High-dispersity nano aluminum oxide slurry for diaphragm coating and preparation method of high-dispersity nano aluminum oxide slurry

Abstract

The invention provides high-dispersity nanometer aluminum oxide slurry for diaphragm coating and a preparation method thereof, and belongs to the technical field of aluminum oxide slurry. The anchoring agent is introduced, so that aluminum oxide is stably dispersed in a water phase, and sites are provided for subsequent formation of boric acid ester bonds; when the anchoring agent is used, phosphate groups preferentially form strong interface interaction with the surface of aluminum oxide to construct a stable adsorption layer, and catechol groups are distributed on the outer side of the adsorption layer to reduce site competition; a boron-containing flexible ion conducting agent is introduced, the boron-containing flexible ion conducting agent and an anchoring agent catechol site are reversibly complexed to form a boric acid ester bond, the thixotropy and sedimentation resistance of the slurry are regulated and controlled, and the ionization degree of a phenylboronic acid group is improved by regulating the pH so as to improve the solubility in water and the preparation stability; during pulping, a soft aggregate is sheared and scattered, an adsorption layer is formed, then a boron-containing flexible ion conducting agent is dropwise added, a loose three-dimensional dynamic network is constructed, and standing sedimentation retarding, coating shearing viscosity reduction and leveling facilitating and thixotropic recovery after shearing reduction are achieved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of alumina slurry, and relates to a high-dispersity nano-alumina slurry for diaphragm coating and a preparation method thereof. BACKGROUND

[0002] Lithium ion batteries are widely used in consumer electronics, electric vehicles and energy storage systems due to their high energy density and long cycle life. With the continuous improvement of battery energy density, safety problems have become increasingly prominent. In order to improve the heat resistance and safety of the battery, coating a layer of inorganic ceramic coating on the surface of the polyolefin diaphragm has become an industry standard configuration. The ceramic coating not only significantly improves the heat shrinkage resistance of the diaphragm, but also improves the electrolyte wettability to some extent. Ceramic diaphragm coating slurry is mainly divided into solvent type and water-based system, and at present, water-based ceramic slurry has become the mainstream development direction. Traditional water-based ceramic slurry is usually physically mixed by inorganic particles, water-based binder and dispersant. However, the existing water-based slurry technology still has some deficiencies in practical application.

[0003] Traditional alumina coating technology usually adopts a physical mixing method to mix alumina nanoparticles with ordinary binders to prepare a slurry. First, the surface energy of alumina nanoparticles is high, and it is easy to agglomerate in the slurry, resulting in uneven coating, holes or defects, affecting the denseness and protection effect of the coating; second, the bonding force between the coating and the diaphragm substrate mainly depends on the physical adhesion of the binder, and the bonding force is weak, the coating is easy to fall off during battery manufacturing and cycling, affecting the long-term stability and reliability of the battery.

[0004] Secondly, this simple inorganic coating improves safety while not having ion conduction capability itself, often blocking some pores of the diaphragm, increasing the transmission path and resistance of lithium ions, leading to an increase in the internal resistance of the battery, and a decrease in the rate performance and power density. This limits the performance of the battery in application scenarios requiring fast charging and discharging. SUMMARY

[0005] To solve the above problems, the present application aims to provide a high dispersibility nano-alumina slurry for diaphragm coating and a preparation method thereof. The present application prepares an anchoring agent containing phosphoric acid groups and catechol groups to stably disperse alumina in an aqueous phase and provide sites for subsequent formation of borate ester bonds; when used, the phosphoric acid groups of the anchoring agent preferentially form a strong interface with the surface of alumina to construct a stable adsorption layer, and the catechol groups are distributed outside the adsorption layer to reduce site competition; a boron-containing flexible ionophore is introduced, which reversibly complexes with the catechol sites of the anchoring agent to form borate ester bonds, thereby regulating the thixotropy and anti-settling of the slurry; the ionization degree of the phenylboronic acid groups is increased by adjusting the pH to improve the solubility in water and the preparation stability; during slurry preparation, high-speed shearing is used to break up soft agglomerates and form an adsorption layer, and then the boron-containing flexible ionophore is added dropwise to construct a loose three-dimensional dynamic network, thereby achieving slow settling during standing, shear-induced viscosity reduction for easy leveling, thixotropy recovery after shear reduction, and reduction of defects and improvement of uniformity through stirring and vacuum defoaming.

[0006] To achieve this goal, the present application adopts the following technical solutions: In a first aspect, the present application provides a preparation method of a high dispersibility nano-alumina slurry for diaphragm coating, which comprises: S1: preparing a methyl acrylate glycol phosphate solution, adding a sodium hydroxide solution under ice bath stirring to adjust the pH to obtain a pre-neutralized monomer solution, mixing with 3-methacryl dopamine and acrylamide to obtain a mixed monomer solution, adding disodium ethylenediaminetetraacetate under a nitrogen atmosphere to obtain a pre-reaction liquid A, adjusting the pH with a hydrochloric acid solution and then adding a VA-044 initiator to obtain a reaction liquid A, avoiding light reaction, and obtaining an anchoring agent solution after dialysis; S2: removing the polymerization inhibitor from poly(ethylene glycol) methacrylate by loading the chromatographic column with basic alumina to obtain de-inhibited poly(ethylene glycol) methacrylate, adding de-inhibited poly(ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid to a mixed solvent to obtain solution B, wherein the mixed solvent is obtained by compounding ethanol, deionized water and N,N-dimethylformamide; adding azobisisobutyronitrile after warming under a nitrogen atmosphere to obtain reaction liquid C, reacting, and obtaining the initial product after repeated precipitation purification with cold diethyl ether and vacuum drying, adding deionized water and adjusting the pH with sodium hydroxide to obtain a boron-containing flexible ionophore solution; S3: adding alumina powder to the anchoring agent solution, adding deionized water and shearing to obtain a pre-dispersion liquid, adjusting the pH with ammonia water and stirring to add the boron-containing flexible ionophore solution, continuing to stir after the dropwise addition is completed to obtain a pretreated slurry, and vacuum defoaming to obtain a high dispersibility nano-alumina slurry for diaphragm coating.

[0007] As a preferred technical solution of the present application, in step S1, the concentration of the ethylene glycol methacrylate phosphate solution is 30-50%, for example, it can be 30%, 32%, 34%, 36%, 38%, 40%, 42%, 44%, 46%, 48% or 50%, but not limited to the listed values, other values not listed in this range are also applicable.

