Modified binder, water-based edge coating, preparation method and edge coating

Abstract

The invention relates to a modified binder, a water-based edge coating, a preparation method and an edge coating layer. The modified binder comprises cyano-functionalized polyacrylic acid and nano aluminum oxide dispersed in the cyano-functionalized polyacrylic acid. The cyano group is introduced into the polyacrylic acid, so that the chemical bonding effect between the polyacrylic acid and the positive electrode active material can be enhanced, and the positive electrode stripping force is improved; and meanwhile, nano aluminum oxide is introduced on the basis, so that the insulating property is remarkably improved. According to the water-based edge coating containing the modified binder, an edge coating layer prepared through coating has excellent binding performance and relatively high insulativity, electrolyte permeation and lithium dendrite growth can be effectively inhibited, meanwhile, the stability of an electrode structure can be enhanced, and a new thought is provided for optimization of a current collector of a high-energy-density lithium ion battery.

Description

Technical Field

[0001] This invention belongs to the field of battery technology and relates to a modified binder, a water-based edge coating, a preparation method, and an edge coating layer. Background Technology

[0002] Lithium-ion batteries (LiB) have been widely used in consumer electronics, transportation, power tools, and energy storage. Among these, aluminum foil current collectors refer to composite materials formed by combining aluminum foil with other materials (such as paper, plastic film, and coatings). These composite materials can endow aluminum foil with new properties and functions to meet the application needs of different industries.

[0003] In the lithium battery industry, carbon-coated current collector technology is commonly used to improve lithium battery performance. To further ensure the safety of the current collector, a ceramic layer is typically coated at the edge of the carbon-coated current collector (i.e., edge coating). This edge coating process, by applying ceramic slurry to the edge of the carbon-coated current collector, achieves multiple technical benefits: first, it reduces the risk of short circuits and thermal runaway in lithium batteries, meeting the high safety standards for power batteries; second, it reduces edge side reactions such as lithium plating and corrosion, extending battery cycle life; and third, it allows for more flexible optimization of electrode thickness or material systems through edge protection. Therefore, the edge coating process at the edge of the carbon-coated current collector effectively eliminates edge risks, improves the reliability and overall performance of lithium-ion batteries, and is a key step in the detailed optimization process of lithium battery manufacturing.

[0004] In existing technologies, aqueous edge coating slurries have been developed to improve the safety of lithium batteries. However, conventional aqueous edge coating slurries only focus on coating thickness, insulation, and miscibility during design, often neglecting the adhesion performance between the edge coating layer and the current collector. Specifically, the coating of aqueous edge coating slurries is usually completed simultaneously with the preparation of the water-washed edge-coated sample, or the carbon coating and edge coating processes are completed before coating the positive electrode active material. However, during the coating of the positive electrode active material, it is inevitable that active material will be coated onto the edge coating area. Since the design of the carbon coating layer takes into account the adhesion to the electrode end, while the design of the edge coating layer does not consider this adhesion requirement, the active material in the edge coating area is prone to peeling off after the positive electrode material is baked and rolled, affecting the structural stability and performance of the battery.

[0005] Therefore, developing a water-based edge coating with both high adhesion and high insulation, and correspondingly providing a modified binder, a water-based edge coating, a preparation method, and a current collector, is of great practical significance and application value for solving the problem of active material peeling in existing edge coating processes and further improving the reliability and service life of lithium-ion batteries. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a modified binder, an aqueous edge coating, a preparation method, and an edge coating layer. The modified binder provided by the present invention can enhance the chemical bonding between itself and the positive electrode active material, thereby improving the positive electrode peeling force; at the same time, it can significantly improve the insulation performance; the aqueous edge coating containing the modified binder has both excellent adhesion performance and high insulation performance, which can effectively inhibit electrolyte penetration and lithium dendrite growth, while also enhancing the stability of the electrode structure, providing a new approach for optimizing the current collector of high energy density lithium-ion batteries.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a modified adhesive comprising cyano-functionalized polyacrylic acid and nano-alumina dispersed in the cyano-functionalized polyacrylic acid.

[0009] This invention introduces cyano groups into polyacrylic acid, which enhances its chemical bonding with the positive electrode active material and improves the positive electrode peeling force. Simultaneously, the introduction of nano-alumina significantly improves insulation performance. The water-based edge coating containing a modified binder, after application, produces an edge coating that combines excellent adhesion and high insulation, effectively inhibiting electrolyte penetration and lithium dendrite growth, while also enhancing the stability of the electrode structure. This provides a new approach for optimizing current collectors in high-energy-density lithium-ion batteries.

[0010] Specifically, this invention introduces cyano groups into polyacrylic acid (PAA). The cyano group has a single atom with strong electronegativity and a carbon-nitrogen triple bond, making it a highly polar functional group. This polarity can form stronger dipole-dipole or ion-dipole interactions with metal ions or oxygen atoms on the surface of the cathode material, thereby improving interfacial adhesion. In addition, although PAA itself forms hydrogen bonds with hydroxyl groups (-OH) on the surface of the cathode material through carboxyl groups (-COOH), after the introduction of cyano groups, the nitrogen atom of the cyano group may also participate in hydrogen bond formation (such as with -OH or residual moisture on the material surface), providing additional adhesion sites. Nano-alumina is a wide bandgap insulating material with a bandgap of approximately 8 eV to 9 eV. Its nanoparticles dispersed in the PAA matrix can directly block electron conduction paths, reducing the conductivity of the composite material. In addition, a large number of heterogeneous interfaces are formed between nano-alumina and PAA. The energy level differences at these interfaces can lead to charge accumulation (interface polarization), hindering the directional movement of electrons or ions, thus improving insulation. Uniformly dispersed nano-alumina forms a maze effect in PAA, extending the electron or ion conduction path (similar to the "zigzag path" model), significantly increasing the bulk resistance.

[0011] In some embodiments, the mass ratio of the cyanofunctionalized polyacrylic acid to the nano-alumina is 10:1 to 100:1.

[0012] Secondly, the present invention provides a method for preparing a modified adhesive, the method comprising the following steps:

[0013] A cyano group is introduced into polyacrylic acid by esterification to obtain cyano-functionalized polyacrylic acid; nano-alumina is dispersed in the cyano-functionalized polyacrylic acid by blending to obtain the modified binder described in the first aspect.

[0014] In some embodiments, the esterification reaction includes: mixing polyacrylic acid, a cyaniding agent, a catalyst, and an organic solvent, carrying out the esterification reaction under a protective atmosphere, and then post-processing the resulting product to obtain the cyanofunctionalized polyacrylic acid.

[0015] In some embodiments, the cyaniding agent includes any one or a combination of at least two of cyanoacetamide, cyanoacetonitrile, or cyanoethanol.

[0016] In some embodiments, the catalyst comprises any one or a combination of at least two of p-toluenesulfonic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, or sulfuric acid.

[0017] In some embodiments, the organic solvent includes any one or a combination of at least two of toluene, dimethylformamide, or dimethyl sulfoxide.

