Aqueous adhesive for carbon-coated aluminum foil of lithium-ion batteries and preparation method thereof

Abstract

This invention discloses an aqueous binder for carbon-coated aluminum foil of lithium-ion batteries and its preparation method, relating to the field of lithium-ion battery binder technology. The aqueous binder comprises the following components: modified glucose, conductive composite particles, glutaraldehyde, sodium carboxymethyl cellulose, sodium polyacrylate, and deionized water. The preparation method involves sequentially adding sodium polyacrylate and conductive composite particles to deionized water and stirring until homogeneous; then adding modified glucose and sodium carboxymethyl cellulose and continuing to stir until homogeneous; finally adding glutaraldehyde and stirring to react, thus obtaining the aqueous binder for carbon-coated aluminum foil of lithium-ion batteries. This invention uses renewable biomass glucose as the main raw material, combined with water as a solvent, eliminating the need for organic solvents. The production process is pollution-free, and the raw materials are biodegradable, making it green and environmentally friendly.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery binder technology, specifically to an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries and its preparation method. Background Technology

[0002] With the rapid development of the lithium-ion battery industry, carbon-coated aluminum foil, as a key material for improving battery energy density and cycle stability, plays a decisive role in the overall performance of the battery. As a core component of carbon-coated aluminum foil, the performance of the binder directly affects the bonding effect between the electrode material and the current collector.

[0003] Currently, most binders used in the market for carbon-coated aluminum foil in lithium-ion batteries are solvent-based binders, such as polyvinylidene fluoride (PVDF). These binders typically require organic solvents such as N-methylpyrrolidone (NMP) for dissolution and dispersion. NMP is not only toxic and poses a potential health threat to operators, but its high boiling point and difficulty in recycling lead to high energy consumption and increased costs in the production process. Furthermore, the volatilization of organic solvents causes serious environmental pollution, which is inconsistent with the trend of green and environmentally friendly development. In addition, solvent-based binders pose flammable and explosive safety hazards during use, increasing the difficulty of risk management in the production process.

[0004] In recent years, the deepening development of environmental protection concepts has led to a gradual increase in research on water-based binders in the industry. However, existing water-based binders still have many problems. Some water-based binders use a large amount of non-degradable polymers in pursuit of bonding performance, which are difficult to decompose naturally after the battery is scrapped, thus causing environmental pollution. Other water-based binders, although they use biodegradable components, have poor overall performance and cannot meet the performance requirements of binders for carbon-coated aluminum foil in lithium-ion batteries.

[0005] Glucose, as a widely available biomass material, boasts environmental advantages such as renewability, biodegradability, and good biocompatibility. Its application in the field of carbon-coated aluminum foil binders for lithium-ion batteries can solve the environmental problems associated with traditional binders. However, glucose itself has extremely poor conductivity, failing to effectively promote electron transport between the electrode material and the current collector. This makes it difficult to meet the requirement that binders for carbon-coated aluminum foil must possess good conductivity to reduce interfacial resistance and improve battery charge-discharge performance. Summary of the Invention

[0006] The purpose of this invention is to provide an aqueous binder for carbon-coated aluminum foil of lithium-ion batteries and its preparation method, so as to solve the technical problems mentioned in the background art, namely, the lack of environmental protection of existing binders and the poor conductivity of glucose binders.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A water-based binder for carbon-coated aluminum foil for lithium-ion batteries, comprising the following components in parts by weight:

[0009] Modified glucose 40-60 parts, conductive composite particles 10-20 parts, glutaraldehyde 3-6 parts, sodium carboxymethyl cellulose 1-3 parts, sodium polyacrylate 0.5-1 parts, water 50-80 parts.

