Water-based edge paste for functional current collector, preparation method thereof and functional current collector

Abstract

This invention provides a functional current collector using an aqueous edge coating slurry, its preparation method, and the functional current collector itself. The aqueous edge coating slurry comprises an insulating main material, a solvent, functional additives, a dispersant, and a binder. The insulating main material has a core-shell structure, including boehmite particles with a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer grafted onto its surface. By grafting the poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer onto the surface of the boehmite particles, this invention improves the dispersion stability of the boehmite particles in the slurry, contributing to the acquisition of an aqueous edge coating slurry with excellent dispersibility and good stability. This aqueous edge coating slurry ensures high insulation performance and uniformity of the edge coating, improves product yield, enhances the insulation reliability of the edge coating, and guarantees the safety performance of lithium-ion batteries during long-term use.

Description

Technical Field

[0001] This invention belongs to the field of battery materials technology, specifically relating to a functional current collector with an aqueous edge coating slurry, its preparation method, and the functional current collector. Background Technology

[0002] Lithium-ion batteries (LIBs) have been widely accepted in various fields such as consumer electronics, transportation, power tools, and energy storage. Aluminum foil current collectors refer to the process of combining aluminum foil with other materials (such as paper, plastic film, coatings, etc.) to form a composite material. This technology can endow aluminum foil with new properties and functions to meet the needs of different industries. To improve the performance of lithium batteries, the lithium battery industry employs a carbon-coated current collector strategy to increase the rate of operation and overall performance. To improve the safety of lithium battery current collectors, a ceramic edge coating measure is applied to the edges of the carbon-coated current collector. Lithium-ion battery edge coating involves applying ceramic slurry to the edges of the carbon-coated current collector. This measure is of great significance to the manufacturing of lithium-ion batteries: 1. Safety: Directly reduces the risk of battery short circuits and thermal runaway, meeting the high safety standards of power batteries (such as electric vehicles). 2. Lifespan Improvement: Reduces edge side reactions (such as lithium plating and corrosion), extending cycle life. 3. High Energy Density Design: Edge protection allows for more aggressive optimization of electrode thickness or material systems. Therefore, the core purpose of carbon coating for current collector edge coating is to "eliminate edge risks and improve battery reliability and performance". It is one of the key steps in the detailed optimization of battery manufacturing, especially in high-end applications (such as power batteries and high-nickel systems).

[0003] However, while traditional edge coating designs focus on coating thickness and insulation, in practical applications, the small particle size and difficulty in dispersing insulating materials such as boehmite in the slurry often lead to poor uniformity of the edge coating. For example, traditional aqueous edge coating slurries often result in uneven coating thickness and resistance distribution due to the tendency of ultrafine boehmite particles to agglomerate, thus posing a potential threat to the battery's insulation safety. These problems manifest in two ways: first, uneven coating thickness affects the physical coverage effect; second, uneven resistance distribution leads to a decrease in local insulation performance, ultimately threatening the overall safety of the battery.

[0004] Therefore, how to effectively suppress the agglomeration of boehmite particles and ensure their uniform dispersion in the edge coating slurry, thereby ensuring that the edge coating forms a uniform and dense insulating structure on the current collector surface, is a technical problem that urgently needs to be solved. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide an aqueous edge coating slurry for a functional current collector, its preparation method, and the functional current collector itself. The present invention designs a core-shell structured insulating material, namely, grafting a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer onto the surface of boehmite particles. This copolymer layer acts as a polyelectrolyte brush, providing durable and strong steric stability in aqueous systems through steric hindrance, significantly improving the dispersion stability of boehmite particles in the slurry. This contributes to obtaining an aqueous edge coating slurry with excellent dispersibility and good stability. This aqueous edge coating slurry not only effectively ensures high insulation performance and uniformity of the edge coating, avoiding interface defects or local resistance anomalies caused by uneven coating and improving product yield, but also significantly enhances the insulation reliability of the edge coating, thereby ensuring the safety performance of lithium-ion batteries during long-term use. Furthermore, this aqueous edge coating slurry also maintains compatibility with existing current collector undercoating processes, showing promising application prospects.

[0006] To achieve this objective, the present invention adopts the following technical solution: In a first aspect, the present invention provides a functional current collector water-based edge coating slurry, the water-based edge coating slurry comprising an insulating main material, a solvent, a functional additive, a dispersant, and a binder.

[0007] The insulating material has a core-shell structure and includes boehmite particles with a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer grafted onto its surface.

[0008] This invention designs a core-shell structured insulating material, namely, grafting a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer onto the surface of boehmite particles. This copolymer layer acts as a polyelectrolyte brush, providing durable and strong steric stability in aqueous systems through steric hindrance, significantly improving the dispersion stability of boehmite particles in the slurry. This helps to obtain an aqueous edge coating slurry with excellent dispersibility and good stability. This aqueous edge coating slurry not only effectively ensures the high insulation performance and uniformity of the edge coating, avoiding interface defects or local resistance anomalies caused by uneven coating and improving product yield, but also significantly enhances the insulation reliability of the edge coating, thereby ensuring the safety performance of lithium-ion batteries during long-term use. In addition, this aqueous edge coating slurry also takes into account compatibility with existing current collector undercoating processes, showing good application prospects.

[0009] Preferably, the grafting rate of the boehmite particles is 150-250%, for example, it can be 150%, 200% or 250%.

[0010] In this invention, the grafting rate of boehmite particles is as high as 150-250%, which is much higher than the structural design of simply adsorbing polymers onto the surface. This indicates that a core-shell structure can be formed with the help of boehmite particles with a high grafting rate, rather than a surface coating. It also indicates that the dispersion stability has been significantly improved, and that it has stronger interfacial bonding and flexibility.