[0008] In some optional embodiments, the concentration of the sodium hydroxide solution is 2-3M, for example, it can be 2.0M, 2.1M, 2.2M, 2.3M, 2.4M, 2.5M, 2.6M, 2.7M, 2.8M, 2.9M or 3.0M, but not limited to the listed values, other values not listed in this range are also applicable.

[0009] In some optional embodiments, the pH of the ethylene glycol methacrylate phosphate solution is adjusted to 4.5-5.5 using a sodium hydroxide solution, for example, it can be adjusted to 4.5, 4.6, 4.7, 4.8, 4.9, 5.0, 5.1, 5.2, 5.3, 5.4 or 5.5, but not limited to the listed values, other values not listed in this range are also applicable.

[0010] In some optional embodiments, the molar ratio of ethylene glycol methacrylate phosphate to 3-methacryloyl dopamine is (1-2):(1-3), for example, it can be (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0):(1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3.0), but not limited to the listed values, other values not listed in this range are also applicable.

[0011] In some optional embodiments, the molar ratio of ethylene glycol methacrylate phosphate to acrylamide is (1-2):(10-15), for example, it can be (1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9 or 2.0):(10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5 or 15.0), but not limited to the listed values, other values not listed in this range are also applicable.

[0012] In some optional embodiments, the total solid content of the mixed monomer solution is 10-15%, for example, it can be 10.0%, 10.5%, 11.0%, 11.5%, 12.0%, 12.5%, 13.0%, 13.5%, 14.0%, 14.5% or 15.0%, but not limited to the listed values, other values not listed in the range are also applicable.

[0013] In some optional embodiments, the amount of the disodium ethylenediaminetetraacetate is 0.01-0.05% of the total mass of the ethylene glycol methacrylate phosphate, 3-methacryloyl dopamine and acrylamide, for example, it can be 0.010%, 0.014%, 0.018%, 0.022%, 0.026%, 0.030%, 0.034%, 0.038%, 0.042%, 0.046% or 0.050%, but not limited to the listed values, other values not listed in the range are also applicable.

[0014] In some optional embodiments, the concentration of the hydrochloric acid solution is 1-2M, for example, it can be 1.0M, 1.1M, 1.2M, 1.3M, 1.4M, 1.5M, 1.6M, 1.7M, 1.8M, 1.9M or 2.0M, but not limited to the listed values, other values not listed in the range are also applicable.

[0015] In some optional embodiments, the pH of the pre-reaction solution A is adjusted to 4-5 using a hydrochloric acid solution, for example, it can be adjusted to 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.8, 4.9 or 5.0, but not limited to the listed values, other values not listed in the range are also applicable.

[0016] In some optional embodiments, the amount of the VA-044 initiator (azo-diisobutylimidazoline hydrochloride) is 0.5-1% of the total mass of the ethylene glycol methacrylate phosphate, 3-methacryloyl dopamine and acrylamide, for example, it can be 0.50%, 0.55%, 0.60%, 0.65%, 0.70%, 0.75%, 0.80%, 0.85%, 0.90%, 0.95% or 1.00%, but not limited to the listed values, other values not listed in the range are also applicable.

[0017] In some optional embodiments, the temperature of the light-protected reaction of the reaction solution A is 50-60℃, for example, it can be 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃ or 60℃, but not limited to the listed values, other values not listed in the range are also applicable.

[0018] In some optional embodiments, the reaction solution A is reacted in the dark for 8-12 hours, for example, it can be 8.0 hours, 8.4 hours, 8.8 hours, 9.2 hours, 9.6 hours, 10.0 hours, 10.4 hours, 10.8 hours, 11.2 hours, 11.6 hours or 12.0 hours, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0019] In some optional embodiments, the solid content of the anchoring agent solution is 8-12%, for example, it can be 8.0%, 8.4%, 8.8%, 9.2%, 9.6%, 10.0%, 10.4%, 10.8%, 11.2%, 11.6% or 12.0%, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0020] As a preferred technical solution of the present application, in step S2, the volume ratio of ethanol to deionized water in the mixed solvent is (8-9):(2-1), for example, it can be (8.0, 8.1, 8.2, 8.3, 8.4, 8.5, 8.6, 8.7, 8.8, 8.9 or 9.0):(2.0, 1.9, 1.8, 1.7, 1.6, 1.5, 1.4, 1.3, 1.2, 1.1 or 1.0), but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0021] In some optional embodiments, the volume fraction of N,N-dimethylformamide in the mixed solvent is 2-6%, for example, it can be 2.0%, 2.4%, 2.8%, 3.2%, 3.6%, 4.0%, 4.4%, 4.8%, 5.2%, 5.6% or 6.0%, but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0022] In some optional embodiments, the molar ratio of deprotection (ethylene glycol) methacrylate and 3-acrylamidobenzenesulfonic acid is (10-15):(1-3), for example, it can be (10.0, 10.5, 11.0, 11.5, 12.0, 12.5, 13.0, 13.5, 14.0, 14.5 or 15.0):(1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8 or 3.0), but not only limited to the listed values, other values not listed in the range of values are also applicable.