[0010] In this invention, glucose is selected as the main component of the binder. Glucose, as a widely available biomass material, has environmental advantages such as being renewable, biodegradable, and biocompatible. Furthermore, water is used as the solvent, making it green and environmentally friendly. Conductive composite particles can improve the conductivity of the binder and reduce the electrode interface impedance. Glutaraldehyde, as a crosslinking agent, has two aldehyde groups that can react with active groups such as hydroxyl groups in the modified glucose molecule to form a three-dimensional network structure within the binder system. This crosslinking structure enhances the cohesive force and mechanical strength of the binder. Sodium carboxymethyl cellulose, as a thickener, is readily soluble in water and can effectively adjust the viscosity of the binder, improve rheological properties, and ensure good workability during coating. It can be uniformly coated on the aluminum foil surface, avoiding sagging and accumulation, and also stabilizes the dispersion of the conductive composite particles in the binder, preventing sedimentation. Sodium polyacrylate, acting as a dispersant, is adsorbed onto the surface of conductive composite particles. Through electrostatic repulsion and steric hindrance, it effectively prevents the aggregation of conductive composite particles. The uniformly dispersed conductive composite particles not only facilitate the construction of a continuous and efficient conductive network, but also ensure the uniformity of the properties of each part of the binder, avoiding localized degradation of conductivity or coating defects caused by particle aggregation.

[0011] Preferably, the method for preparing the modified glucose includes the following steps:

[0012] (1) Prepare a glucose solution, then add aniline to the glucose solution and stir under heating conditions to obtain an aniline-modified glucose solution;

[0013] (2) Melamine was added to the aniline-modified glucose solution, and the mixture was heated and stirred to react. After the reaction was completed, the solution was distilled under reduced pressure to remove excess water and small molecule impurities to obtain modified glucose.

[0014] In the technical solution of this invention, as described above, environmentally friendly aqueous glucose is used as a binder. However, glucose itself has extremely poor conductivity and cannot effectively promote electron transport between the electrode material and the current collector. Therefore, this invention modifies glucose. Aniline molecules contain amino groups, while glucose molecules contain multiple hydroxyl groups. Under certain conditions, aniline and glucose undergo a nucleophilic substitution reaction. The amino group of aniline acts as a nucleophile, attacking the carbon atom attached to the hydroxyl group in the glucose molecule. The hydroxyl group is removed in the form of water, and the amino group replaces the hydroxyl group, thereby introducing the conjugated structure of aniline into the glucose molecule. Since the π electrons in the conjugated structure can be delocalized throughout the entire conjugated system, exhibiting good electron mobility, this gives the modified glucose molecule a certain electron transport capability, creating conditions for improving the conductivity of the binder. Melamine molecules contain multiple amino groups. In addition to the retained hydroxyl groups, the newly introduced conjugated structure in aniline-modified glucose molecules also possesses certain reactivity. Under heating conditions, the amino groups of melamine undergo a condensation reaction with the hydroxyl groups or active sites on the conjugated structure of the aniline-modified glucose molecules. During the reaction, water molecules are removed between the amino and hydroxyl groups, forming new chemical bonds that attach melamine to the aniline-modified glucose molecules. The introduction of melamine not only increases the molecular weight and spatial complexity of the glucose molecules, but its nitrogen-containing functional groups can also combine with the functional groups on the surface of subsequently added conductive composite particles through hydrogen bonds or other intermolecular forces, enhancing the bonding force between the binder matrix and the conductive particles, further optimizing the electron transport path, and synergistically improving the conductivity of the binder.

[0015] Preferably, in step (1), glucose is dissolved in water to prepare a glucose solution, and the amount of aniline added is 10-15% of the glucose mass.

[0016] Preferably, in step (2), the amount of melamine added is 3-8% of the glucose mass.

[0017] Preferably, the method for preparing the conductive composite particles includes the following steps:

[0018] (a) Carbon nanotubes and graphene are mixed to obtain hybrid particles;

[0019] (b) The mixed particles are acidified to introduce carboxyl functional groups on the surface of the mixed particles. After the acidification is completed, the conductive particles are repeatedly washed with water until neutral and then dried to obtain pretreated conductive particles.

[0020] (c) Add polyaniline to N-methylpyrrolidone and stir to dissolve, prepare a polyaniline solution, add the pretreated conductive particles to the polyaniline solution, heat and stir to react, so that the polyaniline is coated on the surface of the pretreated conductive particles to obtain conductive composite particles.

