A two-component acrylate water-based adhesive for sodium-ion battery hard carbon negative electrode and a preparation method and application thereof

Abstract

This application relates to the field of sodium-ion battery adhesives, and more particularly to a two-component aqueous acrylate adhesive for sodium-ion battery hard carbon anodes, its preparation method, and its application. The two-component aqueous acrylate adhesive for sodium-ion battery hard carbon anodes comprises 40-70 parts of a first acrylic polymer and 30-60 parts of a second acrylic polymer. The preparation method of this application, through a specific combination of the first and second acrylic polymers and a specific preparation process, results in an adhesive with excellent dispersibility, high cohesive strength, and excellent flexibility. This adhesive effectively solves the problem of limited performance in existing adhesives, improves the bonding strength and flexibility between the hard carbon anode material and the electrode sheet, enhances the initial coulombic efficiency, and reduces impedance, thereby improving the performance and stability of the electrode.

Description

Technical Field

[0001] This application relates to the field of sodium-ion battery adhesives, and more particularly to a two-component acrylate-based aqueous adhesive for sodium-ion battery hard carbon negative electrode, its preparation method, and its application. Background Technology

[0002] Sodium-ion batteries, as a novel energy storage device, have attracted increasing attention for their anode materials. Hard carbon materials are widely used as anodes in sodium-ion batteries due to their high capacity and good rate performance. However, the small particle size and numerous pores of hard carbon materials result in a large specific surface area and low compaction density, posing challenges to electrode fabrication. Currently, commonly used hard carbon anode binders, such as the CMC+SBR combination, while flexible, have limited adsorption and dispersion effects on hard carbon materials. Furthermore, the point-connection method of SBR makes it difficult for hard carbon particles to form a strong bond, easily leading to electrode "powdering." While acrylate-based waterborne binders offer good dispersibility and high cohesive strength, making "powdering" less likely, their high hardness can cause the electrode to crack during processing, making it difficult to achieve high compaction density.

[0003] Therefore, it is necessary to develop a new type of adhesive to solve the problems of poor dispersibility, insufficient cohesive strength and poor flexibility of existing adhesives in the application of hard carbon anode materials for sodium-ion batteries, so as to meet the comprehensive requirements of high dispersibility, high cohesive strength and good flexibility of hard carbon anode materials for sodium-ion batteries. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this application provides a two-component aqueous acrylate binder for sodium-ion battery hard carbon anodes, its preparation method, and its application. The aqueous acrylate binder for sodium-ion battery hard carbon anodes prepared in this application combines excellent dispersibility, high cohesive strength, and excellent flexibility, solving the problem of limited performance in existing binders. The second hydrophobic monomer possesses a relatively low glass transition temperature, and the resulting second acrylic polymer ensures the binder maintains high adhesion while exhibiting relatively more flexible mechanical properties. The second acrylic polymer significantly enhances the affinity and compatibility between the aqueous binder and the hard carbon anode material, improves the bonding strength and flexibility between the hard carbon anode material and the electrode sheet, increases the initial coulombic efficiency, and reduces impedance, thereby improving the electrode's performance and stability. Furthermore, the preparation method of this application is simple and easy to implement, suitable for large-scale production.

[0005] In a first aspect, this application provides a two-component acrylate-based aqueous binder for hard carbon anodes in sodium-ion batteries, employing the following technical solution:

[0006] A two-component acrylate-based aqueous binder for sodium-ion battery hard carbon anodes, comprising 100 parts by total mass, is prepared from the following raw materials: 40-70 parts of a first acrylate polymer and 30-60 parts of a second acrylate polymer. The first acrylate polymer is prepared by: using a polymer with the chemical formula CH2=CR... 1 COOM's first hydrophilic monomer has the chemical formula R. 2 CH=CHR 3 The first hydrophobic monomer of CN and deionized water are added to a reaction flask, stirred, and nitrogen is purged to remove oxygen. The water bath temperature is raised to 70-80℃, and then the first water-soluble initiator solution is added dropwise. After the addition is complete, the reaction is continued at a constant temperature for 4-10 hours. The reaction is then stopped by cooling, and the product is discharged when the temperature drops below 40℃ to obtain the first acrylic polymer. The preparation method of the second acrylic polymer is as follows: A surfactant, protective colloid, and deionized water are added to a reaction vessel and mixed thoroughly. Then, the chemical formula CH2=CR is added... 1 The second hydrophilic monomer of COOM has the chemical formula CH2=CHCOOR. 4 The second hydrophobic monomer is added to the reactor, stirred, and nitrogen is purged to remove oxygen. When the water bath temperature is raised to 60-70°C, the second water-soluble initiator solution is added dropwise. After the addition is complete, the reaction is continued at a constant temperature for 2-8 hours. Then the temperature is lowered to stop the reaction. When the temperature drops below 40°C, the material is discharged to obtain the second acrylic polymer. The mass concentration of the first water-soluble initiator solution and the second water-soluble initiator solution is uniformly 5%.