[0011] It should be noted that the grafting rate refers to the percentage of the mass of the polymer that is successfully bonded to the surface of the material through chemical bonds, relative to the mass of the matrix material. It determines the thickness and density of the surface modification.

[0012] Preferably, based on the total dry weight of the water-based edge coating slurry, the amount of the main insulating material added is 50-80%, for example, it can be 50%, 60%, 70% or 80%.

[0013] In this invention, the amount of insulating main material added is limited to 50-80%, which can ensure the insulation and density of the coating.

[0014] Preferably, based on the total dry weight of the water-based edge coating slurry, the mass content of the adhesive is 20-50%, for example, it can be 20%, 30%, 40% or 50%, etc.

[0015] In this invention, by limiting the mass content of the adhesive, the adhesion and insulation of the coating made from the slurry can be balanced.

[0016] Preferably, the dry basis mass ratio of the insulating main material to the dispersant is 100:(0.5-2), for example, it can be 100:0.5, 100:1, 100:1.5 or 100:2, etc.

[0017] In this invention, by limiting the ratio of the insulating main material to the dispersant, the dispersibility of the insulating main material in the slurry can be significantly improved, and the agglomeration phenomenon in the slurry can be reduced.

[0018] Preferably, the dispersant comprises ethylenediaminetetraacetic acid.

[0019] Preferably, the functional additive includes a wetting agent, and the amount of the wetting agent added is 5-15% of the total mass of the water-based edge coating slurry, for example, it can be 5%, 10% or 15%.

[0020] In this invention, the appropriate amount of wetting agent can fully regulate the surface tension of the slurry, which is beneficial to the diffusion and leveling of the slurry.

[0021] Preferably, the wetting agent comprises isopropanol.

[0022] Preferably, the solid content of the water-based edge coating slurry is 8-12%, for example, it can be 8%, 9%, 10%, 11% or 12%, etc.

[0023] In a second aspect, the present invention provides a method for preparing a functional current collector water-based edge coating slurry as described in the first aspect, the preparation method comprising the following steps; Prepare the main insulating material.

[0024] The insulating main material, functional additives, dispersant, binder and solvent are mixed to obtain the functional current collector water-based edge coating slurry.

[0025] The preparation method provided by this invention is simple in process, low in production cost and low in maintenance cost, and meets the comprehensive requirements of lithium-ion batteries for edge coating insulation performance and safety standards, which is conducive to its widespread use.

[0026] Preferably, the preparation steps of the insulating main material include: (a) Boehmite is acidified to obtain acidified boehmite.

[0027] (b) The acidified boehmite, silane coupling agent and solvent are mixed and silanized to obtain modified boehmite with carbon-carbon double bonds on the surface.

[0028] (c) The modified boehmite with carbon-carbon double bonds on its surface, acrylic acid, poly(2-acrylamido-2-methyl-1-propanesulfonic acid), initiator and solvent are mixed and subjected to in-situ graft copolymerization to obtain the insulating main material.

[0029] In this invention, the mechanism of acidification is explained as follows: 1) Under acidic conditions, boehmite has a strong positive charge on its surface, making it environmentally stable and less susceptible to the influence of CO2 in the air. Even if a small amount of CO2 dissolves to form carbonic acid, it has little impact on the pH value and overall charge of the system, and the dispersion stability can be maintained for a long time; 2) Boehmite is relatively stable in acidic aqueous solutions, does not easily undergo phase transitions or dissolve, and can maintain its crystal structure. It should be noted that acidification is mainly a physicochemical process of surface protonation, which has little impact on the material itself; 3) In the subsequent slightly acidic in-situ polymerization system, the molecular chains of carboxyl-containing monomers such as acrylic acid are coiled due to protonation. These coiled polymer chains can be more effectively adsorbed onto the particle surface, providing strong steric stabilization. Combined with continuous electrostatic repulsion, this ultimately ensures the dispersion stability of boehmite in the slurry; 4) The purpose of acidification is not only to disperse but also to increase the density and reactivity of surface hydroxyl groups.

[0030] In this invention, the purpose of the silanization reaction is to introduce "anchoring points" and reaction sites, building a robust, covalently linked "bridge" between boehmite and the silane coupling agent. The specific mechanism is as follows: The surface of boehmite particles is rich in aluminum hydroxyl groups (Al-OH). The methoxy group (-OCH3) in the silane coupling agent, such as KH-570, reacts with water or water molecules adsorbed on the boehmite surface to generate active silanol (-SiOH). The generated silanol then undergoes a dehydration condensation reaction with the Al-OH groups on the boehmite surface to form a strong Si-O-Al covalent bond. Finally, the other end of the silane coupling agent, such as KH-570, namely the methacryloyloxy group with a carbon-carbon double bond (C=C), is permanently fixed on the surface of the boehmite. This carbon-carbon double bond is the starting point for the subsequent in-situ graft copolymerization reaction.