[0021] In this invention, the conductivity of the binder is improved in two ways. First, as mentioned above, the conductivity of the glucose matrix is ​​modified to initially improve the conductivity of the binder. Second, the conductivity of the binder is further improved by adding conductive composite particles. Through the synergistic effect of these two aspects, the binder exhibits excellent conductivity. The specific preparation method of the conductive composite particles involves first selecting a mixture of carbon nanotubes and graphene as conductive particles, then acidifying them with nitric acid solution to introduce functional groups such as carboxyl groups onto their surface, increasing the surface activity of the conductive particles. Then, polyaniline is used to coat them. Polyaniline itself is a conductive polymer material with good conductivity. The coated polyaniline not only conducts electricity itself but also builds additional conductive bridges between the conductive particles, increasing the number of conductive pathways between the particles and enabling electrons to be transported between them more efficiently. Meanwhile, the polyaniline coating can also improve the compatibility and bonding force between the conductive particles and the binder matrix (modified glucose), enabling the conductive particles to be better dispersed in the binder, avoiding the aggregation of conductive particles, thereby maintaining a stable and efficient conductive network and significantly improving the conductivity of the binder.

[0022] Preferably, in step (a), the mass ratio of carbon nanotubes to graphene is 3:0.5-2.

[0023] Preferably, in step (b), the acidification treatment refers to adding the mixed particles to a nitric acid solution for acidification treatment, wherein the mass concentration of the nitric acid solution is 5-10%.

[0024] Preferably, in step (c), the heating reaction temperature is 70°C and the reaction time is 6 hours.

[0025] Preferably, the mass ratio of the pretreated conductive particles to polyaniline is 10:1-3.

[0026] In the technical solution of this invention, as described above, coating conductive particles with polyaniline increases the number of conductive pathways between the particles, enabling electrons to transfer more efficiently between them and improving the conductivity of the binder. To achieve the above technical effect, sufficient polyaniline must be coated on the surface of the conductive particles. Therefore, this invention controls the mass ratio of pretreated conductive particles to polyaniline to be less than 10 / 1. However, the invention team unexpectedly discovered that as the amount of polyaniline continued to increase, when the mass ratio of pretreated conductive particles to polyaniline was less than 10 / 3, the flexibility of the binder after curing and drying suddenly decreased significantly. During the charging and discharging process of lithium-ion batteries, the electrode material undergoes volume expansion and contraction, requiring the binder to have good flexibility to adapt to this change; otherwise, the binder is prone to cracking, affecting the service life of the electrode material. The above phenomenon may be due to the rigid structure of the polyaniline molecular chain. When excessive polyaniline coats the surface of conductive particles, a large number of rigid polyaniline molecules form a thick and rigid coating layer around the conductive particles. This rigid coating layer restricts the relative movement and deformation ability between conductive particles and between the conductive particles and the binder matrix, thus leading to a decrease in the flexibility of the binder. Therefore, to balance the conductivity and flexibility of the binder, this invention controls the mass ratio of pretreated conductive particles to polyaniline within the range of 10:1-3.

[0027] A method for preparing an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries includes the following steps:

[0028] Sodium polyacrylate and conductive composite particles are added to water in sequence and stirred until homogeneous. Then, modified glucose and sodium carboxymethyl cellulose are added and stirred until homogeneous. Finally, glutaraldehyde is added and stirred to react, thus obtaining a water-based binder for carbon-coated aluminum foil for lithium-ion batteries.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. Using renewable biomass glucose as the main raw material and water as the solvent, eliminating organic solvents, the production process is pollution-free, and the raw materials are biodegradable, making it green and environmentally friendly;

[0031] 2. By synergistically enhancing the effects of modified glucose and conductive composite particles, the conductivity of the binder is significantly improved, and the application and dispersibility of various additives are optimized to ensure stable battery performance;

[0032] 3. Control the amount of polyaniline coating on the surface of conductive particles to avoid excessive polyaniline leading to a decrease in flexibility, and achieve a balance between the conductivity and flexibility of the adhesive. Detailed Implementation

[0033] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0034] The main raw material specifications and related suppliers used in the specific embodiments are as follows:

[0035] Glucose: Analytical grade (≥99.5%), Shandong Lukang; Aniline: Analytical grade (≥99.5%), Sinopharm Chemical Reagent; Melamine: Industrial grade (≥99%), white powder (C3H6N6), Sichuan Meifeng; Carbon nanotubes: Diameter 10-20 nm, length 10-30 μm, purity >95%, Jiangsu Tiannai; Graphene: Sheet size 0.5-5 μm, thickness 1-5 nm, Ningbo Moxi; Sodium carboxymethyl cellulose: High viscosity type (degree of substitution 0.6), battery grade (no metal impurities), Ashland Chemical; Sodium polyacrylate: Low molecular weight (2000-5000), Jiangsu Fumiao Technology.