[0007] R 1 The single component is selected from H or a C1-C4 alkyl group, or an amide; M is selected from at least one of H, Li, Na, and K; R 2 The single one is selected from H or methyl; R 3 It is either absent or selected from C1-C4 alkyl groups; R 4 It is selected from one of C2-C22 alkyl groups or one of C2-C22 substituted alkyl groups.

[0008] By employing the above technical solution, the first acrylic polymer and the second acrylic polymer are the main components of the adhesive, together providing excellent dispersibility, high cohesive strength, and excellent flexibility. The first acrylic polymer has high adhesive strength, while the second acrylic polymer has a relatively low glass transition temperature, allowing the prepared adhesive to maintain high adhesive strength while possessing relatively more flexible mechanical properties. Hydrophilic and hydrophobic monomers are used to prepare the first and second acrylic polymers, respectively. The hydrophilic monomer helps improve the affinity and compatibility of the adhesive with the hard carbon anode material, while the hydrophobic monomer helps improve the flexibility of the adhesive. Surfactants: The addition of special surfactants can improve the compatibility and dispersibility of the second acrylic polymer, thereby ultimately improving the bonding strength and flexibility of the hard carbon anode material and the electrode sheet. Protective colloid: The protective colloid helps stabilize the performance of the adhesive and prevents unstable changes during the preparation process. Deionized water: As a solvent, deionized water helps the components to mix thoroughly, forming a uniform adhesive. Water-soluble initiator solution: During the preparation process, the water-soluble initiator solution plays a role in initiating the polymerization reaction, promoting the polymerization of monomers into a polymer. In summary, the sodium-ion battery hard carbon anode two-component acrylate-based aqueous binder of this application achieves excellent dispersion ability, high cohesive strength, and excellent flexibility through the synergistic effect of its components, solving the problem of limited performance in existing binders. Furthermore, this binder is suitable for large-scale production and has high practical value.

[0009] Preferably, the mass ratio of the first hydrophilic monomer, the first hydrophobic monomer, the first water-soluble initiator solution and deionized water is (10-14):(24-30):(10-18):(150-200).

[0010] Preferably, the mass ratio of the second hydrophilic monomer, the second hydrophobic monomer, the second water-soluble initiator solution, the surfactant, the protective gel, and the deionized water is (8-12):(35-40):(9-16):(0.8-1.2):(1-1.5):(150-200).

[0011] Preferably, both the first hydrophilic monomer and the second hydrophilic monomer are selected from at least one of acrylic acid (AA), methacrylic acid (MAA), sodium acrylate (AANa), sodium methacrylate (MAANa), and acrylamide.

[0012] Preferably, the first hydrophobic monomer is selected from at least one of acrylonitrile, methacrylonitrile, and 3-butenonitrile.

[0013] Preferably, the second hydrophobic monomer is selected from soft monomers with a Tg below -10°C, specifically selected from at least one of butyl acrylate, octyl acrylate, isooctyl acrylate, hexyl acrylate, lauryl acrylate, and hydroxyethyl acrylate.

[0014] Preferably, the second hydrophobic monomer is composed of butyl acrylate, isooctyl acrylate and lauryl acrylate in a mass ratio of 5:3:4.