[0031] In this invention, the purpose of the in-situ graft copolymerization reaction is to grow a "polymer brush," that is, starting from the carbon-carbon double bonds on the surface of boehmite, the polymer chains are "grown" from the surface of boehmite like a brush through free radical polymerization. The mechanism is as follows: sulfate radical anions are generated by the decomposition of the initiator. These free radicals attack the carbon-carbon double bonds on the surface of boehmite. Since the carbon-carbon double bonds are covalently connected to the surface, the free radicals actually generate "initiation centers" on the surface of the boehmite particles. The monomers acrylic acid and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) move freely in the reaction system. They diffuse to the "initiation centers" on the surface of the boehmite particles and react with them, causing the polymer chains to grow continuously. Since the "initiation center" is on the surface of the boehmite particles, the in-situ graft copolymerization reaction proceeds from the particle surface into the solution, which can be called a bridging strategy. Its grafting density and efficiency are much higher than simply adsorbing the prepared polymer onto the surface. Therefore, the copolymerized acrylic acid provides carboxyl groups (-COOH), and poly(2-acrylamide-2-methyl-1-propanesulfonic acid) provides highly polar sulfonate groups. The two copolymerize to form long, randomly arranged copolymer chains with a large number of hydrophilic functional groups, thereby constructing a three-dimensional, soft shell on the surface of the boehmite. Finally, boehmite particles with a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer grafted on the surface are obtained, which are boehmite-g-Poly (AAc-co-AMPS) hybrid materials with a core-shell structure.

[0032] Preferably, during the acidification process in step (a), the pH of the system is 3-4, for example, it can be 3, 3.2, 3.4, 3.6, 3.8 or 4.

[0033] This invention limits the pH of the system to the range of 3-4 during the acidification process. Essentially, it finds a balance between various physical properties: within this range, boehmite can carry the strongest positive charge and is easy to disperse, the silane coupling agent can be moderately hydrolyzed without self-condensation, and the boehmite particles themselves will not dissolve.

[0034] Preferably, the surface hydroxyl groups of the acidified boehmite are activated before mixing the acidified boehmite, silane coupling agent, and solvent.

[0035] In this invention, the purpose of activating the surface hydroxyl groups of acidified boehmite is to increase and expose reactive hydroxyl sites on the surface of boehmite through acid treatment, thereby providing high-density covalent bonding anchors for subsequent grafting processes, and ultimately achieving high grafting rate and high stability.

[0036] Preferably, the silane coupling agent in step (b) includes any one or a combination of at least two of KH570, KH550 or vinyltriethoxysilane.

[0037] Preferably, the amount of the silane coupling agent is 8-12% of the mass of the acidified boehmite, for example, it can be 8%, 9%, 10%, 11% or 12%, etc.

[0038] Preferably, the atmosphere for the silanization reaction in step (b) is an inert atmosphere. For example, it could be nitrogen or argon.

[0039] Preferably, the temperature of the silanization reaction in step (b) is 40-80°C, for example, 40°C, 50°C, 60°C, 70°C or 80°C, and the time is 10-15h, for example, 10h, 11h, 12h, 13h, 14h or 15h.

[0040] In this invention, the silanization reaction is carried out under suitable process parameters in order to form a dense, uniform active double bond layer on the surface of boehmite that is connected only by covalent bonds, thus laying the foundation for subsequent high-density, high-stability polymer brush grafting.

[0041] Preferably, the amount of acrylic acid used in step (c) is 45-55% of the mass of the modified boehmite, for example, it can be 45%, 50% or 55% etc.

[0042] Preferably, the molar ratio of acrylic acid and poly(2-acrylamide-2-methyl-1-propanesulfonic acid) in step (c) is (0.8-1.2):(0.8-1.2), wherein the range of acrylic acid “0.8-1.2” can be, for example, 0.8, 0.9, 1, 1.1 or 1.2, and the range of poly(2-acrylamide-2-methyl-1-propanesulfonic acid) “0.8-1.2” can be, for example, 0.8, 0.9, 1, 1.1 or 1.2.

[0043] Preferably, during the in-situ graft copolymerization reaction in step (c), the pH of the system is 7-8, for example, it can be 7, 7.2, 7.4, 7.6, 7.8 or 8.

[0044] This invention limits the pH of the system to the range of 7-8 during the in-situ graft copolymerization reaction, which can optimize the decomposition efficiency of the initiator, maintain system stability, and prevent flocculation.

[0045] Preferably, the temperature of the in-situ graft copolymerization reaction in step (c) is 60-80°C, for example, 60°C, 70°C or 80°C, and the time is 5-7h, for example, 5h, 6h or 7h.

[0046] In this invention, in-situ graft copolymerization can be carried out under suitable process parameters to achieve high-density grafting of the surface; the polymer chain conformation is optimized to maximize steric hindrance.

[0047] Preferably, the preparation method includes the following steps: (1) Preparation of insulating main material: (1-1) Under stirring conditions, boehmite powder was added to deionized water, and then acid solution was added to adjust the pH of the slurry to 3-4. After standing and drying, acidified boehmite was obtained.

[0048] (1-2) The acidified boehmite is added to an acid solution with a pH of 3.5-4.5 (e.g., 3.5, 4 or 4.5) and subjected to ultrasonic treatment to disperse the acidified boehmite and activate the surface hydroxyl groups to obtain a suspension; the suspension is washed with water and alcohol to obtain a boehmite wet cake.

[0049] The boehmite wet cake was dispersed in an alcohol solution, and then a silane coupling agent solution was added. The reaction was carried out at 40-80°C under an inert atmosphere and with continuous stirring for 10-15 hours. After the reaction was completed, the mixture was cooled, the solid was collected, washed and dried to obtain modified boehmite with carbon-carbon double bonds on its surface. The amount of the silane coupling agent was 8-12% of the mass of the acidified boehmite.

[0050] (1-3) The modified boehmite with carbon-carbon double bonds on its surface is added to deionized water to form a suspension. Then, acrylic acid and poly(2-acrylamide-2-methyl-1-propanesulfonic acid) are added sequentially, and a pH adjuster is added under stirring to make the pH of the system 7-8. Then, an initiator (exemplarily, such as ammonium persulfate) is added to the reaction system, and an in-situ graft copolymerization reaction is carried out at 60-80°C, under an inert atmosphere and with continuous stirring for 5-7 hours. After the reaction is completed, the mixture is purified and collected to obtain the insulating main material. The amount of acrylic acid is 45-55% of the mass of the modified boehmite. The molar ratio of acrylic acid to poly(2-acrylamide-2-methyl-1-propanesulfonic acid) is (0.8-1.2):(0.8-1.2).