[0036] Example 1

[0037] A water-based binder for carbon-coated aluminum foil for lithium-ion batteries, comprising the following components in parts by weight:

[0038] 55 parts modified glucose, 18 parts conductive composite particles, 5 parts glutaraldehyde, 2.5 parts sodium carboxymethyl cellulose, 0.9 parts sodium polyacrylate, and 75 parts deionized water.

[0039] Preparation of modified glucose:

[0040] (1) Weigh 50g of glucose and place it in a 500mL beaker. Add 400mL of deionized water and stir with a magnetic stirrer until completely dissolved to prepare a glucose solution. Weigh 7g of aniline and slowly add it to the glucose solution. Place the beaker in a digital display constant temperature water bath, heat it to 80℃, and stir at 300r / min for 3 hours to obtain an aniline-modified glucose solution.

[0041] (2) Weigh 3.5g of melamine and add it to the above aniline-modified glucose solution. Raise the water bath temperature to 90℃ and continue stirring at 300r / min for 4 hours. After the reaction is complete, transfer the solution to a rotary evaporator and distill under reduced pressure at -0.09MPa and 60℃ to remove excess water and small molecule impurities, and obtain modified glucose.

[0042] Preparation of conductive composite particles:

[0043] (a) Weigh 30g of carbon nanotubes and 18g of graphene, place them in a clean and dry mortar, and grind and mix them thoroughly for 10 minutes to obtain mixed particles;

[0044] (b) Prepare a 7% (w / w) 500 mL nitric acid solution. Add the mixed particles to the nitric acid solution and place the mixture in a 60 °C water bath. Stir and acidify at 250 rpm for 2 hours. After acidification, use a Buchner funnel and a vacuum filter to repeatedly wash the particles with deionized water until the pH of the washing solution is approximately 7. Transfer the washed particles to a vacuum drying oven and dry at 80 °C for 12 hours to obtain pretreated conductive particles.

[0045] (c) Weigh 10g of pretreated conductive particles and 2.5g of polyaniline. Add the polyaniline to 200mL of N-methylpyrrolidone and stir with an electric stirrer at 400r / min until completely dissolved to prepare a polyaniline solution. Add the pretreated conductive particles to the polyaniline solution and place it in a 70℃ water bath. Stir at 350r / min for 6 hours. After the reaction is complete, separate by centrifugation (4000r / min, 10 minutes), wash with appropriate amounts of N-methylpyrrolidone and deionized water sequentially, and finally dry in a 60℃ vacuum drying oven for 8 hours to obtain conductive composite particles.

[0046] A method for preparing an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries includes the following steps:

[0047] Deionized water was added to a beaker, followed by sodium polyacrylate and conductive composite particles. The mixture was stirred with an electric stirrer at 350 rpm for 15 minutes until uniformly dispersed. Modified glucose and sodium carboxymethyl cellulose were then added, and stirring continued for 20 minutes. Finally, glutaraldehyde was added, and the mixture was stirred for 1 hour to obtain an aqueous binder for carbon-coated aluminum foil used in lithium-ion batteries.

[0048] Example 2

[0049] A water-based binder for carbon-coated aluminum foil for lithium-ion batteries, comprising the following components in parts by weight:

[0050] 45 parts modified glucose, 12 parts conductive composite particles, 4 parts glutaraldehyde, 1.5 parts sodium carboxymethyl cellulose, 0.7 parts sodium polyacrylate, and 60 parts deionized water.

[0051] Preparation of modified glucose:

[0052] (1) Weigh 50g of glucose and place it in a 500mL beaker. Add 400mL of deionized water and stir with a magnetic stirrer until completely dissolved to prepare a glucose solution. Weigh 5.5g of aniline and slowly add it to the glucose solution. Place the beaker in a digital display constant temperature water bath, heat it to 80℃, and stir at 300r / min for 3 hours to obtain an aniline-modified glucose solution.

[0053] (2) Weigh 2g of melamine and add it to the above aniline-modified glucose solution. Raise the water bath temperature to 90℃ and continue stirring at 300r / min for 4 hours. After the reaction is complete, transfer the solution to a rotary evaporator and distill under reduced pressure at -0.09MPa and 60℃ to remove excess water and small molecule impurities, and obtain modified glucose.