[0018] In some embodiments, the mass ratio of the polyacrylic acid, cyaniding agent and organic solvent is 1:(2~3):(8~12).

[0019] In some embodiments, the amount of catalyst used is 5% to 10% of the molar amount of polyacrylic acid.

[0020] In some embodiments, the esterification reaction is carried out at a temperature of 110°C to 120°C.

[0021] In some embodiments, the esterification reaction takes 6 to 12 hours.

[0022] In some embodiments, the blending method includes: surface modification of nano-alumina to obtain surface-modified alumina; dispersion of cyanofunctionalized polyacrylic acid in water to obtain PAA slurry; uniform dispersion of surface-modified alumina in the PAA slurry; and after drying and annealing, dispersion of nano-alumina in the cyanofunctionalized polyacrylic acid to obtain the modified binder.

[0023] In some embodiments, the surface modification includes surface modification of nano-alumina using ethylenediaminetetraacetic acid.

[0024] In some embodiments, the particle size Dv50 of the nano-alumina is 15nm~25nm, and Dv90 is 90nm~110nm.

[0025] In some embodiments, the cyanofunctionalized polyacrylic acid content in the PAA slurry is 5wt% to 10wt%.

[0026] In some embodiments, the drying temperature is above 80°C and the time is above 24 hours.

[0027] In some embodiments, the annealing temperature is 100°C to 150°C.

[0028] Thirdly, the present invention provides a water-based edge coating, the water-based edge coating comprising boehmite, deionized water, wetting agent, pH adjuster, dispersant, and the modified binder described in the first aspect.

[0029] The mass ratio of boehmite to the modified binder is 100:(20~30);

[0030] The mass ratio of boehmite to the dispersant is 100:(2~4).

[0031] Fourthly, the present invention provides a method for preparing a water-based edge coating, the method comprising the following steps:

[0032] (1) Mix deionized water with the modified adhesive described in the first aspect to obtain an adhesive solution;

[0033] (2) Mix the dispersant with the adhesive solution, and then add a portion of boehmite and the remainder of boehmite in sequence to obtain an insulating slurry; the portion of boehmite accounts for 40% to 60% of the total boehmite;

[0034] (3) Then mix water with the insulating slurry and adjust the solid content to 8wt%~12wt%; then add pH adjuster to pH value 8~9; then mix with wetting agent and homogenize to obtain the water-based edge coating described in the third aspect.

[0035] In some embodiments, the solid content of the adhesive solution in step (1) is 15wt%~25wt%, and the viscosity is 800mPa·s~3000mPa·s.

[0036] In some embodiments, the wetting agent includes any one or a combination of at least two of polyether siloxanes, modified polyether siloxanes, or alcohol reagents.

[0037] In some embodiments, the pH adjuster includes a sodium hydroxide solution;

[0038] In some embodiments, the dispersant includes ethylenediaminetetraacetic acid (EDTA).

[0039] Fifthly, the present invention provides an edge coating layer, wherein the edge coating layer is obtained by edge coating with the water-based edge coating material described in the third aspect.

[0040] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0041] Compared with the prior art, the present invention has the following beneficial effects:

[0042] This invention introduces cyano groups into polyacrylic acid, which enhances its chemical bonding with the positive electrode active material and improves the positive electrode peeling force. Simultaneously, the introduction of nano-alumina significantly improves insulation performance. The water-based edge coating containing a modified binder, after application, produces an edge coating that combines excellent adhesion and high insulation, effectively inhibiting electrolyte penetration and lithium dendrite growth, while also enhancing the stability of the electrode structure. This provides a new approach for optimizing current collectors in high-energy-density lithium-ion batteries. Detailed Implementation

[0043] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention.

[0044] The "range" disclosed in this invention can be defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. This type of range definition can include or exclude endpoints; any endpoint can be independently included or excluded, and they can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60~120 and 80~110 are listed for specific parameters, it is understood that ranges of 60~110 and 80~120 are also expected. Furthermore, if minimum range values ​​1 and 2 are listed, and maximum range values ​​3, 4, and 5 are also listed, then the following ranges are all expected: 1~3, 1~4, 1~5, 2~3, 2~4, and 2~5. In this invention, unless otherwise stated, the numerical range "a~b" represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range "0~5" indicates that all real numbers between "0" and "5" have been listed in this article; "0~5" is simply a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥2, it is equivalent to listing integers such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. For instance, when a parameter is described as an integer selected from "2~10", it is equivalent to listing the integers 2, 3, 4, 5, 6, 7, 8, 9, and 10.

[0045] In this invention, "a combination of at least two" refers to a quantity greater than or equal to two, unless otherwise specified. For example, "any combination of one or at least two" means one or more or more items. It can be understood that when referring to "a combination of at least two," it refers to any suitable combination of multiple items, that is, a combination of "at least two" items carried out in a manner that does not conflict with and enables the implementation of this invention.

[0046] Unless otherwise specified, all embodiments and optional embodiments of the present invention can be combined with each other to form new technical solutions.

[0047] The term "embodiment" as used in this invention means that a specific feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a mutually exclusive, independent, or alternative embodiment. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described in this invention can be combined with other embodiments.

[0048] Those skilled in the art will understand that the order in which the steps are written in the methods of the various embodiments does not imply a strict execution order. The detailed execution order of each step should be determined by its function and possible internal logic. Unless otherwise specified, all steps of the present invention may be performed sequentially or randomly, but are preferably performed sequentially. For example, if the method includes steps (a) and (b), it means that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), meaning that step (c) can be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0049] In this invention, open-ended technical features or solutions described using terms such as "comprising" do not exclude additional members beyond those listed unless otherwise specified. They can be considered as providing both closed-ended features or solutions comprised of the listed members and open-ended features or solutions that include additional members beyond the listed members. For example, A includes a1, a2, and a3. Unless otherwise specified, it may also include other members or exclude additional members. This can be considered as providing both technical features or solutions where "A is composed of a1, a2, and a3" or "A is selected from a1, a2, and a3," and technical features or solutions where "A includes not only a1, a2, and a3, but also other members."

[0050] In this invention, unless otherwise specified, the features or solutions corresponding to "and / or" include any one of two or more of the related listed items, as well as any and all combinations of the related listed items. These arbitrary and all combinations include any two related listed items, any more related listed items, or a combination of all related listed items. For example, "A and / or B" represents a group consisting of A, B, and "a combination of A and B". "Containing A and / or B" can mean "containing A, containing B, and containing A and B", or "containing A, containing B, or containing A and B", and can be appropriately understood according to the context.

[0051] In this invention, the terms "first aspect," "second aspect," "third aspect," "fourth aspect," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or quantity, nor should they be construed as implicitly indicating the importance or quantity of the indicated technical features. Moreover, "first," "second," "third," "fourth," etc., serve only as a non-exhaustive enumeration and should be understood not to constitute a closed limitation on the quantity.

[0052] In this invention, "optional" means that something is optional, that is, it refers to either "with" or "without". If there are multiple "optional" options in a technical solution, unless otherwise specified, and there are no contradictions or mutual constraints, then each "optional" option is independent.