[0015] By adopting the above technical solution, the second hydrophobic monomer is selected from soft monomers with a glass transition temperature (Tg) below -10°C, and is composed of butyl acrylate, isooctyl acrylate, and lauryl acrylate in a mass ratio of 5:3:4. This combination is chosen to achieve the following effects: Lowering the glass transition temperature (Tg): By selecting soft monomers with a Tg below -10°C, the overall glass transition temperature of the adhesive can be lowered, allowing it to maintain good flexibility at low temperatures. This is crucial for the battery's performance in low-temperature environments. Improving flexibility: Butyl acrylate, isooctyl acrylate, and lauryl acrylate all have low glass transition temperatures, and their synergistic effect allows the adhesive to maintain high bonding strength while possessing more flexible mechanical properties. This helps improve the bonding strength and flexibility between the electrode sheet and the hard carbon anode material, thereby improving the electrode's performance and stability. Improving initial coulombic efficiency and reducing impedance: By adding a special surfactant component, the compatibility and dispersibility of the second acrylic polymer were improved, ultimately enhancing the bonding strength and flexibility between the hard carbon anode material and the electrode sheet, and improving initial coulombic efficiency and reducing impedance, thereby improving the performance and stability of the electrode. In summary, by selecting a suitable combination of second hydrophobic monomers (butyl acrylate, isooctyl acrylate, and lauryl acrylate), the binder performance was optimized, improving the performance and stability of the electrode while meeting the needs of large-scale production.

[0016] Preferably, the protective adhesive is one or a mixture of two of sodium polyacrylate, sodium carboxymethyl cellulose, hydroxyethyl cellulose and polyvinyl alcohol, and the initiator is one of ammonium persulfate, potassium persulfate and sodium persulfate.

[0017] Preferably, the surfactant is composed of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30 and octylphenol polyoxyethylene (10) ether in a mass ratio of 3:5:6.

[0018] By adopting the above technical solutions, sodium dodecylbenzenesulfonate, an anionic surfactant, possesses excellent detergency, emulsification, and wetting properties, which can improve the dispersibility of the second acrylic polymer, enabling it to form a uniform coating on the electrode sheet. Polyvinylpyrrolidone K30, a nonionic surfactant, possesses excellent stability, wetting, and adhesion properties, which can improve the compatibility of the second acrylic polymer, allowing it to better bond with the hard carbon anode material. Octylphenol polyoxyethylene (10) ether, a nonionic surfactant, possesses excellent wetting, penetration, and emulsification properties, which can improve the flowability of the second acrylic polymer, enabling it to form a uniform coating on the electrode sheet. Sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30, and octylphenol polyoxyethylene (10) ether, through their complementary and synergistic effects, jointly improve the compatibility and dispersibility of the second acrylic polymer, thereby enhancing the bonding strength and flexibility between the hard carbon anode material and the electrode sheet, improving the initial coulombic efficiency and reducing impedance, thus improving the performance and stability of the electrode.

[0019] Secondly, this application provides a method for preparing a two-component acrylate-based aqueous binder for a sodium-ion battery hard carbon anode, employing the following technical solution:

[0020] As a general technical concept, this application also provides a method for preparing the above-mentioned two-component acrylate aqueous binder for a sodium-ion battery hard carbon anode, comprising the following steps:

[0021] According to the mass fractions, the pH of the first acrylic polymer and the second acrylic polymer are pre-adjusted to 7-9, and then the two are mixed and stirred for 20-30 minutes to obtain a two-component acrylate water-based binder for sodium-ion battery hard carbon negative electrode.

[0022] Thirdly, this application provides an application of a two-component acrylate-based aqueous binder for hard carbon anodes in sodium-ion batteries, employing the following technical solution:

[0023] As a general technical concept, this application also provides the application of the above-mentioned two-component acrylate aqueous binder for sodium-ion battery hard carbon anode in sodium-ion battery hard carbon anode.

[0024] By adopting the above technical solution and using the sodium-ion battery hard carbon anode bicomponent acrylate aqueous binder provided in this application, the bonding strength and flexibility of the hard carbon anode material and the electrode sheet are improved, the first coulombic efficiency is increased and the impedance is reduced, thereby improving the performance and stability of the electrode.