[0054] Preparation of conductive composite particles:

[0055] (a) Weigh 30g of carbon nanotubes and 10g of graphene, place them in a clean and dry mortar, and grind and mix them thoroughly for 10 minutes to obtain mixed particles;

[0056] (b) Prepare a 7% (w / w) 500 mL nitric acid solution. Add the mixed particles to the nitric acid solution and place the mixture in a 60 °C water bath. Stir and acidify at 250 rpm for 2 hours. After acidification, use a Buchner funnel and a vacuum filter to repeatedly wash the particles with deionized water until the pH of the washing solution is approximately 7. Transfer the washed particles to a vacuum drying oven and dry at 80 °C for 12 hours to obtain pretreated conductive particles.

[0057] (c) Weigh 10g of pretreated conductive particles and 1.5g of polyaniline. Add the polyaniline to 200mL of N-methylpyrrolidone and stir with an electric stirrer at 400r / min until completely dissolved to prepare a polyaniline solution. Add the pretreated conductive particles to the polyaniline solution and place it in a 70℃ water bath. Stir at 350r / min for 6 hours. After the reaction is complete, separate by centrifugation (4000r / min, 10 minutes), wash with appropriate amounts of N-methylpyrrolidone and deionized water sequentially, and finally dry in a 60℃ vacuum drying oven for 8 hours to obtain conductive composite particles.

[0058] A method for preparing an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries includes the following steps:

[0059] Deionized water was added to a beaker, followed by sodium polyacrylate and conductive composite particles. The mixture was stirred with an electric stirrer at 350 rpm for 15 minutes until uniformly dispersed. Modified glucose and sodium carboxymethyl cellulose were then added, and stirring continued for 20 minutes. Finally, glutaraldehyde was added, and the mixture was stirred for 1 hour to obtain an aqueous binder for carbon-coated aluminum foil used in lithium-ion batteries.

[0060] Example 3

[0061] A water-based binder for carbon-coated aluminum foil for lithium-ion batteries, comprising the following components in parts by weight:

[0062] 50 parts modified glucose, 15 parts conductive composite particles, 4.5 parts glutaraldehyde, 2 parts sodium carboxymethyl cellulose, 0.8 parts sodium polyacrylate, and 65 parts deionized water.

[0063] Preparation of modified glucose:

[0064] (1) Weigh 50g of glucose and place it in a 500mL beaker. Add 400mL of deionized water and stir with a magnetic stirrer until completely dissolved to prepare a glucose solution. Weigh 6g of aniline and slowly add it to the glucose solution. Place the beaker in a digital display constant temperature water bath, heat it to 80℃, and stir at 300r / min for 3 hours to obtain an aniline-modified glucose solution.

[0065] (2) Weigh 2.5g of melamine and add it to the above aniline-modified glucose solution. Raise the water bath temperature to 90℃ and continue stirring at 300r / min for 4 hours. After the reaction is complete, transfer the solution to a rotary evaporator and distill under reduced pressure at -0.09MPa and 60℃ to remove excess water and small molecule impurities, and obtain modified glucose.

[0066] Preparation of conductive composite particles:

[0067] (a) Weigh 30g of carbon nanotubes and 10g of graphene, place them in a clean and dry mortar, and grind and mix them thoroughly for 10 minutes to obtain mixed particles;

[0068] (b) Prepare a 7% (w / w) 500 mL nitric acid solution. Add the mixed particles to the nitric acid solution and place the mixture in a 60 °C water bath. Stir and acidify at 250 rpm for 2 hours. After acidification, use a Buchner funnel and a vacuum filter to repeatedly wash the particles with deionized water until the pH of the washing solution is approximately 7. Transfer the washed particles to a vacuum drying oven and dry at 80 °C for 12 hours to obtain pretreated conductive particles.

[0069] (c) Weigh 10g of pretreated conductive particles and 2g of polyaniline. Add the polyaniline to 200mL of N-methylpyrrolidone and stir with an electric stirrer at 400r / min until completely dissolved to prepare a polyaniline solution. Add the pretreated conductive particles to the polyaniline solution and place it in a 70℃ water bath. Stir at 350r / min for 6 hours. After the reaction is complete, separate by centrifugation (4000r / min, 10 minutes), wash with appropriate amounts of N-methylpyrrolidone and deionized water sequentially, and finally dry in a 60℃ vacuum drying oven for 8 hours to obtain conductive composite particles.