[0053] In a first aspect, the present invention provides a modified adhesive comprising cyano-functionalized polyacrylic acid and nano-alumina dispersed in the cyano-functionalized polyacrylic acid.

[0054] This invention introduces cyano groups into polyacrylic acid, which enhances its chemical bonding with the positive electrode active material and improves the positive electrode peeling force. Simultaneously, the introduction of nano-alumina significantly improves insulation performance. The water-based edge coating containing a modified binder, after application, produces an edge coating that combines excellent adhesion and high insulation, effectively inhibiting electrolyte penetration and lithium dendrite growth, while also enhancing the stability of the electrode structure. This provides a new approach for optimizing current collectors in high-energy-density lithium-ion batteries.

[0055] Specifically, this invention introduces cyano groups into polyacrylic acid (PAA). The cyano group has a single atom with strong electronegativity and a carbon-nitrogen triple bond, making it a highly polar functional group. This polarity can form stronger dipole-dipole or ion-dipole interactions with metal ions or oxygen atoms on the surface of the cathode material, thereby improving interfacial adhesion. In addition, although PAA itself forms hydrogen bonds with hydroxyl groups (-OH) on the surface of the cathode material through carboxyl groups (-COOH), after the introduction of cyano groups, the nitrogen atom of the cyano group may also participate in hydrogen bond formation (such as with -OH or residual moisture on the material surface), providing additional adhesion sites. Nano-alumina is a wide bandgap insulating material with a bandgap of approximately 8 eV to 9 eV. Its nanoparticles dispersed in the PAA matrix can directly block electron conduction paths, reducing the conductivity of the composite material. In addition, a large number of heterogeneous interfaces are formed between nano-alumina and PAA. The energy level differences at these interfaces can lead to charge accumulation (interface polarization), hindering the directional movement of electrons or ions, thus improving insulation. Uniformly dispersed nano-alumina forms a maze effect in PAA, extending the electron or ion conduction path (similar to the "zigzag path" model), significantly increasing the bulk resistance.

[0056] In some embodiments, the mass ratio of the cyanofunctionalized polyacrylic acid to the nano-alumina is 10:1 to 100:1, for example, it can be 10:1, 20:1, 30:1, 40:1, 50:1, 60:1, 70:1, 80:1, 90:1 or 100:1, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0057] Secondly, the present invention provides a method for preparing a modified adhesive, the method comprising the following steps:

[0058] A cyano group is introduced into polyacrylic acid by esterification to obtain cyano-functionalized polyacrylic acid; nano-alumina is dispersed in the cyano-functionalized polyacrylic acid by blending to obtain the modified binder described in the first aspect.

[0059] In some embodiments, the esterification reaction includes: mixing polyacrylic acid, a cyaniding agent, a catalyst, and an organic solvent, carrying out the esterification reaction under a protective atmosphere, and then post-processing the resulting product to obtain the cyanofunctionalized polyacrylic acid.

[0060] Optionally, the polyacrylic acid is dried to remove moisture before use, which can be done by vacuum drying. For example, vacuum drying at a temperature of 55°C to 65°C for 20 to 28 hours.

[0061] Optionally, the organic solvent can be dehydrated to remove moisture before use, which can be done by adding anhydrous magnesium sulfate to the organic solvent and then filtering.

[0062] In some embodiments, the cyaniding agent includes any one or a combination of at least two of cyanoacetamide, cyanoacetonitrile, or cyanoethanol. Typical but non-limiting combinations include combinations of cyanoacetamide and cyanoacetonitrile, cyanoacetonitrile and cyanoethanol, cyanoacetamide and cyanoethanol, cyanoacetonitrile and cyanoethanol, or combinations of cyanoacetamide, cyanoacetonitrile, and cyanoethanol.

[0063] In some embodiments, the catalyst comprises any one or a combination of at least two of p-toluenesulfonic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, or sulfuric acid. Typical but non-limiting combinations include a combination of p-toluenesulfonic acid and 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, a combination of p-toluenesulfonic acid and sulfuric acid, a combination of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and sulfuric acid, or a combination of p-toluenesulfonic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and sulfuric acid.

[0064] In some embodiments, the organic solvent includes any one or a combination of at least two of toluene, dimethylformamide, or dimethyl sulfoxide. Typical but non-limiting combinations include combinations of toluene and dimethylformamide, combinations of dimethylformamide and dimethyl sulfoxide, combinations of toluene and dimethyl sulfoxide, or combinations of toluene, dimethylformamide, and dimethyl sulfoxide.

[0065] In some embodiments, the mass ratio of the polyacrylic acid, cyaniding agent and organic solvent is 1:(2~3):(8~12).

[0066] The mass ratio of polyacrylic acid to cyanide is 1:2 to 1:3, for example, it can be 1:2, 1:2.1, 1:2.4, 1:2.5, 1:2.7, 1:2.8 or 1:3, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0067] The mass ratio of polyacrylic acid to organic solvent is 1:8 to 1:12, for example, it can be 1:8, 1:9, 1:10, 1:11 or 1:12, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0068] In some embodiments, the amount of catalyst used is 5% to 10% of the molar amount of polyacrylic acid, for example, it can be 5%, 6%, 7%, 8%, 9% or 10%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0069] In some embodiments, the temperature of the esterification reaction is 110°C to 120°C, for example, 110°C, 112°C, 114°C, 115°C, 116°C, 118°C or 120°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0070] In some embodiments, the esterification reaction time is 6h to 12h, for example, 6h, 7h, 8h, 9h, 10h, 11h or 12h, but not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0071] In some embodiments, the blending method includes: surface modification of nano-alumina to obtain surface-modified alumina; dispersion of cyanofunctionalized polyacrylic acid in water to obtain PAA slurry; uniform dispersion of surface-modified alumina in the PAA slurry; and after drying and annealing, dispersion of nano-alumina in the cyanofunctionalized polyacrylic acid to obtain the modified binder.

[0072] This invention effectively prevents the agglomeration of nano-alumina particles and improves their compatibility with cyano-functionalized polyacrylic acid by modifying the surface of nano-alumina.

[0073] In some embodiments, the surface modification includes surface modification of nano-alumina using ethylenediaminetetraacetic acid.

[0074] Optionally, the method for surface modification of nano-alumina using ethylenediaminetetraacetic acid includes: ultrasonically dispersing nano-alumina in ethanol, then adding ethylenediaminetetraacetic acid, and magnetically stirring at 55℃~65℃ for 1.5h~2.5h to achieve full dispersion; and washing with ethanol at least 3 times after centrifugation.

[0075] In some embodiments, the particle size Dv50 of the nano-alumina is 15nm~25nm, and Dv90 is 90nm~110nm.