[0051] (2) Under stirring conditions, deionized water and dispersant are mixed, and then the insulating main material is added in three steps. Then, deionized water is added to adjust the solid content of the slurry to 10-15% (for example, it can be 10%, 11%, 12%, 13%, 14% or 15%) to obtain the water-based edge coating slurry semi-finished product.

[0052] The dispersant includes any one or a combination of at least two of ethylenediaminetetraacetic acid, citric acid, or polyethylene glycol; the stirring rate for mixing the deionized water and the dispersant is 1000-1200 rpm (e.g., 1000 rpm, 1100 rpm, or 1200 rpm); the amount of the main insulating material added in the first step accounts for 1 / 4 of the total mass of the main insulating material, the amount added in the second step accounts for 1 / 4 of the total mass of the main insulating material, and the amount added in the third step accounts for 1 / 2 of the total mass of the main insulating material; the stirring rate for each of the three steps of adding the main insulating material is independently 2000-2600 rpm (e.g., 2000 rpm, 2200 rpm, 2400 rpm, or 2600 rpm); the stirring rate when adding deionized water to adjust the solid content of the slurry is 2000-2600 rpm (e.g., 2000 rpm, 2200 rpm, 2400 rpm, or 2600 rpm).

[0053] (3) Under stirring conditions of 1200-1500 rpm (e.g., 1200 rpm, 1300 rpm, 1400 rpm, or 1500 rpm, etc.), a binder is added, and then a wetting agent is added under stirring conditions of 40-60 rpm (e.g., 40 rpm, 50 rpm, or 60 rpm, etc.). Finally, homogenization is performed to obtain a functional manifold water-based edge coating slurry; wherein, the binder includes polyacrylic acid. The adhesive solution has a solid content of 15-25 wt% (e.g., 15 wt%, 20 wt%, or 25 wt%) and a viscosity of 800-3000 mPa·s (e.g., 800 mPa·s, 1000 mPa·s, 1500 mPa·s, 2000 mPa·s, 2500 mPa·s, or 3000 mPa·s); the wetting agent includes any one or a combination of at least two of isopropanol, tert-butanol, or isobutanol.

[0054] Thirdly, the present invention provides a functional current collector, the functional current collector including a current collector body, wherein an active region for which an active material layer is disposed is reserved on at least one side of the surface of the current collector body; at least one edge coating is disposed at at least one end position of the active region along the horizontal direction of the functional current collector.

[0055] The raw materials for preparing the edge coating include the water-based edge coating slurry for functional current collectors as described in the first aspect.

[0056] For example, an edge coating is provided at both ends of the active region along the horizontal direction of the functional current collector.

[0057] For example, the functional current collector may be a carbon-coated current collector, etc.

[0058] Fourthly, the present invention provides a lithium-ion battery, the lithium-ion battery comprising an electrode sheet, the electrode sheet comprising a functional current collector as described in the third aspect and an active material layer disposed in the active region.

[0059] Preferably, the thickness of the edge coating on one side is 0.5-2μm, for example, it can be 0.5μm, 1.5μm or 2μm.

[0060] 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.

[0061] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention designs a core-shell structured insulating material, namely, grafting a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer onto the surface of boehmite particles. This copolymer layer, acting as a polyelectrolyte brush, provides a durable and strong steric stabilization effect in aqueous systems through steric hindrance, significantly improving the dispersion stability of boehmite particles in the slurry. This helps to obtain an aqueous edge coating slurry with excellent dispersibility and good stability. This aqueous edge coating slurry not only effectively ensures the high insulation performance and uniformity of the edge coating, avoiding interface defects or local resistance abnormalities caused by uneven coating, thus improving product yield, but also significantly enhances the insulation reliability of the edge coating, thereby ensuring the safety performance of lithium-ion batteries during long-term use. In addition, this aqueous edge coating slurry also takes into account compatibility with existing current collector undercoating processes, showing good application prospects.

[0062] (2) The preparation method provided by the present invention is simple, has low production cost and low maintenance cost, and meets the comprehensive requirements of lithium-ion batteries for edge coating insulation performance and safety standards, which is conducive to its widespread use. Detailed Implementation

[0063] 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 in any way.

[0064] It should be noted that the main materials used in the following embodiments include: ① Nitric acid, purchased from Sinopharm Group, model AR (Shanghai Trial), 65.0-68.0%, 500mL, Sinopharm code 10014518; ② Boehmite, purchased from Sinopharm Group, model 3.4µm (Wokai), 500g, Sinopharm code XW01131823603; ③ KH570, purchased from Sinopharm Group, model KH 570 (Shanghai Trial), 5kg, Sinopharm code 3021387511; ④ Acrylic acid, purchased from Sinopharm Group, model AR (Shanghai Trial), ≥99.0%, 500mL, Sinopharm code 80001418; ⑤ Poly(2-acrylamido-2-methyl-1-propanesulfonic acid), purchased from Sinopharm Group, model Acros-184965000 500g of ammonium persulfate (C184965000), purchased from Sinopharm Group, model AR (Shanghai Testing), ≥98.0%, 500g, Sinopharm Group code 10002618; 7. Anhydrous ethanol (AR, ≥99.7%), purchased from Sinopharm Group, model AR (Shanghai Testing), ≥99.7%, 500mL, Sinopharm Group code 10009218; 8. Ammonia (LC-MS), ≥25% (Wokai), 100mL, Sinopharm Group code XW011336216024; 9. Deionized water; 10. Isopropanol (LC-MS), 4L, Sinopharm Group code 40064361; 3. Polyacrylic acid adhesive (7002), purchased from Linte Technology; 4. Ethylenediaminetetraacetic acid (EDTA), purchased from Sinopharm Group, model AR (Shanghai Testing), ≥99.0%. 25kg, National Drug Code 100096193.