[0070] A method for preparing an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries includes the following steps:

[0071] Deionized water was added to a beaker, followed by sodium polyacrylate and conductive composite particles. The mixture was stirred with an electric stirrer at 350 rpm for 15 minutes until uniformly dispersed. Modified glucose and sodium carboxymethyl cellulose were then added, and stirring continued for 20 minutes. Finally, glutaraldehyde was added, and the mixture was stirred for 1 hour to obtain an aqueous binder for carbon-coated aluminum foil used in lithium-ion batteries.

[0072] Example 4

[0073] A water-based binder for carbon-coated aluminum foil for lithium-ion batteries, comprising the following components in parts by weight:

[0074] 60 parts modified glucose, 20 parts conductive composite particles, 6 parts glutaraldehyde, 3 parts sodium carboxymethyl cellulose, 1 part sodium polyacrylate, and 80 parts deionized water.

[0075] Preparation of modified glucose:

[0076] (1) Weigh 50g of glucose and place it in a 500mL beaker. Add 400mL of deionized water and stir with a magnetic stirrer until completely dissolved to prepare a glucose solution. Weigh 7.5g of aniline and slowly add it to the glucose solution. Place the beaker in a digital display constant temperature water bath, heat it to 80℃, and stir at 300r / min for 3 hours to obtain an aniline-modified glucose solution.

[0077] (2) Weigh 4g of melamine and add it to the above aniline-modified glucose solution. Raise the water bath temperature to 90℃ and continue stirring at 300r / min for 4 hours. After the reaction is complete, transfer the solution to a rotary evaporator and distill under reduced pressure at -0.09MPa and 60℃ to remove excess water and small molecule impurities, and obtain modified glucose.

[0078] Preparation of conductive composite particles:

[0079] (a) Weigh 30g of carbon nanotubes and 20g of graphene, place them in a clean and dry mortar, and grind and mix them thoroughly for 10 minutes to obtain mixed particles;

[0080] (b) Prepare a 10% (w / w) 500 mL nitric acid solution. Add the mixed particles to the nitric acid solution and place the mixture in a 60 °C water bath. Stir and acidify at 250 rpm for 2 hours. After acidification, use a Buchner funnel and a vacuum filter to repeatedly wash the particles with deionized water until the pH of the washing solution is approximately 7. Transfer the washed particles to a vacuum drying oven and dry at 80 °C for 12 hours to obtain pretreated conductive particles.

[0081] (c) Weigh 10g of pretreated conductive particles and 3g of polyaniline. Add the polyaniline to 200mL of N-methylpyrrolidone and stir with an electric stirrer at 400r / min until completely dissolved to prepare a polyaniline solution. Add the pretreated conductive particles to the polyaniline solution and place it in a 70℃ water bath. Stir at 350r / min for 6 hours. After the reaction is complete, separate by centrifugation (4000r / min, 10 minutes), wash with appropriate amounts of N-methylpyrrolidone and deionized water sequentially, and finally dry in a 60℃ vacuum drying oven for 8 hours to obtain conductive composite particles.

[0082] A method for preparing an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries includes the following steps:

[0083] Deionized water was added to a beaker, followed by sodium polyacrylate and conductive composite particles. The mixture was stirred with an electric stirrer at 350 rpm for 15 minutes until uniformly dispersed. Modified glucose and sodium carboxymethyl cellulose were then added, and stirring continued for 20 minutes. Finally, glutaraldehyde was added, and the mixture was stirred for 1 hour to obtain an aqueous binder for carbon-coated aluminum foil used in lithium-ion batteries.

[0084] Example 5

[0085] A water-based binder for carbon-coated aluminum foil for lithium-ion batteries, comprising the following components in parts by weight:

[0086] 40 parts modified glucose, 10 parts conductive composite particles, 3 parts glutaraldehyde, 1 part sodium carboxymethyl cellulose, 0.5 parts sodium polyacrylate, and 50 parts deionized water.

[0087] Preparation of modified glucose:

[0088] (1) Weigh 50g of glucose and place it in a 500mL beaker. Add 400mL of deionized water and stir with a magnetic stirrer until completely dissolved to prepare a glucose solution. Weigh 5g of aniline and slowly add it to the glucose solution. Place the beaker in a digital display constant temperature water bath, heat it to 80℃, and stir at 300r / min for 3 hours to obtain an aniline-modified glucose solution.