[0076] The particle size Dv50 of the nano-alumina is 15nm~25nm, for example, it can be 15nm, 18nm, 20nm, 21nm, 24nm or 25nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0077] The particle size Dv90 of nano alumina is 90nm~110nm, for example, it can be 90nm, 95nm, 100nm, 105nm or 110nm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0078] In some embodiments, the content of cyanofunctionalized polyacrylic acid in the PAA slurry is 5wt% to 10wt%, for example, it can be 5wt%, 6wt%, 7wt%, 8wt%, 9wt% or 10wt%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0079] In some embodiments, the drying temperature is above 80°C and the time is above 24 hours.

[0080] In some embodiments, the annealing temperature is 100°C to 150°C, for example, it can be 100°C, 110°C, 120°C, 130°C, 140°C or 150°C, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0081] This invention uses annealing to remove the participating solvent and improve crystallinity.

[0082] Optionally, the method for uniformly dispersing surface-modified alumina in the PAA slurry includes: first ultrasonically dispersing for 1 to 2 hours, and then magnetically stirring for more than 24 hours at 30°C to 40°C.

[0083] Thirdly, the present invention provides a water-based edge coating, the water-based edge coating comprising boehmite, deionized water, wetting agent, pH adjuster, dispersant, and the modified binder described in the first aspect.

[0084] The mass ratio of boehmite to the modified binder is 100:(20~30), for example, it can be 100:20, 100:24, 100:25, 100:28 or 100:30, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0085] The mass ratio of boehmite to the dispersant is 100:(2~4), for example, it can be 100:2, 100:3 or 100:4, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0086] Fourthly, the present invention provides a method for preparing a water-based edge coating, the method comprising the following steps:

[0087] (1) Mix deionized water with the modified adhesive described in the first aspect to obtain an adhesive solution;

[0088] (2) Mix the dispersant with the adhesive solution, and then add a portion of boehmite and the remainder of boehmite in sequence to obtain an insulating slurry; the portion of boehmite accounts for 40% to 60% of the total boehmite, for example, it can be 40%, 45%, 50%, 55% or 60%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0089] (3) Then mix water with the insulating slurry and adjust the solid content to 8wt%~12wt%; then add pH adjuster to pH value 8~9; then mix with wetting agent and homogenize to obtain the water-based edge coating described in the third aspect.

[0090] In some embodiments, the solid content of the adhesive solution in step (1) is 15wt%~25wt%, and the viscosity is 800mPa·s~3000mPa·s.

[0091] The solid content of the slurry is 15wt% to 25wt%, for example, it can be 15wt%, 16wt%, 18wt%, 20wt%, 21wt%, 24wt% or 25wt%, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0092] The viscosity of the slurry is 800 mPa·s to 3000 mPa·s, for example, it can be 800 mPa·s, 1000 mPa·s, 1200 mPa·s, 1500 mPa·s, 1600 mPa·s, 1800 mPa·s, 2000 mPa·s, 2400 mPa·s, 2500 mPa·s, 2800 mPa·s or 3000 mPa·s, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0093] In some embodiments, the wetting agent includes any one or a combination of at least two of polyether siloxanes, modified polyether siloxanes, or alcohol reagents.

[0094] In some embodiments, the pH adjuster includes a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution can be 0.08 mol / L to 0.12 mol / L, for example, 0.08 mol / L, 0.09 mol / L, 0.1 mol / L, 0.11 mol / L or 0.12 mol / L, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0095] In some embodiments, the dispersant includes ethylenediaminetetraacetic acid (EDTA).

[0096] In some embodiments, when mixing the dispersant, the mixture is dispersed at a speed of 200 rpm to 600 rpm for more than 20 minutes to improve dispersibility; the speed may be 200 rpm, 300 rpm, 400 rpm, 500 rpm or 600 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0097] In some embodiments, when a portion of boehmite is added, it is dispersed at a speed of 2000 rpm to 2600 rpm for more than 30 minutes; the speed can be 2000 rpm, 2100 rpm, 2200 rpm, 2400 rpm, 2500 rpm or 2600 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0098] In some embodiments, when adding the remaining boehmite, it is dispersed at a speed of 2000 rpm to 2600 rpm for more than 20 minutes; the speed can be 2000 rpm, 2100 rpm, 2200 rpm, 2400 rpm, 2500 rpm or 2600 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0099] In some embodiments, when mixing water and the insulating slurry in step (3), the mixture is dispersed at a speed of 2000 rpm to 2600 rpm for more than 30 minutes; the speed may be 2000 rpm, 2100 rpm, 2200 rpm, 2400 rpm, 2500 rpm or 2600 rpm, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0100] In some embodiments, when mixing with a wetting agent, the mixture is stirred at a speed of 10 rpm to 15 rpm for 30 min to 45 min; the speed can be 10 rpm, 11 rpm, 12 rpm, 13 rpm, 14 rpm or 15 rpm, etc., and the stirring time can be 30 min, 32 min, 35 min, 38 min, 40 min, 42 min or 45 min, etc.

[0101] In some embodiments, the homogenization includes homogenizing at least twice at a pressure of 600 bar.

[0102] As a preferred technical solution for the preparation method of water-based edge coating, the preparation method includes the following steps:

[0103] S1. Mix polyacrylic acid, cyaniding agent, catalyst, and organic solvent, and carry out an esterification reaction at 110℃~120℃ for 6h~12h under a nitrogen atmosphere. During the esterification reaction, the generated water is removed by a water separator. After the reaction, saturated NaHCO3 solution is added to wash until neutral. The organic phase is separated by a separatory funnel, dried with anhydrous magnesium sulfate, filtered, and the organic solvent is removed by rotary evaporation. The concentrated liquid is slowly added dropwise to cold methanol, and a white solid precipitates. The white solid is washed with anhydrous ethanol more than 3 times to remove unreacted cyaniding agent, and then dried under vacuum to obtain the cyanofunctionalized polyacrylic acid.

[0104] The polyacrylic acid is dried to remove moisture before use, which can be done by vacuum drying. For example, vacuum drying at a temperature of 55℃~65℃ for 20h~28h; the organic solvent is dehydrated to remove moisture before use, which can be done by adding anhydrous magnesium sulfate to the organic solvent and then filtering.

[0105] The cyaniding agent is cyanoacetamide, the catalyst is p-toluenesulfonic acid, and the organic solvent is toluene;

[0106] The mass ratio of the polyacrylic acid, cyaniding agent, and organic solvent is 1:(2~3):(8~12), and the amount of catalyst used is 5%~10% of the molar amount of the polyacrylic acid.

[0107] S2. Surface modification of nano-alumina is performed using ethylenediaminetetraacetic acid (EDTA) to obtain surface-modified alumina; cyanofunctionalized polyacrylic acid is dispersed in water to obtain a PAA slurry with a cyanofunctionalized polyacrylic acid content of 5wt%~10wt%. Then, the surface-modified alumina is uniformly dispersed in the PAA slurry. After drying and annealing at 100℃~150℃, the nano-alumina is dispersed in the cyanofunctionalized polyacrylic acid to obtain a modified binder.

