positive electrode slurry according to claim 14 onto the surface of the positive current collector.

16. A lithium-ion battery, characterized in that, The lithium-ion battery includes the positive electrode sheet as described in claim 15.

Images