[0065] Example 1 This embodiment provides a functional current collector water-based edge coating slurry, which includes an insulating main material, a solvent, a wetting agent, a dispersant, and a binder.

[0066] The insulating material has a core-shell structure and includes boehmite particles with a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer grafted onto the surface; the grafting rate of the boehmite particles is 250%.

[0067] Specifically, based on the total dry weight of the water-based edge coating slurry, the amount of the main insulating material added is 73.5%; based on the total dry weight of the water-based edge coating slurry, the mass content of the binder is 25%; the dry weight ratio of the main insulating material to the dispersant is 100:2; the amount of the wetting agent added is 10% of the total mass of the water-based edge coating slurry; the solid content of the water-based edge coating slurry is 10%; the binder is polyacrylic acid, the dispersant is ethylenediaminetetraacetic acid, the wetting agent is isopropanol, and the solvent is deionized water.

[0068] This embodiment also provides a method for preparing the above-mentioned functional manifold water-based edge coating slurry, the preparation method comprising the following steps: (1) Preparation of insulating main material: (1-1) Under stirring conditions of 1500 rpm, boehmite powder was slowly added to deionized water, and then nitric acid solution with a concentration of 3 mol / L was added dropwise to adjust the pH of the slurry to between 3 and 4. After standing and drying, acidified boehmite was obtained.

[0069] (1-2) Add 5g of the acidified boehmite to 200mL of dilute nitric acid solution with pH 4 and sonicate for 30min to disperse the acidified boehmite and activate the surface hydroxyl groups to obtain a suspension; centrifuge the suspension at 8000rpm for 10min to remove the supernatant, then wash it three times with deionized water until the supernatant is neutral, and then wash it twice with anhydrous ethanol to obtain a wet boehmite cake.

[0070] The boehmite wet cake was dispersed in 150 mL of anhydrous ethanol and transferred to a 250 mL three-necked flask. The three-necked flask was placed in a 60 °C water bath, equipped with a condenser and a nitrogen delivery tube, and a magnetic stirrer was turned on. Nitrogen gas was introduced for protection and continued for 20 min to remove air from the system. Then, a silane coupling agent solution, consisting of 0.5 g of silane coupling agent KH570 and 20 mL of anhydrous ethanol, was slowly added dropwise to the three-necked flask using a constant pressure dropping funnel, with the addition time controlled at approximately 30 min. After the addition was complete, the flask was heated at 60 °C under nitrogen. The silanization reaction was carried out for 12 hours under an atmospheric and continuously stirred condition. After the reaction, the mixture was naturally cooled to room temperature (25°C), and then centrifuged at 8000 rpm for 10 minutes. The solid was collected and washed repeatedly with anhydrous ethanol until the supernatant was colorless and transparent to ensure the removal of all physically adsorbed silanes. Finally, the product was dried in a vacuum drying oven at 60°C and ground to obtain modified boehmite with carbon-carbon double bonds on the surface. The amount of the silane coupling agent KH570 was 10% of the mass of the acidified boehmite.

[0071] (1-3) Place 2g of the modified boehmite with carbon-carbon double bonds on its surface into a 250mL three-necked flask, add 100mL of deionized water, and sonicate for 30min to form a suspension; then add 1g of acrylic acid and 2.9g of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) sequentially, and slowly add ammonia water dropwise under stirring to adjust the pH of the system to 7-8; purge with nitrogen for 30min to remove oxygen from the system; then rapidly inject 0.04g of ammonium persulfate solution (5mL in deionized water) into the reaction system through a dropping funnel, and stir continuously at 70℃ under nitrogen atmosphere. Under stirring conditions, an in-situ graft copolymerization reaction was carried out for 6 hours. After the reaction, the product was transferred to a dialysis bag and dialyzed in 2L of deionized water. The water was changed every 5 hours and dialysis was continued for several days until no sulfate ions were detected in the water outside the dialysis bag using silver nitrate solution. Then, the purified product, namely the aqueous dispersion of Poly(AAc-co-AMPS) grafted boehmite nanohybrid material, was collected and freeze-dried to obtain the solid powder of the insulating main material. The amount of acrylic acid used was 50% of the mass of the modified boehmite. The molar ratio of acrylic acid to poly(2-acrylamide-2-methyl-1-propanesulfonic acid) was 1:1.

[0072] (2) Deionized water and ethylenediaminetetraacetic acid were stirred and dispersed in a 200L double star mixing tank at 1100 rpm for 20 min. Then, the first batch of insulation material, accounting for 1 / 4 of the total mass of the main insulation material, was added and stirred and dispersed in a 200L double star mixing tank at 2300 rpm for 10 min. Then, the second batch of insulation material, accounting for 1 / 4 of the total mass of the main insulation material, was added and stirred and dispersed in a 200L double star mixing tank at 2300 rpm for 30 min. Then, the third batch of insulation material, accounting for 1 / 2 of the total mass of the main insulation material, was added and stirred and dispersed in a 200L double star mixing tank at 2300 rpm for 60 min. Finally, an appropriate amount of deionized water was added to adjust the solid content of the slurry to 15%, and stirred and dispersed at 2300 rpm for 30 min to obtain the semi-finished water-based edge coating slurry.