[0108] The method for surface modification of nano-alumina using ethylenediaminetetraacetic acid (EDTA) includes: ultrasonically dispersing nano-alumina with a Dv50 of 15 nm to 25 nm and a Dv90 of 90 nm to 110 nm in ethanol, then adding EDTA, and magnetically stirring at 55 °C to 65 °C for 1.5 h to 2.5 h to achieve full dispersion; washing with ethanol at least 3 times after centrifugation.

[0109] The drying temperature is above 80℃ and the time is above 24 hours;

[0110] The method for uniformly dispersing surface-modified alumina in the PAA slurry includes: first ultrasonically dispersing for 1 to 2 hours, and then magnetically stirring for more than 24 hours at 30°C to 40°C.

[0111] S3. Mix deionized water and modified adhesive to obtain an adhesive solution with a solid content of 15wt%~25wt% and a viscosity of 800mPa·s~3000mPa·s;

[0112] S4. Mix the dispersant with the adhesive solution, and then add a portion of boehmite and the remainder of boehmite in sequence to obtain an insulating slurry; the portion of boehmite accounts for 40% to 60% of the total boehmite, for example, it can be 40%, 45%, 50%, 55% or 60%, but is not limited to the listed values, and other unlisted values ​​within the range are also applicable.

[0113] The dispersant is ethylenediaminetetraacetic acid. When mixing the dispersant, disperse at a speed of 200 rpm to 600 rpm for more than 20 minutes to improve dispersibility. When adding some boehmite, disperse at a speed of 2000 rpm to 2600 rpm for more than 30 minutes. When adding the remaining boehmite, disperse at a speed of 2000 rpm to 2600 rpm for more than 20 minutes.

[0114] S5. Then mix water with the insulating slurry and adjust the solid content to 8wt%~12wt%; then add a pH adjuster to a pH value of 8~9; then mix with a wetting agent and homogenize to obtain the water-based edge coating.

[0115] In the water-based edge coating, the mass ratio of boehmite to the modified binder is 100:(20~30), and the mass ratio of boehmite to the dispersant is 100:(2~4).

[0116] When mixing water with the insulating slurry, disperse at a speed of 2000 rpm to 2600 rpm for at least 30 minutes; when mixing with the wetting agent, stir at a speed of 10 rpm to 15 rpm for 30 minutes to 45 minutes.

[0117] The homogenization includes homogenizing at least twice at a pressure of 600 bar;

[0118] The pH adjuster is a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution can be 0.08 mol / L to 0.12 mol / L.

[0119] Fifthly, the present invention provides an edge coating layer, wherein the edge coating layer is obtained by edge coating with the water-based edge coating material described in the third aspect.

[0120] To clearly illustrate the technical solution of the present invention, the drug information used in the following specific embodiments is as follows. The listed drug information is only for the purpose of clearly illustrating the technical solution of the present invention and is not intended to further limit the technical solution:

[0121] Polyacrylic acid, Sinopharm Group, model is powder, MW~2000 (Wokai) 25g, Sinopharm code XW01900301402;

[0122] Toluene, Sinopharm Group, model number AR (Shanghai Trial), Sinopharm code 10022818;

[0123] Anhydrous magnesium sulfate, Sinopharm Group, model number Acros-413480025, Sinopharm code C413480025;

[0124] Cyanoacetamide, Sinopharm Group, model number 98% (Shanghai Trial), national drug code 39159170;

[0125] p-Toluenesulfonic acid, Sinopharm Group, model number 99% (Wokai), Sinopharm code XW0110415407;

[0126] Sodium bicarbonate, Sinopharm Group, model number AR (Shanghai Trial), national drug code 10018960;

[0127] Nano-alumina, Zhejiang Manli Nanotechnology Co., Ltd., model number is ML-Al2O3-YN100;

[0128] Ethylenediaminetetraacetic acid (EDTA), produced by Sinopharm Group, model number AR (Shanghai Trial), national drug code 10009617;

[0129] Anhydrous ethanol, Sinopharm Group, model number AR (Shanghai Trial), national drug code 10009218.

[0130] Example 1

[0131] This embodiment provides a method for preparing a water-based edge coating, including the following steps:

[0132] S1. Polyacrylic acid, cyaniding agent, catalyst, and organic solvent were mixed and esterified at 115°C for 9 hours under a nitrogen atmosphere. Water generated during the esterification process was removed using a water separator. After the reaction, saturated NaHCO3 solution was added to wash until neutral. The organic phase was separated by a separatory funnel, dried with anhydrous magnesium sulfate, filtered, and the organic solvent was removed by rotary evaporation. The concentrated liquid was slowly added dropwise to cold methanol, and a white solid precipitated. The white solid was washed three times with anhydrous ethanol to remove unreacted cyaniding agent and dried under vacuum at 50°C for 24 hours to obtain cyanofunctionalized polyacrylic acid.

[0133] The polyacrylic acid is dried to remove moisture before use by vacuum drying at 60°C for 24 hours; the organic solvent is dehydrated to remove moisture before use by adding anhydrous magnesium sulfate to the organic solvent and then filtering.

[0134] The cyaniding agent is cyanoacetamide, the catalyst is p-toluenesulfonic acid, and the organic solvent is toluene;

[0135] The mass ratio of the polyacrylic acid, cyaniding agent, and organic solvent is 1:2:8, and the amount of catalyst used is 8% of the molar amount of the polyacrylic acid.

[0136] S2. Surface modification of nano-alumina is performed using ethylenediaminetetraacetic acid to obtain surface-modified alumina; cyanofunctionalized polyacrylic acid is dispersed in water to obtain a PAA slurry with a cyanofunctionalized polyacrylic acid content of 8 wt%. Then, the surface-modified alumina is uniformly dispersed in the PAA slurry. After drying and annealing at 130°C, the nano-alumina is dispersed in the cyanofunctionalized polyacrylic acid to obtain a modified binder.

[0137] In the modified adhesive, the mass ratio of cyanofunctionalized polyacrylic acid to the nano-alumina is 50:1;

[0138] The method of surface modification of nano-alumina using ethylenediaminetetraacetic acid includes: ultrasonically dispersing nano-alumina with a Dv50 of 20 nm and a Dv90 of 100 nm in ethanol, then adding ethylenediaminetetraacetic acid, and magnetically stirring at 60 °C for 2 h to fully disperse; washing three times with ethanol after centrifugation.

[0139] The drying temperature is 80℃, and the time is 24 hours;

[0140] The method for uniformly dispersing surface-modified alumina in the PAA slurry includes: first ultrasonically dispersing for 1.5 h, and then magnetically stirring at 35°C for 24 h;

[0141] S3. Mix deionized water and modified adhesive to obtain an adhesive solution with a solid content of 20wt% and a viscosity of 2000mPa·s.

[0142] S4. Mix the dispersant with the adhesive solution, then add a portion of boehmite and the remainder of boehmite sequentially to obtain an insulating slurry; the portion of boehmite accounts for 50% of the total boehmite.

[0143] The dispersant is ethylenediaminetetraacetic acid. When mixing the dispersant, disperse at 400 rpm for 20 min to improve dispersibility; when adding some boehmite, disperse at 2400 rpm for 30 min; when adding the remaining boehmite, disperse at 2400 rpm for 20 min.