[0023] In some alternative embodiments, the solid content of solution B is 15-20%, for example, it can be 15.0%, 15.5%, 16.0%, 16.5%, 17.0%, 17.5%, 18.0%, 18.5%, 19.0%, 19.5% or 20.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0024] In some alternative embodiments, the solution B is heated to 65-70°C under a nitrogen atmosphere, for example to 65.0°C, 65.5°C, 66.0°C, 66.5°C, 67.0°C, 67.5°C, 68.0°C, 68.5°C, 69.0°C, 69.5°C, or 70.0°C, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0025] In some optional embodiments, the amount of azobisisobutyronitrile fed is 0.5-1.5% of the total mass of de-inhibited poly(ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid, for example, it can be 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4% or 1.5%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0026] In some optional embodiments, the reaction time of the reaction solution C is 12-16 hours, for example, 12.0 hours, 12.4 hours, 12.8 hours, 13.2 hours, 13.6 hours, 14.0 hours, 14.4 hours, 14.8 hours, 15.2 hours, 15.6 hours, or 16.0 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0027] In some optional embodiments, the product is purified by repeated precipitation with cold ether 2-3 times, for example, 2.0 or 3.0 times, but not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0028] In some alternative embodiments, the primary product is added to deionized water and the pH is adjusted to 8-8.5 with sodium hydroxide. For example, the pH can be adjusted to 8.00, 8.05, 8.10, 8.15, 8.20, 8.25, 8.30, 8.35, 8.40, 8.45, or 8.50, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0029] In some optional embodiments, the solid content of the boron-containing flexible ion-conducting agent solution is 5-10%, for example, it can be 5.0%, 5.5%, 6.0%, 6.5%, 7.0%, 7.5%, 8.0%, 8.5%, 9.0%, 9.5% or 10.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0030] As a preferred technical solution of the present invention, in step S3, the particle size of the alumina powder is 300-500nm, for example, it can be 300nm, 320nm, 340nm, 360nm, 380nm, 400nm, 420nm, 440nm, 460nm, 480nm or 500nm, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0031] In some optional embodiments, the mass fraction of alumina powder in the pre-dispersion liquid is 68-78 wt.%, for example, it can be 68 wt.%, 69 wt.%, 70 wt.%, 71 wt.%, 72 wt.%, 73 wt.%, 74 wt.%, 75 wt.%, 76 wt.%, 77 wt.%, or 78 wt.%, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0032] In some optional embodiments, the shear linear velocity of the alumina powder after being added to the anchoring agent solution is 8-12 m / s, for example, it can be 8.0 m / s, 8.4 m / s, 8.8 m / s, 9.2 m / s, 9.6 m / s, 10.0 m / s, 10.4 m / s, 10.8 m / s, 11.2 m / s, 11.6 m / s or 12.0 m / s, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0033] In some optional embodiments, the shearing time of the alumina powder after adding the anchoring agent solution is 30-60 min, for example, it can be 30 min, 33 min, 36 min, 39 min, 42 min, 45 min, 48 min, 51 min, 54 min, 57 min or 60 min, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0034] In some optional embodiments, the mass ratio of the anchoring agent to the alumina powder is (0.5-2.5):100, for example, it can be 0.5:100, 0.7:100, 0.9:100, 1.1:100, 1.3:100, 1.5:100, 1.7:100, 1.9:100, 2.1:100, 2.3:100 or 2.5:100, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0035] In some alternative embodiments, the concentration of the ammonia water is 2-5%, for example, it can be 2.0%, 2.3%, 2.6%, 2.9%, 3.2%, 3.5%, 3.8%, 4.1%, 4.4%, 4.7% or 5.0%, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0036] In some alternative embodiments, the pH of the pre-dispersion solution is adjusted to 7.2-8.2 using ammonia, for example, to 7.2, 7.3, 7.4, 7.5, 7.6, 7.7, 7.8, 7.9, 8.0, 8.1 or 8.2, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0037] In some optional embodiments, the linear velocity of stirring after adjusting the pH of the pre-dispersion with ammonia is 2-5 m / s, for example, it can be 2.0 m / s, 2.3 m / s, 2.6 m / s, 2.9 m / s, 3.2 m / s, 3.5 m / s, 3.8 m / s, 4.1 m / s, 4.4 m / s, 4.7 m / s or 5.0 m / s, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0038] In some optional embodiments, the mass ratio of the boron-containing flexible ion-conducting agent to the alumina powder is (1-3):100, for example, it can be 1.0:100, 1.2:100, 1.4:100, 1.6:100, 1.8:100, 2.0:100, 2.2:100, 2.4:100, 2.6:100, 2.8:100 or 3.0:100, but is not limited to the listed values, other unlisted values ​​within this range are also applicable.

[0039] In some optional embodiments, the boron-containing flexible ion-conducting agent solution is added over a time of 10-30 minutes, for example, 10 minutes, 12 minutes, 14 minutes, 16 minutes, 18 minutes, 20 minutes, 22 minutes, 24 minutes, 26 minutes, 28 minutes, or 30 minutes, but is not limited to the listed values; other unlisted values ​​within this range are also applicable.

[0040] In some optional embodiments, the continued stirring time is 20-30 minutes, for example, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes or 30 minutes, but is not limited to the listed values, and other unlisted values ​​within this range are also applicable.

[0041] Secondly, the present invention provides a highly dispersible nano-alumina slurry for diaphragm coating.

[0042] This application describes the preparation of an anchoring agent that can stably disperse alumina in an aqueous phase and provide sites for subsequent formation of boron ester bonds with boron-containing components. Ethylene glycol methacrylate is pre-neutralized with sodium hydroxide solution in an ice bath, which partially ionizes the phosphate groups, reducing polymerization instability caused by excessively acidic monomers and avoiding the oxidation side reaction of catechol under localized strong alkaline conditions. Subsequently, it is combined with 3-methacryloyldopamine (providing catechol sites) and acrylamide (providing a hydrophilic framework and chain segment flexibility) to form a mixed monomer system. Nitrogen purging reduces the inhibition of free radical polymerization by dissolved oxygen and its effect on the oxidation of catechol. The addition of disodium EDTA complexes trace metal ions, further inhibiting the metal ion-catalyzed oxidation of catechol. The pH of the system is adjusted, and free radical polymerization is initiated using the water-soluble azo initiator VA-044 under light-protected conditions to obtain a copolymer containing phosphate and catechol groups. Dialysis removes unreacted monomers, oligomers, and inorganic salts, resulting in an anchoring agent solution with a more stable composition and more controllable ionic strength. In subsequent use, the phosphate groups of this anchoring agent preferentially form strong interfacial interactions with the hydroxyl / metal sites on the alumina surface, constructing a relatively stable adsorption layer on the particle surface; while the catechol groups do not undertake the main anchoring task, but are more distributed on the outer side of the adsorption layer, providing spatial conditions for dynamic bonding with boron-containing components, thereby reducing site competition between the same functional group and crosslinking.

[0043] This application introduces a boron-containing flexible ion-conducting agent, enabling it to form reversible borate ester bonds with the catechol sites of the anchoring agent in the aqueous phase. This reversible bonding is used to regulate the thixotropy and anti-settling properties of the pulp. Poly(ethylene glycol) methacrylate monomers are first subjected to an alkaline alumina column to remove the polymerization inhibitor, preventing the inhibitor from consuming free radicals and causing a decrease in polymerization conversion or abnormal molecular weight distribution. The de-inhibited (ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid are dissolved in an ethanol / water mixture, with N,N-dimethylformamide added as a co-solvent to improve the solubility of the aromatic boric acid monomer in the system and maintain homogeneity as much as possible, reducing copolymer composition drift. After nitrogen purging, azobisisobutyronitrile is added for free radical copolymerization to obtain a copolymer containing polyethylene glycol segments and phenylboronic acid side groups. The product is repeatedly precipitated with cold diethyl ether and vacuum dried to remove residual monomers, oligomers, and solvents, reducing the impact of impurities and residual solvents during subsequent pulping. The polymer was dissolved in deionized water and the pH was adjusted with sodium hydroxide. This improved the ionization of the phenylboronic acid groups (forming borates), thereby improving the solubility and formulation stability of the boron-containing polymer in water. It also provided a more suitable reaction environment for subsequent complexation with catechol, making the boronic acid / borate sites more likely to participate in dynamic borate ester bonding during the pulping stage.