[0089] (2) Weigh 1.5g of melamine and add it to the above aniline-modified glucose solution. Raise the water bath temperature to 90℃ and continue stirring at 300r / min for 4 hours. After the reaction is complete, transfer the solution to a rotary evaporator and distill under reduced pressure at -0.09MPa vacuum and 60℃ to remove excess water and small molecule impurities, and obtain modified glucose.

[0090] Preparation of conductive composite particles:

[0091] (a) Weigh 30g of carbon nanotubes and 5g of graphene, place them in a clean and dry mortar, and grind and mix them thoroughly for 10 minutes to obtain mixed particles;

[0092] (b) Prepare a 5% (w / w) 500 mL nitric acid solution. Add the mixed particles to the nitric acid solution and place the mixture in a 60 °C water bath. Stir and acidify at 250 rpm for 2 hours. After acidification, use a Buchner funnel and a vacuum filter to repeatedly wash the particles with deionized water until the pH of the washing solution is approximately 7. Transfer the washed particles to a vacuum drying oven and dry at 80 °C for 12 hours to obtain pretreated conductive particles.

[0093] (c) Weigh 10g of pretreated conductive particles and 1g of polyaniline. Add the polyaniline to 200mL of N-methylpyrrolidone and stir with an electric stirrer at 400r / min until completely dissolved to prepare a polyaniline solution. Add the pretreated conductive particles to the polyaniline solution and place it in a 70℃ water bath. Stir at 350r / min for 6 hours. After the reaction is complete, separate by centrifugation (4000r / min, 10 minutes), wash with appropriate amounts of N-methylpyrrolidone and deionized water sequentially, and finally dry in a 60℃ vacuum drying oven for 8 hours to obtain conductive composite particles.

[0094] A method for preparing an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries includes the following steps:

[0095] Deionized water was added to a beaker, followed by sodium polyacrylate and conductive composite particles. The mixture was stirred with an electric stirrer at 350 rpm for 15 minutes until uniformly dispersed. Modified glucose and sodium carboxymethyl cellulose were then added, and stirring continued for 20 minutes. Finally, glutaraldehyde was added, and the mixture was stirred for 1 hour to obtain an aqueous binder for carbon-coated aluminum foil used in lithium-ion batteries.

[0096] Comparative Example 1

[0097] The difference between Comparative Example 1 and Example 1 is that the modified glucose is replaced with ordinary glucose, while the other steps are the same.

[0098] Comparative Example 2

[0099] The difference between Comparative Example 2 and Example 1 is that conductive composite particles are not added to the adhesive component, while the other steps are the same.

[0100] Comparative Example 3

[0101] The difference between Comparative Example 3 and Example 1 is that the conductive composite particles are not coated with polyaniline, while the other steps are the same.

[0102] Comparative Example 4

[0103] The difference between Comparative Example 4 and Example 4 is that in the preparation process of conductive composite particles, the mass ratio of pretreated conductive particles to polyaniline is 10:4, while the other steps are the same.

[0104] Comparative Example 5

[0105] The difference between Comparative Example 5 and Example 4 is that in the preparation process of conductive composite particles, the mass ratio of pretreated conductive particles to polyaniline is 10:5, while the other steps are the same.

[0106] Performance testing:

[0107] 1. Conductivity test:

[0108] The four-probe method was used for testing. A water-based adhesive was uniformly applied to the clean surface of the lithium-ion battery-coated aluminum foil to form a coating approximately 0.1 mm thick. The coating was then dried in a vacuum oven at 80°C for 12 hours to allow the adhesive to fully cure. The aluminum foil with the cured coating was placed on the test stage of the four-probe tester, and the four probes were adjusted to maintain close contact with the coating surface and remain perpendicular. The test current was set to 10 mA, and the resistance value displayed on the tester was read. The resistivity of the coating was calculated using the formula, with the test area fixed at 1 cm². 2 Each sample was tested three times, and the average value was taken as the final result. The lower the resistivity, the better the conductivity of the adhesive. The test results are shown in Table 1.