[0144] S5. Then, mix water with the insulating slurry and adjust the solid content to 10 wt%; then add a pH adjuster to a pH value of 8.5; then mix with a wetting agent (isopropanol), and after homogenization, obtain the water-based edge coating; in the water-based edge coating, the mass ratio of boehmite to modified binder is 100:25, and the mass ratio of boehmite to dispersant is 100:3;

[0145] The water-based edge coating contains 70 wt% boehmite, 3 wt% dispersant, and 10 wt% wetting agent.

[0146] When mixing water with the insulating slurry, disperse at 2400 rpm for 30 minutes; when mixing with the wetting agent, stir at 12 rpm for 40 minutes.

[0147] The homogenization includes two homogenizations at a pressure of 600 bar.

[0148] The pH adjuster is a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0149] Example 2

[0150] This embodiment provides a method for preparing a water-based edge coating, including the following steps:

[0151] S1. A mixture of polyacrylic acid, cyaniding agent, catalyst, and organic solvent was subjected to an esterification reaction at 110°C for 12 hours under a nitrogen atmosphere. During the esterification reaction, the generated water was removed using a water separator. After the reaction, saturated NaHCO3 solution was added to wash until neutral. The organic phase was separated using a separatory funnel, dried with anhydrous magnesium sulfate, filtered, and the organic solvent was removed by rotary evaporation. The concentrated solution was slowly added dropwise to cold methanol, precipitating a white solid. The white solid was washed three times with anhydrous ethanol to remove unreacted cyaniding agent and dried under vacuum at 50°C for 24 hours to obtain cyanofunctionalized polyacrylic acid.

[0152] The polyacrylic acid is dried to remove moisture before use by vacuum drying at 55°C for 28 hours; the organic solvent is dehydrated to remove moisture before use by adding anhydrous magnesium sulfate to the organic solvent and then filtering.

[0153] The cyaniding agent is cyanoacetamide, the catalyst is p-toluenesulfonic acid, and the organic solvent is toluene;

[0154] The mass ratio of the polyacrylic acid, cyaniding agent, and organic solvent is 1:3:12, and the amount of catalyst used is 5% of the molar amount of the polyacrylic acid.

[0155] S2. Surface modification of nano-alumina is performed using ethylenediaminetetraacetic acid to obtain surface-modified alumina; cyanofunctionalized polyacrylic acid is dispersed in water to obtain a PAA slurry with a cyanofunctionalized polyacrylic acid content of 5 wt%. Then, the surface-modified alumina is uniformly dispersed in the PAA slurry. After drying and annealing at 100°C, the nano-alumina is dispersed in the cyanofunctionalized polyacrylic acid to obtain a modified binder.

[0156] In the modified adhesive, the mass ratio of cyanofunctionalized polyacrylic acid to the nano-alumina is 50:1;

[0157] The method for surface modification of nano-alumina using ethylenediaminetetraacetic acid (EDTA) includes: ultrasonically dispersing nano-alumina with a Dv50 of 15 nm and a Dv90 of 90 nm in ethanol, then adding EDTA, and magnetically stirring at 55 °C for 2.5 h to ensure full dispersion; then washing three times with ethanol after centrifugation.

[0158] The drying temperature is 80℃, and the time is 24 hours;

[0159] The method for uniformly dispersing surface-modified alumina in the PAA slurry includes: first ultrasonically dispersing for 1 hour, and then magnetically stirring at 30°C for 24 hours;

[0160] S3. Mix deionized water and modified adhesive to obtain an adhesive solution with a solid content of 15wt% and a viscosity of 800mPa·s.

[0161] S4. Mix the dispersant with the adhesive solution, then add a portion of boehmite and the remainder of boehmite sequentially to obtain an insulating slurry; the portion of boehmite accounts for 40% of the total boehmite.

[0162] The dispersant is ethylenediaminetetraacetic acid. When mixing the dispersant, disperse at 200 rpm for 20 min to improve dispersibility. When adding some boehmite, disperse at 2000 rpm for 30 min. When adding the remaining boehmite, disperse at 2000 rpm for 20 min.

[0163] S5. Then mix water with the insulating slurry and adjust the solid content to 8 wt%; then add a pH adjuster to a pH value of 8; then mix with a wetting agent (isopropanol), and after homogenization, obtain the water-based edge coating; in the water-based edge coating, the mass ratio of boehmite to modified binder is 100:20, and the mass ratio of boehmite to dispersant is 100:2.

[0164] When mixing water with the insulating slurry, disperse at 2000 rpm for 30 minutes; when mixing with the wetting agent, stir at 10 rpm for 45 minutes.

[0165] The homogenization includes two homogenizations at a pressure of 600 bar.

[0166] The pH adjuster is a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0167] Example 3

[0168] This embodiment provides a method for preparing a water-based edge coating, including the following steps:

[0169] S1. Polyacrylic acid, cyaniding agent, catalyst, and organic solvent were mixed and esterified at 120°C for 6 hours under a nitrogen atmosphere. Water generated during the esterification process was removed using a water separator. After the reaction, saturated NaHCO3 solution was added to wash until neutral. The organic phase was separated by a separatory funnel, dried with anhydrous magnesium sulfate, filtered, and the organic solvent was removed by rotary evaporation. The concentrated solution was slowly added dropwise to cold methanol, and a white solid precipitated. The white solid was washed three times with anhydrous ethanol to remove unreacted cyaniding agent and dried under vacuum at 50°C for 24 hours to obtain cyanofunctionalized polyacrylic acid.

[0170] The polyacrylic acid is dried to remove moisture before use by vacuum drying at 65°C for 20 hours; the organic solvent is dehydrated to remove moisture before use by adding anhydrous magnesium sulfate to the organic solvent and then filtering.

[0171] The cyaniding agent is cyanoacetamide, the catalyst is p-toluenesulfonic acid, and the organic solvent is toluene;

[0172] The mass ratio of the polyacrylic acid, cyaniding agent, and organic solvent is 1:2:12, and the amount of catalyst used is 10% of the molar amount of the polyacrylic acid.

[0173] S2. Surface modification of nano-alumina is performed using ethylenediaminetetraacetic acid to obtain surface-modified alumina; cyanofunctionalized polyacrylic acid is dispersed in water to obtain a PAA slurry with a cyanofunctionalized polyacrylic acid content of 10 wt%. Then, the surface-modified alumina is uniformly dispersed in the PAA slurry. After drying and annealing at 150°C, the nano-alumina is dispersed in the cyanofunctionalized polyacrylic acid to obtain a modified binder.

[0174] In the modified adhesive, the mass ratio of cyanofunctionalized polyacrylic acid to the nano-alumina is 50:1;

[0175] The method for surface modification of nano-alumina using ethylenediaminetetraacetic acid (EDTA) includes: ultrasonically dispersing nano-alumina with a Dv50 of 25 nm and a Dv90 of 110 nm in ethanol, then adding EDTA, and magnetically stirring at 65 °C for 1.5 h to ensure full dispersion; after centrifugation, washing with ethanol three times.