[0044] This application utilizes anchoring adsorption and a dynamic borate ester network to achieve high dispersion and anti-settling properties of alumina particles, and obtains rheological properties suitable for membrane coating. Alumina is added to the anchoring agent solution and subjected to high-speed shear dispersion. Pre-dispersion is mainly achieved through two synergistic effects: first, shearing provides sufficient mechanical energy to break up soft aggregates; second, the phosphate groups in the anchoring agent molecules form a strong interfacial interaction with the hydroxyl / metal sites on the alumina surface, resulting in a relatively stable adsorption layer on the particle surface. The hydrophilic framework and extended catechol sites of this adsorption layer enhance the hydration stability of the particles and reduce the tendency for re-agglomeration. The pH of the pre-dispersion solution was then adjusted with dilute ammonia, and a boron-containing flexible ion-conducting agent solution was added dropwise under relatively mild shear conditions. The phenylboronic acid / borate sites of the boron-containing polymer reversibly complexed with the catechol sites extended by the anchoring agent to form borate ester bonds, thereby forming a loose three-dimensional dynamic network between particles. When stationary, this network provides certain structural support to the particles, helping to slow down sedimentation. During the coating shearing process, some dynamic bonds can break, reducing the viscosity of the system and facilitating leveling. After shear reduction, the bonds can be recombined to a certain extent, giving the slurry a certain thixotropic recovery ability, which is beneficial to the stability of coating formation. Subsequent stirring is to avoid microgelation / flocculation caused by excessively high local concentrations. Vacuum degassing removes air bubbles introduced by dispersion and stirring, reducing coating defects and improving coating uniformity. This application establishes a dispersion basis through strong anchoring on the particle surface, and then regulates the rheology and stability of the slurry through dynamic borate ester bonds under weakly alkaline conditions to obtain a highly dispersed alumina inorganic slurry suitable for diaphragm coating.

[0045] Compared with the prior art, the beneficial effects of the present invention are as follows: This application prepares an anchoring agent that can stably disperse alumina in an aqueous phase and provide sites for subsequent formation of boron ester bonds with boron-containing components. Through pre-neutralization, deoxygenation, complexation to inhibit oxidation and initiate free radical polymerization, a copolymer with phosphate and catechol groups in the side chain is obtained. When the anchoring agent is used, the phosphate groups preferentially form a strong interfacial interaction with the alumina surface to build a stable adsorption layer, while the catechol groups are distributed on the outside of the adsorption layer to provide space for dynamic bonding, thereby reducing site competition.

[0046] This application introduces a boron-containing flexible ion-conducting agent, enabling it to form reversible borate ester bonds with the catechol sites of the anchoring agent in the aqueous phase. This reversible bonding is used to regulate the thixotropic properties and anti-settling properties of the slurry. By removing the polymerization inhibitor and free radical copolymerization, a copolymer containing polyethylene glycol segments and phenylboronic acid side groups is obtained. Residual monomers, oligomers, and solvents are removed by repeated precipitation and vacuum drying. The copolymer is dissolved in deionized water, and the pH is adjusted to increase the ionization degree of the phenylboronic acid groups, improve water solubility and formulation stability, and provide a more suitable reaction environment for subsequent complexation bonding with catechol, making it easier for the boric acid / borate sites to participate in dynamic borate ester bonding.

[0047] This application utilizes anchoring adsorption and a dynamic borate ester network to achieve high dispersion and anti-settling of alumina particles, and obtains rheological properties suitable for membrane coating. High-speed shearing breaks up soft agglomerates and forms a relatively stable adsorption layer on the particle surface with the anchoring agent, improving hydration stability and reducing the tendency for re-agglomeration. After adjusting the pH of the pre-dispersed solution, a boron-containing flexible ion-conducting agent is added dropwise, allowing it to reversibly complex with the extended catechol sites to form borate ester bonds, creating a loose three-dimensional dynamic network between particles. This slows down sedimentation during standing, reduces viscosity during coating shearing for better leveling, and achieves a certain degree of thixotropic recovery after shear reduction. Subsequent stirring avoids excessively high local concentrations that could lead to microgelation / flocculation, and vacuum degassing removes air bubbles to reduce coating defects and improve coating uniformity. Attached Figure Description

[0048] Figure 1 Infrared spectrum of the anchoring agent prepared by the preparation method described in Example 1 of this application; Figure 2 Infrared spectrum of the boron-containing flexible ion-conducting agent prepared by the preparation method described in Example 1 of this application; Figure 3 Image of the nano-alumina slurry prepared by the preparation method described in Example 1 of this application. Detailed Implementation

[0049] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods or the scope of protection of the present invention. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include any obvious substitutions and modifications made to the embodiments described herein.

[0050] The chemical reagents used in the embodiments and comparative examples of this invention are all commercially available products and have not undergone further purification or processing.