[0025] In summary, this application includes at least one of the following beneficial technical effects:

[0026] 1. By preparing a first acrylic polymer and a second acrylic polymer, the performance of a two-component acrylate-based aqueous binder for hard carbon anodes in sodium-ion batteries was optimized. This optimization is mainly reflected in the binder's dispersion ability, cohesive strength, and flexibility, resulting in better performance in practical applications.

[0027] 2. The introduction of the second hydrophobic monomer results in a relatively low glass transition temperature for the second acrylic polymer, thus ensuring both high adhesive strength and more flexible mechanical properties. This helps improve the affinity and compatibility between the waterborne adhesive and the hard carbon anode material, thereby enhancing the bonding strength and flexibility between the hard carbon anode material and the electrode sheet.

[0028] 3. The preparation method of this application is simple and easy to implement, and suitable for large-scale production. This makes the technical solution of this application highly practical and conducive to promoting the development and application of hard carbon anode materials for sodium-ion batteries.

[0029] 4. The addition of a special surfactant further enhances the compatibility and dispersibility of the second acrylic polymer. This helps to ultimately improve the bonding strength and flexibility between the hard carbon anode material and the electrode sheet, as well as increase the initial coulombic efficiency and reduce impedance, thereby improving the performance and stability of the electrode. Detailed Implementation

[0030] The embodiments of this application will be described in detail below with reference to examples. However, those skilled in the art will understand that the following examples are for illustrative purposes only and should not be considered as limiting the scope of this application. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0031] Example 1

[0032] A two-component acrylate-based aqueous binder for sodium-ion battery hard carbon anodes is prepared from the following raw materials: 40g of a first acrylate polymer and 60g of a second acrylate polymer. The first acrylate polymer is prepared by adding 10g of acrylic acid (AA), 24g of acrylonitrile, and 150g of deionized water to a reaction flask, stirring, and purging with nitrogen to remove oxygen. The mixture is heated to 70°C in a water bath, and then 10g of a 5% ammonium persulfate aqueous solution is added dropwise. The reaction is continued at a constant temperature for 4 hours after the addition is complete. The reaction is then stopped by cooling, and the material is discharged when the temperature drops to 35°C to obtain the first acrylate polymer. The second acrylate polymer is prepared by... The preparation method is as follows: 0.8g of surfactant (the surfactant is composed of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30 and octylphenol polyoxyethylene (10) ether in a mass ratio of 3:5:6), 1g of sodium polyacrylate and 150g of deionized water are added to the reaction vessel and mixed evenly. Then, 8g of acrylic acid (AA) and 35g of butyl acrylate are added to the reaction vessel, stirred and nitrogen is passed through to remove oxygen. When the water bath temperature is raised to 60°C, 9g of 5% ammonium persulfate aqueous solution is added dropwise. After the addition is completed, the reaction is continued at a constant temperature for 2 hours. Then the temperature is lowered to stop the reaction. When the temperature drops to 40°C, the material is discharged to obtain the second acrylic polymer.

[0033] The preparation method of the above-mentioned two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery includes the following steps: adjusting the pH of the first acrylate polymer to 7 and the second acrylate polymer to 7 according to the mass fraction, and then mixing and stirring the two for 20 minutes to obtain the two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery.

[0034] Example 2

[0035] A two-component acrylate-based aqueous binder for sodium-ion battery hard carbon anodes is prepared from the following raw materials: 70g of a first acrylate polymer and 30g of a second acrylate polymer. The first acrylate polymer is prepared by adding 14g of methacrylic acid (MAA), 30g of methacrylonitrile, and 200g of deionized water to a reaction flask, stirring, and purging with nitrogen to remove oxygen. The mixture is heated to 80°C in a water bath, and then 18g of a 5% potassium persulfate aqueous solution is added dropwise. After the addition is complete, the reaction is continued at a constant temperature for 10 hours. The reaction is then stopped by cooling, and the material is discharged when the temperature drops to 40°C to obtain the first acrylate polymer. The second acrylate polymer is prepared by... The method is as follows: 1.2g of surfactant (the surfactant is composed of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30 and octylphenol polyoxyethylene (10) ether in a mass ratio of 3:5:6), 1.5g of sodium carboxymethyl cellulose and 200g of deionized water are added to the reaction vessel and mixed evenly. Then, 12g of methacrylic acid (MAA) and 40g of octyl acrylate are added to the reaction vessel, stirred and nitrogen gas is passed through to remove oxygen. When the water bath temperature is raised to 70°C, 16g of potassium persulfate aqueous solution with a mass concentration of 5% is added dropwise. After the addition is completed, the reaction is continued at a constant temperature for 8 hours. Then the temperature is lowered to stop the reaction. When the temperature drops to 40°C, the material is discharged to obtain the second acrylic polymer.