[0176] The drying temperature is 80℃, and the time is 24 hours;

[0177] The method for uniformly dispersing surface-modified alumina in the PAA slurry includes: first ultrasonically dispersing for 2 hours, and then magnetically stirring at 40°C for 24 hours;

[0178] S3. Mix deionized water and modified adhesive to obtain an adhesive solution with a solid content of 25wt% and a viscosity of 3000mPa·s.

[0179] S4. Mix the dispersant with the adhesive solution, then add a portion of boehmite and the remainder of boehmite sequentially to obtain an insulating slurry; the portion of boehmite accounts for 60% of the total boehmite.

[0180] The dispersant is ethylenediaminetetraacetic acid. When mixing the dispersant, disperse at 600 rpm for 20 min to improve dispersibility; when adding part of boehmite, disperse at 2600 rpm for 30 min; when adding the remaining boehmite, disperse at 2600 rpm for 20 min.

[0181] S5. Then mix water with the insulating slurry and adjust the solid content to 12wt%; then add a pH adjuster to a pH value of 9; then mix with a wetting agent (isopropanol), and after homogenization, obtain the water-based edge coating; in the water-based edge coating, the mass ratio of boehmite to modified binder is 100:30, and the mass ratio of boehmite to dispersant is 100:4.

[0182] When mixing water with the insulating slurry, disperse at 2600 rpm for 30 minutes; when mixing with the wetting agent, stir at 15 rpm for 30 minutes.

[0183] The homogenization includes two homogenizations at a pressure of 600 bar.

[0184] The pH adjuster is a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0185] Example 4

[0186] This embodiment provides a method for preparing a water-based edge coating. Except that the mass ratio of cyanofunctionalized polyacrylic acid to the nano-alumina in the modified binder is 10:1, all other aspects are the same as in Example 1.

[0187] Example 5

[0188] This embodiment provides a method for preparing a water-based edge coating. Except that the mass ratio of cyanofunctionalized polyacrylic acid to the nano-alumina in the modified binder is 100:1, all other aspects are the same as in Example 1.

[0189] Example 6

[0190] This embodiment provides a method for preparing a water-based edge coating. Except for the modified adhesive, in which the mass ratio of cyanofunctionalized polyacrylic acid to the nano-alumina is 5:1, all other aspects are the same as in Example 1.

[0191] Example 7

[0192] This embodiment provides a method for preparing a water-based edge coating. Except for the modified binder, in which the mass ratio of cyanofunctionalized polyacrylic acid to the nano-alumina is 120:1, all other aspects are the same as in Example 1.

[0193] Comparative Example 1

[0194] This comparative example provides a method for preparing a water-based edge coating, comprising the following steps:

[0195] S1. A mixture of polyacrylic acid, cyaniding agent, catalyst, and organic solvent was subjected to an esterification reaction at 115°C for 9 hours under a nitrogen atmosphere. During the esterification reaction, the generated water was removed using a water separator. After the reaction, saturated NaHCO3 solution was added to wash until neutral. The organic phase was separated using a separatory funnel, dried with anhydrous magnesium sulfate, filtered, and the organic solvent was removed by rotary evaporation. The concentrated liquid was slowly added dropwise to cold methanol, precipitating a white solid. The white solid was washed three times with anhydrous ethanol to remove unreacted cyaniding agent and dried under vacuum at 50°C for 24 hours to obtain cyanofunctionalized polyacrylic acid as a modified binder.

[0196] The polyacrylic acid is dried to remove moisture before use by vacuum drying at 60°C for 24 hours; the organic solvent is dehydrated to remove moisture before use by adding anhydrous magnesium sulfate to the organic solvent and then filtering.

[0197] The cyaniding agent is cyanoacetamide, the catalyst is p-toluenesulfonic acid, and the organic solvent is toluene;

[0198] The mass ratio of the polyacrylic acid, cyaniding agent, and organic solvent is 1:2:8, and the amount of catalyst used is 8% of the molar amount of the polyacrylic acid.

[0199] S2. Mix deionized water and modified adhesive to obtain an adhesive solution with a solid content of 20wt%.

[0200] S3. Mix the dispersant with the adhesive solution, then add a portion of boehmite and the remainder of boehmite sequentially to obtain an insulating slurry; the portion of boehmite accounts for 50% of the total boehmite.

[0201] The dispersant is ethylenediaminetetraacetic acid. When mixing the dispersant, disperse at 400 rpm for 20 min to improve dispersibility; when adding some boehmite, disperse at 2400 rpm for 30 min; when adding the remaining boehmite, disperse at 2400 rpm for 20 min.

[0202] S4. Then mix water with the insulating slurry and adjust the solid content to 10 wt%; then add a pH adjuster to a pH value of 8.5; then mix with a wetting agent (isopropanol), and after homogenization, obtain the water-based edge coating; in the water-based edge coating, the mass ratio of boehmite to modified binder is 100:25, and the mass ratio of boehmite to dispersant is 100:3;

[0203] When mixing water with the insulating slurry, disperse at 2400 rpm for 30 minutes; when mixing with the wetting agent, stir at 12 rpm for 40 minutes.

[0204] The homogenization includes two homogenizations at a pressure of 600 bar.

[0205] The pH adjuster is a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0206] Comparative Example 2

[0207] This comparative example provides a method for preparing a water-based edge coating, comprising the following steps:

[0208] S1. Surface modification of nano-alumina is performed using ethylenediaminetetraacetic acid to obtain surface-modified alumina; polyacrylic acid is dispersed in water to obtain a PAA slurry with a polyacrylic acid content of 8wt%, and then the surface-modified alumina is uniformly dispersed in the PAA slurry. After drying and annealing at 130°C, the nano-alumina is dispersed in the polyacrylic acid to obtain a modified binder.

[0209] The method of surface modification of nano-alumina using ethylenediaminetetraacetic acid includes: ultrasonically dispersing nano-alumina with a Dv50 of 20 nm and a Dv90 of 100 nm in ethanol, then adding ethylenediaminetetraacetic acid, and magnetically stirring at 60 °C for 2 h to fully disperse; washing three times with ethanol after centrifugation.

[0210] The drying temperature is 80℃, and the time is 24 hours;

[0211] The method for uniformly dispersing surface-modified alumina in the PAA slurry includes: first ultrasonically dispersing for 1.5 h, and then magnetically stirring at 35°C for 24 h;

[0212] S2. Mix deionized water and modified adhesive to obtain an adhesive solution with a solid content of 20wt% and a viscosity of 2000mPa·s.

[0213] S3. Mix the dispersant with the adhesive solution, then add a portion of boehmite and the remainder of boehmite sequentially to obtain an insulating slurry; the portion of boehmite accounts for 50% of the total boehmite.

[0214] The dispersant is ethylenediaminetetraacetic acid. When mixing the dispersant, disperse at 400 rpm for 20 min to improve dispersibility; when adding some boehmite, disperse at 2400 rpm for 30 min; when adding the remaining boehmite, disperse at 2400 rpm for 20 min.