[0051] Example 1 This embodiment provides a highly dispersible nano-alumina slurry for diaphragm coating and its preparation method. The preparation method of the highly dispersible nano-alumina slurry for diaphragm coating specifically includes the following steps: S1: Prepare a 45% ethylene glycol methacrylate solution. Adjust the pH to 5.2 by adding 2.8M sodium hydroxide solution under ice bath stirring to obtain a pre-neutralized monomer solution. Add 3-methacrylamide and acrylamide to obtain a mixed monomer solution, wherein the molar ratio of ethylene glycol methacrylate to 3-methacrylamide is 1.8:2.5, and the molar ratio of ethylene glycol methacrylate to acrylamide is 1.8:14. The total solid content of the mixed monomer solution is 14%. Add ethylenediamine tetrahydroquinone under a nitrogen atmosphere. Disodium acetate was used to obtain pre-reaction solution A, in which the amount of disodium ethylenediaminetetraacetate was 0.04% of the total mass of ethylene glycol methacrylate, 3-methacrylamide and acrylamide. The pH was adjusted to 4.8 with 1.8M hydrochloric acid solution, and then VA-044 initiator was added to obtain reaction solution A. The amount of VA-044 initiator was 0.8% of the total mass of ethylene glycol methacrylate, 3-methacrylamide and acrylamide. The reaction was carried out at 58℃ in the dark for 11 hours. After dialysis, an anchoring agent solution with a solid content of 11% was obtained. Figure 1 The infrared spectrum of the anchoring agent is shown in the figure, 3600-3200 cm⁻¹. -1 The broad peak at approximately 2930 cm⁻¹ can be attributed to the OH / NH stretching vibration, corresponding to the interaction between the catechol hydroxyl and amide groups in the anchoring agent, accompanied by hydration hydrogen bonding, indicating that the system has obvious hydrophilic characteristics; at approximately 2930 cm⁻¹... -1 The absorption is aliphatic CH stretching vibration, indicating that the acrylate / acrylamide copolymer backbone has been formed; at approximately 1660 cm⁻¹ -1 With approximately 1540cm -1The absorption can be attributed to the amide I band (C=O stretching) and the amide II band (NH bending and CN stretching coupling), respectively, proving that the hydrophilic amide segment is introduced and retained; at 1600-1500 cm⁻¹ -1 The absorption in the region can be attributed to aromatic ring skeletal vibrations, indicating the presence of a catechol aromatic structure; at approximately 1250 cm⁻¹ -1 and 1100-900cm -1 The absorption peaks are attributed to the stretching vibrations of P=O and PO (including POC) related to phosphate groups, indicating that the side chains containing phosphate groups have been introduced into the copolymer, providing a structural basis for the subsequent formation of strong interfacial interactions with alumina surface sites.

[0052] S2: Poly(ethylene glycol) methacrylate is passed through a chromatography column packed with alkaline alumina to remove the polymerization inhibitor, resulting in de-inhibited poly(ethylene glycol) methacrylate. The de-inhibited poly(ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid are then added to a mixed solvent to obtain solution B. The mixed solvent is a mixture of ethanol, deionized water, and N,N-dimethylformamide; wherein the volume ratio of ethanol to deionized water in the mixed solvent is 8.5:1.5, and the volume fraction of N,N-dimethylformamide in the mixed solvent is 5%. The molar ratio of ester and 3-acrylamidophenylboronic acid was 14:2.5. The solid content of solution B was 19%. After heating to 69°C under a nitrogen atmosphere, azobisisobutyronitrile was added to obtain reaction solution C. The amount of azobisisobutyronitrile added was 1.2% of the total mass of de-inhibited (ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid. The reaction was carried out for 15 hours. The product was purified by repeated precipitation with cold diethyl ether three times and vacuum dried to obtain the initial product. The product was added to deionized water and the pH was adjusted to 8.4 with sodium hydroxide to obtain a boron-containing flexible ion-conducting agent solution with a solid content of 9%. Figure 2 This is the infrared spectrum of a boron-containing flexible ion-conducting agent. 3600-3200 cm⁻¹ -1 The broad peaks can be attributed to the OH / NH stretching vibration, originating from hydrogen bonding interactions of amide groups, boron-containing sites, and polyether segments; the peaks are located at 2950-2870 cm⁻¹. -1 The absorption can be attributed to aliphatic CH stretching vibrations, indicating that the hydrocarbon backbone of the copolymer main chain and polyether side chains has been formed; at 1730-1710 cm⁻¹ -1 The absorption peaks are attributed to the stretching vibrations of the ester carbonyl group (C=O), indicating that the polyethylene glycol methacrylate segment was introduced into the copolymer; the absorption peaks in the 1660-1540 cm⁻¹ range... -1 The absorption appearing in the range can be attributed to the amide I band / amide II band, indicating that the acrylamide-phenylboronic acid monomer was introduced and retained in the form of an amide structure; the absorption in the 1600-1500 cm⁻¹ range... -1 The absorption peaks can be attributed to aromatic ring skeletal vibrations, consistent with the aromatic ring structure of phenylboronic acid side groups; the peaks are located at 1150-1050 cm⁻¹.-1 The absorption peaks can be attributed to the COC stretching vibrations of the polyether segments; in the 1400-1300 cm⁻¹ range... -1 The absorption in the vicinity can be attributed to the BO vibration of the boron-containing group.

[0053] S3: Alumina powder with a particle size of 450 nm was added to the anchoring agent solution. After adding deionized water, the mixture was sheared at a linear velocity of 11 m / s for 50 min to obtain a pre-dispersion liquid. The mass ratio of the anchoring agent to the alumina powder was 2.0:100, and the mass fraction of the alumina powder in the pre-dispersion liquid was 72 wt.%. The pH was adjusted to 8.0 using 4% ammonia water, and then a boron-containing flexible ion-conducting agent solution was added while stirring at a linear velocity of 4 m / s. The mass ratio of the boron-containing flexible ion-conducting agent to the alumina powder was 2.5:100, and the addition time was 25 min. After the addition was completed, stirring was continued for 28 min to obtain a pretreated slurry. Vacuum degassing was performed to obtain a highly dispersible nano-alumina slurry for diaphragm coating. Figure 3 The image shows the prepared highly dispersible nano-alumina slurry for membrane coating. It is a milky white, homogeneous slurry with no obvious particle texture, no visible coarse agglomerates or flocculent precipitates, and no obvious foam layer.