[0073] (3) Add polyacrylic acid liquid to the semi-finished water-based edge coating slurry and disperse it for 30 min under stirring at 1350 rpm. Then add isopropanol and disperse it for 30 min under stirring at 50 rpm. Finally, perform two homogenization treatments in a homogenizer at 600 bar to obtain a functional current collector water-based edge coating slurry. The solid content of the polyacrylic acid liquid is 20 wt%, and the viscosity is 2000 mPa·s.

[0074] This embodiment also provides a functional current collector, which includes a current collector body, and active regions with active material layers are reserved on both sides of the current collector body. An edge coating is provided at both ends of the active regions along the horizontal direction of the functional current collector. The raw materials for preparing the edge coating include the water-based edge coating slurry for the functional current collector as described above.

[0075] The current collector body is a carbon-coated current collector; the thickness of the edge coating on one side is 2μm; and the width of the edge coating on one side is 300mm.

[0076] Example 2 The difference between this embodiment and embodiment 1 is that steps (2) and (3) are replaced with the following steps: (2') Deionized water and ethylenediaminetetraacetic acid were stirred and dispersed in a 200L double-star mixing tank at 1000 rpm for 20 min. Then, 1 / 4 of the total mass of the main insulating material was added and stirred and dispersed in the 200L double-star mixing tank at 2000 rpm for 10 min. Then, 1 / 4 of the total mass of the main insulating material was added and stirred and dispersed in the 200L double-star mixing tank at 2000 rpm for 30 min. Then, 1 / 2 of the total mass of the main insulating material was added and stirred and dispersed in the 200L double-star mixing tank at 2000 rpm for 60 min. Finally, an appropriate amount of deionized water was added to adjust the solid content of the slurry and stirred and dispersed at 2000 rpm for 30 min to obtain the semi-finished water-based edge coating slurry.

[0077] (3') Add polyacrylic acid liquid to the semi-finished water-based edge coating slurry and disperse it for 30 min under stirring at 1200 rpm. Then add isopropanol and disperse it for 30 min under stirring at 40 rpm. Finally, perform two homogenization treatments in a homogenizer at 600 bar to obtain a functional current collector water-based edge coating slurry. The polyacrylic acid liquid has a solid content of 15 wt% and a viscosity of 1000 mPa·s.

[0078] The remaining preparation methods and parameters are consistent with those in Example 1.

[0079] Example 3 The difference between this embodiment and embodiment 1 is that steps (2) and (3) are replaced with the following steps: (2') Deionized water and ethylenediaminetetraacetic acid were stirred and dispersed in a 200L double-star mixing tank at 1200rpm for 20min. Then, 1 / 4 of the total mass of the main insulating material was added and stirred and dispersed in the 200L double-star mixing tank at 2600rpm for 10min. Then, 1 / 4 of the total mass of the main insulating material was added and stirred and dispersed in the 200L double-star mixing tank at 2600rpm for 30min. Then, 1 / 2 of the total mass of the main insulating material was added and stirred and dispersed in the 200L double-star mixing tank at 2600rpm for 60min. Finally, an appropriate amount of deionized water was added to adjust the solid content of the slurry and stirred and dispersed at 2600rpm for 30min to obtain the semi-finished water-based edge coating slurry.

[0080] (3') Add polyacrylic acid liquid to the semi-finished water-based edge coating slurry and disperse it for 30 min under stirring at 1500 rpm. Then add isopropanol and disperse it for 30 min under stirring at 60 rpm. Finally, perform two homogenization treatments in a homogenizer at 600 bar to obtain a functional current collector water-based edge coating slurry. The polyacrylic acid liquid has a solid content of 25 wt% and a viscosity of 3000 mPa·s.

[0081] The remaining preparation methods and parameters are consistent with those in Example 1.

[0082] Example 4 The difference between this embodiment and Embodiment 1 is that, based on the total dry weight of the water-based edge coating slurry, the amount of the main insulating material added is 60%.

[0083] The remaining preparation methods and parameters are consistent with those in Example 1.

[0084] Example 5 The difference between this embodiment and Embodiment 1 is that, based on the total dry weight of the water-based edge coating slurry, the amount of the main insulating material added is 50%.

[0085] The remaining preparation methods and parameters are consistent with those in Example 1.

[0086] Example 6 The difference between this embodiment and Embodiment 1 is that the dry basis mass ratio of the insulating main material to the dispersant is 100:1.

[0087] The remaining preparation methods and parameters are consistent with those in Example 1.

[0088] Example 7 The difference between this embodiment and Embodiment 1 is that the dry basis mass ratio of the insulating main material to the dispersant is 100:0.5.

[0089] The remaining preparation methods and parameters are consistent with those in Example 1.

[0090] Example 8 The difference between this embodiment and Embodiment 1 is that the amount of KH570 is adjusted so that the grafting rate on the surface of the boehmite particles is 100%.

[0091] The remaining preparation methods and parameters are consistent with those in Example 1.

[0092] Example 9 The difference between this embodiment and Embodiment 1 is that, based on the total dry weight of the water-based edge coating slurry, the amount of the main insulating material added is 40%.

[0093] The remaining preparation methods and parameters are consistent with those in Example 1.

[0094] Example 10 The difference between this embodiment and Embodiment 1 is that, based on the total dry weight of the water-based edge coating slurry, the amount of the main insulating material added is 85%.

[0095] The remaining preparation methods and parameters are consistent with those in Example 1.

[0096] Example 11 The difference between this embodiment and Embodiment 1 is that the dry basis mass ratio of the insulating main material to the dispersant is 100:2.5.

[0097] The remaining preparation methods and parameters are consistent with those in Example 1.