[0215] S4. Then mix water with the insulating slurry and adjust the solid content to 10 wt%; then add a pH adjuster to a pH value of 8.5; then mix with a wetting agent (isopropanol), and after homogenization, obtain the water-based edge coating; in the water-based edge coating, the mass ratio of boehmite to modified binder is 100:25, and the mass ratio of boehmite to dispersant is 100:3;

[0216] When mixing water with the insulating slurry, disperse at 2400 rpm for 30 minutes; when mixing with the wetting agent, stir at 12 rpm for 40 minutes.

[0217] The homogenization includes two homogenizations at a pressure of 600 bar.

[0218] The pH adjuster is a sodium hydroxide solution, wherein the concentration of the sodium hydroxide solution is 0.1 mol / L.

[0219] Comparative Example 3

[0220] This comparative example provides a conventional water-based edge coating, which is identical to Example 1 except that the modified binder and other components are replaced with polyacrylic acid.

[0221] Performance Characterization

[0222] To test the sheet resistance and transmission resistance of the samples, several 20×5cm strips were taken. The surface sheet resistance of the samples was measured using a four-probe sheet resistance meter. New strips were then cut into 5×5cm smaller samples, and the transmission resistance was measured using a film resistance meter. The test data were recorded. For electrode peel force, the prepared positive electrode was attached to the test plate with 2cm 3M double-sided tape to separate the active material from the carbon coating layer. The tape was then attached to the carbon-coated aluminum foil, and the 180° electrode peel force was tested on a tensile testing machine. The results are shown in Table 1.

[0223] Table 1

[0224]

[0225] In summary, this invention introduces cyano groups into polyacrylic acid (PAA). The cyano group has a strongly electronegative single atom and a carbon-nitrogen triple bond, making it a highly polar functional group. This polarity can form stronger dipole-dipole or ion-dipole interactions with metal ions or oxygen atoms on the surface of the cathode material, thereby improving interfacial adhesion. In addition, although PAA itself forms hydrogen bonds with hydroxyl groups (-OH) on the surface of the cathode material through carboxyl groups (-COOH), after the introduction of cyano groups, the nitrogen atom of the cyano group may also participate in hydrogen bond formation (such as with -OH or residual moisture on the material surface), providing additional adhesion sites. Nano-alumina is a wide bandgap insulating material with a bandgap of approximately 8 eV to 9 eV. Its nanoparticles dispersed in the PAA matrix can directly block electron conduction paths, reducing the conductivity of the composite material. In addition, a large number of heterogeneous interfaces are formed between nano-alumina and PAA. The energy level differences at these interfaces can lead to charge accumulation (interface polarization), hindering the directional movement of electrons or ions, thus improving insulation. Uniformly dispersed nano-alumina forms a maze effect in PAA, extending the electron or ion conduction path (similar to the "zigzag path" model), significantly increasing the bulk resistance.

[0226] The applicant declares that 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 modified adhesive, characterized in that, The modified binder comprises cyano-functionalized polyacrylic acid and nano-alumina dispersed in the cyano-functionalized polyacrylic acid.

2. The modified adhesive according to claim 1, characterized in that, The mass ratio of the cyanofunctionalized polyacrylic acid to the nano-alumina is 10:1 to 100:

1.

3. A method for preparing a modified adhesive, characterized in that, The preparation method includes the following steps: A cyano group is introduced into polyacrylic acid by esterification to obtain cyano-functionalized polyacrylic acid; nano-alumina is dispersed in the cyano-functionalized polyacrylic acid by blending to obtain the modified binder according to claim 1 or 2.

4. The preparation method according to claim 3, characterized in that, The esterification reaction includes: mixing polyacrylic acid, cyaniding agent, catalyst and organic solvent, and carrying out the esterification reaction under a protective atmosphere. The resulting product is then post-treated to obtain the cyanofunctionalized polyacrylic acid.

5. The preparation method according to claim 4, characterized in that, The cyaniding agent includes any one or a combination of at least two of cyanoacetamide, cyanoacetonitrile, or cyanoethanol. And / or, the catalyst comprises any one or a combination of at least two of p-toluenesulfonic acid, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, or sulfuric acid; And / or, the organic solvent includes any one or a combination of at least two of toluene, dimethylformamide, or dimethyl sulfoxide; And / or, the mass ratio of the polyacrylic acid, cyaniding agent and organic solvent is 1:(2~3):(8~12); And / or, the amount of the catalyst used is 5% to 10% of the molar amount of the polyacrylic acid; And / or, the esterification reaction is carried out at a temperature of 110°C to 120°C; And / or, the esterification reaction takes 6 to 12 hours.

6. The preparation method according to claim 3, characterized in that, The blending method includes: surface modification of nano-alumina to obtain surface-modified alumina; dispersion of cyanofunctionalized polyacrylic acid in water to obtain PAA slurry; uniform dispersion of surface-modified alumina in the PAA slurry; and after drying and annealing, dispersion of nano-alumina in the cyanofunctionalized polyacrylic acid to obtain the modified binder. And / or, the surface modification includes surface modification of nano-alumina using ethylenediaminetetraacetic acid; And / or, the particle size Dv50 of the nano-alumina is 15nm~25nm, and the Dv90 is 90nm~110nm; And / or, the content of cyanofunctionalized polyacrylic acid in the PAA slurry is 5wt%~10wt%; And / or, the drying temperature is above 80°C and the time is above 24 hours; And / or, the annealing temperature is 100℃~150℃.

7. A water-based edge coating, characterized in that, The water-based edge coating comprises boehmite, deionized water, wetting agent, pH adjuster, dispersant, and the modified binder as described in claim 1 or 2; The mass ratio of boehmite to the modified binder is 100:(20~30); The mass ratio of boehmite to the dispersant is 100:(2~4).

8. A method for preparing a water-based edge coating, characterized in that, The preparation method includes the following steps: (1) Mix deionized water with the modified adhesive according to claim 1 or 2 to obtain an adhesive solution; (2) Mix the dispersant with the adhesive solution, and then add a portion of boehmite and the remainder of boehmite in sequence to obtain an insulating slurry; the portion of boehmite accounts for 40% to 60% of the total boehmite; (3) Then mix water with the insulating slurry and adjust the solid content to 8wt%~12wt%; then add a pH adjuster to a pH value of 8~9; then mix with a wetting agent and homogenize to obtain the water-based edge coating of claim 7.

9. The preparation method according to claim 8, characterized in that, The solid content of the adhesive solution in step (1) is 15wt%~25wt%, and the viscosity is 800mPa·s~3000mPa·s; And / or, the wetting agent includes any one or a combination of at least two of polyether siloxane, modified polyether siloxane, or alcohol reagent; And / or, the pH adjuster includes a sodium hydroxide solution; And / or, the dispersant includes ethylenediaminetetraacetic acid.

10. A side coating, characterized in that, The edge coating is obtained by applying the water-based edge coating material as described in claim 7.

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