[0054] Example 2 This embodiment provides a highly dispersible nano-alumina slurry for diaphragm coating and its preparation method. The preparation method of the highly dispersible nano-alumina slurry for diaphragm coating specifically includes the following steps: S1: Prepare a 30% ethylene glycol methacrylate solution. Adjust the pH to 4.5 by adding 2M sodium hydroxide solution under ice bath stirring to obtain a pre-neutralized monomer solution. Add 3-methacrylamide and acrylamide to obtain a mixed monomer solution, wherein the molar ratio of ethylene glycol methacrylate to 3-methacrylamide is 1:1, and the molar ratio of ethylene glycol methacrylate to acrylamide is 1:10. The total solid content of the mixed monomer solution is 10%. Add ethylenediaminetetraethyl... Disodium ethylenediaminetetraacetate was used to obtain pre-reaction solution A, in which the amount of disodium ethylenediaminetetraacetate added was 0.01% of the total mass of ethylene glycol methacrylate, 3-methacryloyldopamine and acrylamide. After adjusting the pH to 4 with 1M hydrochloric acid solution, VA-044 initiator was added to obtain reaction solution A. The amount of VA-044 initiator added was 0.5% of the total mass of ethylene glycol methacrylate, 3-methacryloyldopamine and acrylamide. The reaction was carried out at 50°C in the dark for 8 hours. After dialysis, an anchoring agent solution with a solid content of 8% was obtained. S2: Poly(ethylene glycol) methacrylate is passed through a chromatography column packed with alkaline alumina to remove the polymerization inhibitor, resulting in de-inhibited poly(ethylene glycol) methacrylate. The de-inhibited poly(ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid are then added to a mixed solvent to obtain solution B. The mixed solvent is a mixture of ethanol, deionized water, and N,N-dimethylformamide; wherein the volume ratio of ethanol to deionized water in the mixed solvent is 9:1, and the volume fraction of N,N-dimethylformamide in the mixed solvent is 2%. The molar ratio of ester and 3-acrylamidophenylboronic acid is 10:1. The solid content of solution B is 15%. After heating to 65°C under a nitrogen atmosphere, azobisisobutyronitrile is added to obtain reaction solution C. The amount of azobisisobutyronitrile added is 0.5% of the total mass of de-inhibited (ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid. The reaction is carried out for 12 hours. The product is purified by repeated precipitation twice with cold diethyl ether and vacuum dried to obtain the initial product. The product is added to deionized water and the pH is adjusted to 8 with sodium hydroxide to obtain a boron-containing flexible ion-conducting agent solution with a solid content of 5%. S3: Alumina powder with a particle size of 300 nm was added to the anchoring agent solution. After adding deionized water, the mixture was sheared at a linear velocity of 8 m / s for 30 min to obtain a pre-dispersion liquid. The mass ratio of the anchoring agent to the alumina powder was 0.5:100, and the mass fraction of the alumina powder in the pre-dispersion liquid was 75 wt.%. The pH was adjusted to 7.2 using 2% ammonia water, and then a boron-containing flexible ion-conducting agent solution was added while stirring at a linear velocity of 2 m / s. The mass ratio of the boron-containing flexible ion-conducting agent to the alumina powder was 1:100, and the addition time was 10 min. After the addition was completed, stirring was continued for 20 min to obtain a pretreated slurry. Vacuum degassing was performed to obtain a highly dispersible nano-alumina slurry for membrane coating.

[0055] Example 3 This embodiment provides a highly dispersible nano-alumina slurry for diaphragm coating and its preparation method. The preparation method of the highly dispersible nano-alumina slurry for diaphragm coating specifically includes the following steps: S1: Prepare a 40% ethylene glycol methacrylate solution. Adjust the pH to 4.8 by adding 2.2M sodium hydroxide solution under ice bath stirring to obtain a pre-neutralized monomer solution. Add 3-methacrylamide and acrylamide to obtain a mixed monomer solution, wherein the molar ratio of ethylene glycol methacrylate to 3-methacrylamide is 1.2:1.5, and the molar ratio of ethylene glycol methacrylate to acrylamide is 1.2:11. The total solid content of the mixed monomer solution is 11%. Add ethylenediamine under a nitrogen atmosphere. Disodium tetraacetate was used to obtain pre-reaction solution A, in which the amount of disodium ethylenediaminetetraacetate was 0.02% of the total mass of ethylene glycol methacrylate, 3-methacrylamide and acrylamide. The pH was adjusted to 4.2 with 1.2M hydrochloric acid solution, and then VA-044 initiator was added to obtain reaction solution A. The amount of VA-044 initiator was 0.6% of the total mass of ethylene glycol methacrylate, 3-methacrylamide and acrylamide. The reaction was carried out at 52℃ in the dark for 9 hours. After dialysis, an anchoring agent solution with a solid content of 9% was obtained. S2: Poly(ethylene glycol) methacrylate is passed through a chromatography column packed with alkaline alumina to remove the polymerization inhibitor, resulting in de-inhibited (ethylene glycol) methacrylate. The de-inhibited (ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid are then added to a mixed solvent to obtain solution B. The mixed solvent is a mixture of ethanol, deionized water, and N,N-dimethylformamide; wherein the volume ratio of ethanol to deionized water in the mixed solvent is 8:2, and the volume fraction of N,N-dimethylformamide in the mixed solvent is 3%. The de-inhibited (ethylene glycol) methacrylate... The molar ratio of azobisisobutyronitrile to 3-acrylamidophenylboronic acid was 11:1.5. The solid content of solution B was 16%. After heating to 66°C under a nitrogen atmosphere, azobisisobutyronitrile was added to obtain reaction solution C. The amount of azobisisobutyronitrile added was 0.8% of the total mass of de-inhibited (ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid. The reaction was carried out for 13 hours. The product was purified by repeated precipitation twice with cold diethyl ether and vacuum dried to obtain the initial product. The product was added to deionized water and the pH was adjusted to 8.1 with sodium hydroxide to obtain a boron-containing flexible ion-conducting agent solution with a solid content of 6%. S3: Alumina powder with a particle size of 350 nm was added to the anchoring agent solution. After adding deionized water, the mixture was sheared at a linear velocity of 9 m / s for 40 min to obtain a pre-dispersion liquid. The mass ratio of the anchoring agent to the alumina powder was 1.0:100, and the mass fraction of the alumina powder in the pre-dispersion liquid was 68 wt.%. The pH was adjusted to 7.5 with 3% ammonia water, and then a boron-containing flexible ion-conducting agent solution was added while stirring at a linear velocity of 3 m / s. The mass ratio of the boron-containing flexible ion-conducting agent to the alumina powder was 1.5:100, and the addition time was 15 min. After the addition was completed, stirring was continued for 22 min to obtain a pretreated slurry. Vacuum degassing was performed to obtain a highly dispersible nano-alumina slurry for membrane coating.