[0098] Example 12 The difference between this embodiment and Embodiment 1 is that the dry basis mass ratio of the insulating main material to the dispersant is 100:0.2.

[0099] The remaining preparation methods and parameters are consistent with those in Example 1.

[0100] Example 13 The difference between this embodiment and embodiment 1 is that in step (2), the insulating main material is added in one step.

[0101] The remaining preparation methods and parameters are consistent with those in Example 1.

[0102] Comparative Example 1 The difference between this comparative example and Example 1 is that step (1) is not performed, that is, the boehmite particles are not surface grafted.

[0103] The remaining preparation methods and parameters are consistent with those in Example 1.

[0104] Comparative Example 2 The difference between this comparative example and Example 1 is that no dispersant is added.

[0105] The remaining preparation methods and parameters are consistent with those in Example 1.

[0106] Performance testing The sheet resistance and transmission resistance of the functional current collectors provided in the above embodiments and comparative examples were tested. The test steps included: taking a sample strip with a length and width of 20×5cm, testing the surface sheet resistance of the sample strip using a four-probe sheet resistance meter, then cutting the new sample strip into small samples of 5×5cm, testing the transmission resistance under a diaphragm resistance meter, and recording the test data.

[0107] The test results are shown in Table 1.

[0108] Table 1 analyze: As shown in Table 1, the present invention designs a core-shell structured insulating material, namely, grafting a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer onto the surface of boehmite particles. This copolymer layer, acting as a polyelectrolyte brush, provides a durable and strong steric stabilization effect in aqueous systems through steric hindrance, significantly improving the dispersion stability of boehmite particles in the slurry. This helps to obtain an aqueous edge coating slurry with excellent dispersibility and good stability. This aqueous edge coating slurry not only effectively ensures the high insulation performance and uniformity of the edge coating, avoiding interface defects or local resistance abnormalities caused by uneven coating, thus improving product yield, but also significantly enhances the insulation reliability of the edge coating, thereby ensuring the safety performance of lithium-ion batteries during long-term use. The resulting functional current collector has an infinite sheet resistance and a penetration resistance of up to 200kΩ.

[0109] As can be seen from the comparison between Example 1 and Example 8, if the grafting rate on the surface of boehmite particles is too low, the polymer brush cannot form a dense and thick coating layer. The steric hindrance effect is insufficient, which leads to the easy agglomeration of boehmite particles in the slurry. In the end, the thickness of the edge coating is uneven, the resistance distribution is uneven, and the insulation performance is reduced.

[0110] As can be seen from the comparison between Example 1 and Examples 9-10, if the amount of insulating main material added is too small, the insulating components in the coating will be insufficient, and a continuous and effective insulating network cannot be formed, resulting in low resistance; if the amount of insulating main material added is too large, the viscosity of the slurry will be out of control, the dispersion will be difficult, the coating will become more brittle and prone to cracking, and economic costs will be wasted.

[0111] As can be seen from the comparison between Example 1 and Examples 11-12, if the dry basis mass ratio of the insulating material to the dispersant is too large, it cannot effectively coat the particle surface, resulting in insufficient steric hindrance and electrostatic repulsion, and the particles are prone to secondary agglomeration. If the dry basis mass ratio of the insulating material to the dispersant is too small, it will be free in the slurry, which will aggravate agglomeration. Moreover, the excess dispersant may migrate to the coating surface after drying, causing contamination.

[0112] As can be seen from the comparison between Example 1 and Example 13, if the insulating material is added in step (2) in one step, the local concentration will be too high at the moment, the probability of collision between particles will increase dramatically, and the dispersant and mechanical force will not have time to act on each new surface, which will easily lead to the agglomeration of particles to form large-diameter agglomerates, and uniform dispersion cannot be achieved.

[0113] As can be seen from the comparison between Example 1 and Comparative Example 1, if the boehmite particles are not surface grafted, that is, conventional boehmite is used as the main insulating material, the surface of the boehmite lacks a polymer brush that is compatible with the system. The oleophilic and hydrophobic surface is prone to agglomeration in water and cannot form chain entanglement with the binder, resulting in a large number of defects in the coating and extremely low insulation resistance.

[0114] As can be seen from the comparison between Example 1 and Comparative Example 2, if no dispersant is added, even if there is surface-grafted boehmite, the lack of small molecule dispersant to assist in anchoring and charge stabilization will result in poor long-term storage stability of the slurry. The particles will slowly settle under gravity and form hard precipitates, leading to uneven composition and decreased resistance during coating.

[0115] It should be noted that the present invention is illustrated through the above embodiments, but the present invention is not limited to the above process steps, that is, it does not mean that the present invention must rely on the above process steps to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions of the raw materials used in the present invention, additions of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A functional manifold water-based edge coating slurry, characterized in that, The water-based edge coating slurry includes insulating main material, solvent, functional additives, dispersant and binder; The insulating material has a core-shell structure and includes boehmite particles with a poly(acrylic acid-co-2-acrylamide-2-methylpropanesulfonic acid) copolymer layer grafted onto its surface.

2. The functional manifold water-based edge coating slurry according to claim 1, characterized in that, The grafting rate on the surface of the boehmite particles is 150-250%.

3. The functional manifold water-based edge coating slurry according to claim 1, characterized in that, Based on the total dry weight of the water-based edge coating slurry, the amount of the main insulating material added is 50-80%; And / or, based on the total dry weight of the water-based edge coating slurry, the mass content of the binder is 20-50%; And / or, the dry basis mass ratio of the insulating main material to the dispersant is 100:(0.5-2); And / or, the functional additive includes a wetting agent, wherein the amount of the wetting agent added is 5-15% of the total mass of the water-based edge coating slurry; And / or, the solid content of the water-based edge coating slurry is 8-12%.