[0109] 2. Flexibility test:

[0110] The flexibility of the adhesive was evaluated using a bending test. Aluminum foil coated with and cured with the water-based adhesive was cut into strips of 20mm × 100mm and tested using a flexibility tester. One end of the aluminum foil was fixed to the fixture of the tester, and pressure was applied to the other end via a robotic arm, causing the foil to bend around a 3mm diameter cylinder at a bending speed of 1 bend / second. During the bending process, a high-definition camera was used to observe the surface condition of the adhesive coating in real time, recording the number of bends at which the coating first cracked or peeled off. If no obvious defects appeared in the coating after 200 bends, the flexibility was considered good. Each sample was tested 3 times, and the minimum value was taken as the result. The test results are shown in Table 1.

[0111] 3. Bond strength test:

[0112] The bond strength was tested using a universal tensile testing machine. Aluminum foil coated with water-based adhesive was cut into strips of 25mm × 50mm and bonded to another aluminum foil of the same size within a 25mm × 25mm area using the adhesive. The strips were then cured at room temperature for 48 hours. The bonded samples were clamped in the tensile testing machine fixtures, ensuring proper clamping and uniform force distribution. The tensile speed was set to 5mm / min, and the machine was started. Tensile testing continued until the bond interface failed, and the maximum tensile force at failure was recorded. The bond strength was calculated using the formula. Each sample was tested three times, and the average value was taken. The test results are shown in Table 1.

[0113] Table 1:

[0114]

[0115] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A water-based adhesive for carbon-coated aluminum foil in lithium-ion batteries, characterized in that, Includes the following components in parts by weight: Modified glucose 40-60 parts, conductive composite particles 10-20 parts, glutaraldehyde 3-6 parts, sodium carboxymethyl cellulose 1-3 parts, sodium polyacrylate 0.5-1 parts, water 50-80 parts; The method for preparing the modified glucose includes the following steps: (1) Prepare a glucose solution, then add aniline to the glucose solution and stir under heating conditions to obtain an aniline-modified glucose solution; (2) Melamine was added to the aniline-modified glucose solution, and the mixture was heated and stirred to react. After the reaction was completed, the solution was distilled under reduced pressure to remove excess water and small molecule impurities to obtain modified glucose. The method for preparing the conductive composite particles includes the following steps: (a) Carbon nanotubes and graphene are mixed to obtain hybrid particles; (b) The mixed particles are acidified to introduce carboxyl functional groups on the surface of the mixed particles. After the acidification is completed, the conductive particles are repeatedly washed with water until neutral and then dried to obtain pretreated conductive particles. (c) Add polyaniline to N-methylpyrrolidone and stir to dissolve, prepare a polyaniline solution, add the pretreated conductive particles to the polyaniline solution, heat and stir to react, so that the polyaniline is coated on the surface of the pretreated conductive particles to obtain conductive composite particles.

2. The water-based adhesive for carbon-coated aluminum foil for lithium-ion batteries according to claim 1, characterized in that, In step (1), glucose is dissolved in water to prepare a glucose solution, and the amount of aniline added is 10-15% of the glucose mass.

3. The water-based adhesive for carbon-coated aluminum foil for lithium-ion batteries according to claim 1, characterized in that, In step (2), the amount of melamine added is 3-8% of the glucose mass.

4. The water-based adhesive for carbon-coated aluminum foil for lithium-ion batteries according to claim 1, characterized in that, In step (a), the mass ratio of carbon nanotubes to graphene is 3:0.5-2.

5. The water-based adhesive for carbon-coated aluminum foil for lithium-ion batteries according to claim 1, characterized in that, In step (b), the acidification treatment refers to adding the mixed particles to a nitric acid solution for acidification, wherein the mass concentration of the nitric acid solution is 5-10%.

6. The water-based adhesive for carbon-coated aluminum foil for lithium-ion batteries according to claim 1, characterized in that, In step (c), the heating reaction temperature is 70°C and the reaction time is 6 hours.

7. The water-based adhesive for carbon-coated aluminum foil for lithium-ion batteries according to claim 6, characterized in that, The mass ratio of the pretreated conductive particles to polyaniline is 10:1-3.

8. A method for preparing an aqueous binder for carbon-coated aluminum foil for lithium-ion batteries as described in any one of claims 1-7, characterized in that, Includes the following steps: Sodium polyacrylate and conductive composite particles are added to water in sequence and stirred until homogeneous. Then, modified glucose and sodium carboxymethyl cellulose are added and stirred until homogeneous. Finally, glutaraldehyde is added and stirred to react, thus obtaining a water-based binder for carbon-coated aluminum foil for lithium-ion batteries.

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