[0056] Example 4 This embodiment provides a highly dispersible nano-alumina slurry for diaphragm coating and its preparation method. The preparation method of the highly dispersible nano-alumina slurry for diaphragm coating specifically includes the following steps: S1: Prepare a 50% ethylene glycol methacrylate solution. Adjust the pH to 5.5 by adding 3M sodium hydroxide solution under ice bath stirring to obtain a pre-neutralized monomer solution. Add 3-methacrylamide and acrylamide to obtain a mixed monomer solution, wherein the molar ratio of ethylene glycol methacrylate to 3-methacrylamide is 2:3, and the molar ratio of ethylene glycol methacrylate to acrylamide is 2:15. The total solid content of the mixed monomer solution is 15%. Add ethylenediaminetetraethyl... Disodium ethylenediaminetetraacetate was used to obtain pre-reaction solution A, in which the amount of disodium ethylenediaminetetraacetate added was 0.05% of the total mass of ethylene glycol methacrylate, 3-methacryloyldopamine and acrylamide. After adjusting the pH to 5 with 2M hydrochloric acid solution, VA-044 initiator was added to obtain reaction solution A. The amount of VA-044 initiator added was 1% of the total mass of ethylene glycol methacrylate, 3-methacryloyldopamine and acrylamide. The reaction was carried out at 60℃ in the dark for 12 hours. After dialysis, an anchoring agent solution with a solid content of 12% was obtained. S2: Poly(ethylene glycol) methacrylate is passed through a chromatography column packed with alkaline alumina to remove the polymerization inhibitor, resulting in de-inhibited poly(ethylene glycol) methacrylate. The de-inhibited poly(ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid are then added to a mixed solvent to obtain solution B. The mixed solvent is a mixture of ethanol, deionized water, and N,N-dimethylformamide; wherein the volume ratio of ethanol to deionized water in the mixed solvent is 8.8:1.2, and the volume fraction of N,N-dimethylformamide in the mixed solvent is 6%. The molar ratio of ester and 3-acrylamidophenylboronic acid is 15:3. The solid content of solution B is 20%. After heating to 70°C under a nitrogen atmosphere, azobisisobutyronitrile is added to obtain reaction solution C. The amount of azobisisobutyronitrile added is 1.5% of the total mass of de-inhibited (ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid. The reaction is carried out for 16 hours. The product is purified by repeated precipitation with cold diethyl ether three times and vacuum dried to obtain the initial product. The product is added to deionized water and the pH is adjusted to 8.5 with sodium hydroxide to obtain a boron-containing flexible ion-conducting agent solution with a solid content of 10%. S3: Alumina powder with a particle size of 500 nm was added to the anchoring agent solution. After adding deionized water, the mixture was sheared at a linear velocity of 12 m / s for 60 min to obtain a pre-dispersion liquid. The mass ratio of the anchoring agent to the alumina powder was 2.5:100, and the mass fraction of the alumina powder in the pre-dispersion liquid was 78 wt.%. The pH was adjusted to 8.2 using 5% ammonia water, and then a boron-containing flexible ion-conducting agent solution was added while stirring at a linear velocity of 5 m / s. The mass ratio of the boron-containing flexible ion-conducting agent to the alumina powder was 3:100, and the addition time was 30 min. After the addition was completed, stirring was continued for 30 min to obtain a pretreated slurry. Vacuum degassing was performed to obtain a highly dispersible nano-alumina slurry for membrane coating.

[0057] Comparative Example 1 This comparative example provides a highly dispersible nano-alumina slurry for diaphragm coating. The difference from Example 1 is that ethylene glycol phosphate methacrylate is not added in S1, while the other operating steps and process parameters are exactly the same as in Example 1.

[0058] Comparative Example 2 This comparative example provides a highly dispersible nano-alumina slurry for diaphragm coating. The difference from Example 1 is that 3-methylacrylamide dopamine is not added in S1, while the other operating steps and process parameters are exactly the same as in Example 1.

[0059] Comparative Example 3 This comparative example provides a highly dispersible nano-alumina slurry for diaphragm coating. The difference from Example 1 is that no boron-containing flexible ion-conducting agent solution is added in S3, while the other operating steps and process parameters are exactly the same as in Example 1.

[0060] Comparative Example 4 This comparative example provides a highly dispersible nano-alumina slurry for diaphragm coating. The difference from Example 1 is that no anchoring agent solution is added in S3, while the other operating steps and process parameters are exactly the same as in Example 1.

[0061] Ceramic diaphragms were prepared from the highly dispersed nano-alumina slurries used for diaphragm coating in Examples 1-4 and Comparative Examples 1-4, and their performance was tested. The specific process is as follows: Peel strength was tested according to GB / T 2792-2014; Air permeability: The air permeability of the diaphragm was tested using a Gurley 4110 air permeability tester; Tensile strength (transverse) was tested according to GB / T1040.3-2006. The heat shrinkage rate (transverse) of the sample was tested according to ASTM D1204. The puncture strength of the sample was tested according to ASTM D3763; The test results are shown in Table 1.

[0062] Table 1. Performance test results of highly dispersed nano-alumina slurries for diaphragm coating in Examples 1-4 and Comparative Examples 1-4. ; From the test results of Example 1 and Comparative Example 1 in Table 1, it can be seen that in S1, without the addition of ethylene glycol methacrylate, the anchoring agent lacks the interfacial interaction of phosphate groups on the hydroxyl / metal sites of the alumina surface. The stable adsorption layer on the particle surface is difficult to establish sufficiently, making it more prone to re-agglomeration and local flocculation after slurry preparation, resulting in decreased microscopic uniformity of the coating during film formation. Due to insufficient effective anchoring at the particle-base film interface, the coating is more prone to interfacial cracking and particle detachment under drying shrinkage and peel loads, thus reducing peel strength. Agglomerates and local accumulation make the channels more easily blocked or form uneven resistance channels, making the gas passage path more tortuous and increasing air permeability resistance, thus reducing air permeability. Uneven coating and interfacial defects weaken the stress transmission and overall load-bearing capacity of the diaphragm, making stress concentration and premature failure more likely at defects during stretching, thus reducing tensile strength. Due to the discontinuous distribution of the ceramic support phase and weakened high-temperature constraint on the polyolefin base film, dimensional stability decreases after heating, thus increasing thermal shrinkage. Because agglomeration defects and insufficient interfacial bonding reduce local resistance to damage, local peeling and rapid crack propagation are more likely to occur under puncture load, thus reducing puncture strength.

[0063] As shown in Table 1, the test results of Example 1 and Comparative Example 2 reveal that S1 lacks 3-methacrylamide dopamine, and the anchoring agent lacks catechol sites. This results in insufficient sites for forming reversible borate ester bonds with the boron-containing flexible ion-conducting agent, making it difficult to construct an effective dynamic network and network-locking structure during film formation. Consequently, the contributions of thixotropic recovery of the slurry and enhanced coating cohesion are weakened. Due to insufficient dynamic bonding and network locking, the interparticle connections and coating cohesion decrease after drying and film formation. The interface is more prone to interlayer slip and microcrack propagation under peel load, thus reducing peel strength. The lack of dynamic network constraint on particle distribution makes micro-migration and local densification differences more likely during coating, leading to a more non-uniform pore structure and increased local resistance, thus reducing permeability. The weakened coating cohesion and interfacial synergy make the coating more susceptible to becoming a defect source during stretching, inducing premature local failure of the base film, thus reducing tensile strength. The lack of synergistic constraint of the network structure on the particle / polymer phase at high temperatures weakens the ceramic layer's ability to inhibit thermal shrinkage of the base film, thus increasing the thermal shrinkage rate. Insufficient interparticle bonding and cohesion make it easier for cracks to propagate along the particle interface under puncture load, thus reducing puncture strength.