4. A method for preparing a functional manifold water-based edge coating slurry as described in any one of claims 1-3, characterized in that, The preparation method Includes the following steps; Preparation of insulating main materials; The insulating main material, functional additives, dispersants, binders and solvents are mixed to obtain the functional current collector water-based edge coating slurry.

5. The preparation method according to claim 4, characterized in that, The preparation steps of the insulating main material include: (a) Acidification treatment of boehmite to obtain acidified boehmite; (b) The acidified boehmite, silane coupling agent and solvent are mixed and silanized to obtain modified boehmite with carbon-carbon double bonds on the surface. (c) The modified boehmite with carbon-carbon double bonds on its surface, acrylic acid, poly(2-acrylamido-2-methyl-1-propanesulfonic acid), initiator and solvent are mixed and subjected to in-situ graft copolymerization to obtain the insulating main material.

6. The preparation method according to claim 5, characterized in that, During the acidification process described in step (a), the pH of the system is 3-4; And / or, the surface hydroxyl groups of the acidified boehmite are activated before the acidified boehmite, silane coupling agent and solvent are mixed.

7. The preparation method according to claim 5, characterized in that, The silane coupling agent in step (b) includes any one or a combination of at least two of KH570, KH550 or vinyltriethoxysilane; And / or, the amount of the silane coupling agent is 8-12% of the mass of the acidified boehmite; And / or, the atmosphere of the silanization reaction in step (b) is an inert atmosphere; And / or, the silanization reaction in step (b) is carried out at a temperature of 40-80°C for a time of 10-15 h.

8. The preparation method according to claim 5, characterized in that, In step (c), the amount of acrylic acid used is 45-55% of the mass of the modified boehmite; And / or, the molar ratio of acrylic acid and poly(2-acrylamido-2-methyl-1-propanesulfonic acid) in step (c) is (0.8-1.2):(0.8-1.2); And / or, during the in-situ graft copolymerization reaction described in step (c), the pH of the system is 7-8; And / or, the in-situ graft copolymerization reaction in step (c) is carried out at a temperature of 60-80°C for 5-7 hours.

9. The preparation method according to claim 4, characterized in that, The preparation method includes the following steps: (1) Preparation of insulating main material: (1-1) Under stirring conditions, boehmite powder was added to deionized water, then acid solution was added to adjust the pH of the slurry to 3-4, and the mixture was allowed to stand and dried to obtain acidified boehmite. (1-2) The acidified boehmite is added to an acidic solution with a pH of 3.5-4.5 and subjected to ultrasonic treatment to disperse the acidified boehmite and activate the surface hydroxyl groups to obtain a suspension; the suspension is washed with water and alcohol to obtain a boehmite wet cake. The boehmite wet cake was dispersed in an alcohol solution, and then a silane coupling agent solution was added. A silanization reaction was carried out at 40-80°C under an inert atmosphere and with continuous stirring for 10-15 hours. After the reaction was completed, the mixture was cooled, the solid was collected, washed, and dried to obtain modified boehmite with carbon-carbon double bonds on its surface. The amount of the silane coupling agent was 8-12% of the mass of the acidified boehmite. (1-3) The modified boehmite with carbon-carbon double bonds on its surface is added to deionized water to form a suspension. Then, acrylic acid and poly(2-acrylamide-2-methyl-1-propanesulfonic acid) are added sequentially, and a pH adjuster is added under stirring to make the pH of the system 7-8. Subsequently, an initiator is added to the reaction system, and an in-situ graft copolymerization reaction is carried out at 60-80°C, under an inert atmosphere and with continuous stirring for 5-7 hours. After the reaction is completed, the mixture is purified and collected to obtain the insulating main material. The amount of acrylic acid is 45-55% of the mass of the modified boehmite. The molar ratio of acrylic acid to poly(2-acrylamide-2-methyl-1-propanesulfonic acid) is (0.8-1.2):(0.8-1.2). (2) Under stirring conditions, deionized water and dispersant are mixed, and then added to the main insulating material in three steps. Then, deionized water is added to adjust the solid content of the slurry to 10-15% to obtain a semi-finished water-based edge coating slurry. The dispersant includes any one or a combination of at least two of ethylenediaminetetraacetic acid, citric acid, or polyethylene glycol; the stirring rate for mixing the deionized water and the dispersant is 1000-1200 rpm; the amount of the main insulating material added in the first step accounts for 1 / 4 of the total mass of the main insulating material, the amount added in the second step accounts for 1 / 4 of the total mass of the main insulating material, and the amount added in the third step accounts for 1 / 2 of the total mass of the main insulating material; the stirring rate for each of the three steps of adding the main insulating material is independently 2000-2600 rpm; the stirring rate when adding deionized water to adjust the solid content of the slurry is 2000-2600 rpm. (3) Add a binder to the semi-finished water-based edge coating slurry under stirring conditions of 1200-1500 rpm, then add a wetting agent under stirring conditions of 40-60 rpm, and finally perform homogenization treatment to obtain a functional manifold water-based edge coating slurry; wherein, the binder includes polyacrylic acid liquid, the solid content of the polyacrylic acid liquid is 15-25 wt%, and the viscosity is 800-3000 mPa·s; the wetting agent includes any one or a combination of at least two of isopropanol, tert-butanol or isobutanol.

10. A functional current collector, characterized in that, The functional current collector includes a current collector body, and an active region for which an active material layer is provided is reserved on at least one side of the surface of the current collector body; at least one edge coating is provided at at least one end position of the active region along the horizontal direction of the functional current collector. The raw materials for preparing the edge coating include the functional current collector water-based edge coating slurry as described in any one of claims 1-3.

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