[0064] As shown in Table 1, the test results of Example 1 and Comparative Example 3 reveal that without the addition of a boron-containing flexible ion-conducting agent solution in S3, the system lacks the process of forming reversible borate bonds between phenylboronic acid / borate sites and catechol sites. This prevents the establishment of a loose three-dimensional dynamic network between particles to regulate thixotropy and anti-settling properties. Consequently, the slurry lacks structural support during settling, and its structural recovery ability decreases after coating, leading to poor coating uniformity and film stability. Due to the lack of a dynamic network contributing to interparticle connectivity and film-forming locking during drying, the coating's cohesive strength and interfacial stability decrease, making it easier for particles to detach or interlayer damage occur during peeling, thus reducing peel strength. The particle distribution is more prone to localized accumulation or particle-depleted areas, resulting in poor pore resistance and channel continuity, leading to increased overall air permeability and decreased air permeability. Coating defects and insufficient cohesion reduce stress transfer efficiency, making stress concentration and premature fracture more likely in weak areas of the coating during stretching, thus reducing tensile strength. The uneven ceramic layer structure and reduced constraint weaken the inhibition of shrinkage of the base film at high temperatures, resulting in increased thermal shrinkage. Due to the lack of dynamic interparticle connections, cracks are more likely to penetrate through the particle interface under puncture load, thus reducing puncture strength.

[0065] From the test results of Example 1 and Comparative Example 4 in Table 1, it can be seen that without the addition of anchoring agent solution in S3, the alumina particles lack a stable adsorption layer and hydration stability support, making dispersion more dependent on mechanical shearing. After shearing stops, they are more prone to agglomeration, flocculation, and sedimentation. During coating and film formation, they are more likely to form large particle defects and local pore blockage, and the particle-base film interface lacks effective anchoring and fixation. Due to insufficient interfacial adhesion and increased powder shedding tendency, interface failure and coating peeling are more likely to occur under peel load, thus reducing peel strength. Because agglomerates and local pore blockage severely obstruct gas channels and make the passage path more tortuous, the gas permeability resistance increases significantly, thus reducing permeability. Due to large coating defects and weak interfacial bonding, stress concentration is more severe, and local premature failure is more likely to occur during stretching, thus reducing tensile strength. Due to poor continuity of the ceramic support phase and insufficient high-temperature constraint on the base film, the dimensional stability at high temperature decreases significantly, thus increasing the thermal shrinkage rate. Because agglomeration defects and interfacial debonding make local cracking and rapid crack propagation more likely to occur under puncture load, the puncture strength decreases.

[0066] The above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for preparing a highly dispersible nano-alumina slurry for diaphragm coating, characterized in that, The preparation method includes: S1: Prepare a ethylene glycol phosphate methacrylate solution. Add sodium hydroxide solution to adjust the pH under ice bath stirring to obtain a pre-neutralized monomer solution. Add 3-methacrylamide and acrylamide to obtain a mixed monomer solution. Add disodium ethylenediaminetetraacetate under nitrogen atmosphere to obtain pre-reaction solution A. Adjust the pH with hydrochloric acid solution and add VA-044 initiator to obtain reaction solution A. React in the dark and dialyze to obtain anchoring agent solution. S2: Poly(ethylene glycol) methacrylate is passed through a chromatography column packed with alkaline alumina to remove the polymerization inhibitor, resulting in de-inhibited poly(ethylene glycol) methacrylate. The de-inhibited poly(ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid are added to a mixed solvent to obtain solution B, wherein the mixed solvent is a mixture of ethanol, deionized water, and N,N-dimethylformamide. After heating under a nitrogen atmosphere, azobisisobutyronitrile is added to obtain reaction solution C. The reaction is carried out, and the product is purified by repeated precipitation with cold diethyl ether and vacuum dried to obtain the initial product. The initial product is added to deionized water and the pH is adjusted with sodium hydroxide to obtain a boron-containing flexible ion-conducting agent solution. S3: Add alumina powder to the anchoring agent solution, add deionized water and shear to obtain a pre-dispersed liquid. Adjust the pH with ammonia water and stir to add boron-containing flexible ion-conducting agent solution. After the addition is completed, continue stirring to obtain a pretreated slurry. Vacuum degassing is used to obtain a highly dispersible nano alumina slurry for membrane coating.

2. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S1: The molar ratio of ethylene glycol methacrylate to 3-methacryloyldopamine is (1-2):(1-3); The molar ratio of ethylene glycol methacrylate to acrylamide is (1-2):(10-15); The total solids content of the mixed monomer solution is 10-15%.

3. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S1: The amount of disodium ethylenediaminetetraacetate added is 0.01-0.05% of the total mass of ethylene glycol methacrylate, 3-methacrylamide, and acrylamide. The amount of VA-044 initiator added is 0.5-1% of the total mass of ethylene glycol methacrylate, 3-methacrylamide, and acrylamide. The solid content of the anchoring agent solution is 8-12%.

4. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S2: The volume ratio of ethanol to deionized water in the mixed solvent is (8-9):(2-1); The volume fraction of N,N-dimethylformamide in the mixed solvent is 2-6%.

5. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S2: The molar ratio of the de-inhibited poly(ethylene glycol) methacrylate to 3-acrylamidophenylboronic acid is (10-15):(1-3); The solid content of solution B is 15-20%.

6. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S2: The amount of azobisisobutyronitrile added is 0.5-1.5% of the total mass of de-inhibited (ethylene glycol) methacrylate and 3-acrylamidophenylboronic acid; The solid content of the boron-containing flexible ion-conducting agent solution is 5-10%.

7. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S3: The alumina powder has a particle size of 300-500 nm.

8. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S3: The mass ratio of the anchoring agent to the alumina powder is (0.5-2.5):

100.

9. The method for preparing a highly dispersible nano-alumina slurry for diaphragm coating according to claim 1, characterized in that, In S3: The mass ratio of the boron-containing flexible ion-conducting agent to the alumina powder is (1-3):

100.

10. A highly dispersible nano-alumina slurry for diaphragm coating prepared by the preparation method according to any one of claims 1-9.

Images