[0036] The preparation method of the above-mentioned two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery includes the following steps: adjusting the pH of the first acrylate polymer to 9 and the second acrylate polymer to 9 according to the mass parts, and then mixing and stirring the two for 30 minutes to obtain the two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery.

[0037] Example 3

[0038] A two-component acrylate-based aqueous binder for hard carbon anodes in sodium-ion batteries is prepared by means of: 50g of a first acrylate polymer and 50g of a second acrylate polymer. The first acrylate polymer is prepared by adding 13g of sodium acrylate, 27g of 3-butenonitrile, and 180g of deionized water to a reaction flask, stirring, and purging with nitrogen to remove oxygen. The temperature is raised to 75°C in a water bath, and then 15g of a 5% sodium persulfate aqueous solution is added dropwise. After the addition is complete, the reaction is continued at a constant temperature for 6 hours, then the temperature is lowered to stop the reaction. The material is discharged when the temperature drops to 38°C to obtain the first acrylate polymer. The second acrylate polymer is prepared by adding 1g of surfactant (the surfactant is composed of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30, and octyl acrylate) to a reaction vessel. The mixture of 10-hydroxyethyl cellulose and 180g deionized water in a mass ratio of 3:5:6 was prepared. Then, 10g sodium acrylate (AANa) and 37g isooctyl acrylate were added to the reaction vessel. The mixture was stirred and nitrogen gas was introduced to remove oxygen. When the water bath temperature was raised to 65°C, 13g of sodium persulfate aqueous solution with a mass concentration of 5% was added dropwise. After the addition was completed, the reaction was continued at a constant temperature for 5 hours. Then the temperature was lowered to stop the reaction. When the temperature dropped to 37°C, the product was discharged to obtain the second acrylic polymer.

[0039] The preparation method of the above-mentioned two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery includes the following steps: pre-adjusting the pH of the first acrylate polymer to 8 and the second acrylate polymer to 8 according to the mass parts, and then mixing and stirring the two for 25 minutes to obtain the two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery.

[0040] Example 4

[0041] A two-component acrylate-based aqueous binder for sodium-ion battery hard carbon anodes is prepared from the following raw materials: 50g of a first acrylate polymer and 50g of a second acrylate polymer. The first acrylate polymer is prepared by adding 3g of acrylic acid (AA), 7g of sodium methacrylate (MAANa), 4g of acrylamide, 26g of acrylonitrile, and 190g of deionized water to a reaction flask, stirring, and purging with nitrogen to remove oxygen. The mixture is heated to 75°C in a water bath, and then 16g of a 5% (w / w) aqueous solution of ammonium persulfate, potassium persulfate, and sodium persulfate is added dropwise. The reaction is continued at a constant temperature for 7 hours after the addition is complete, then the temperature is lowered to stop the reaction. The material is discharged when the temperature drops to 36°C to obtain the first acrylate polymer. The second acrylate polymer... The preparation method is as follows: 1.1g of surfactant (the surfactant is composed of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30 and octylphenol polyoxyethylene (10) ether in a mass ratio of 3:5:6), 1.3g of polyvinyl alcohol and 180g of deionized water are added to the reaction vessel and mixed evenly. Then, 4g of acrylic acid (AA), 5% sodium acrylate (AANa), 4% sodium methacrylate (MAANa) and 36g of hexyl acrylate are added to the reaction vessel. The mixture is stirred and nitrogen is passed through to remove oxygen. When the water bath temperature is raised to 65°C, 12g of 5% ammonium persulfate aqueous solution is added dropwise. After the addition is completed, the reaction is continued at a constant temperature for 5 hours. Then the temperature is lowered to stop the reaction. When the temperature drops to 38°C, the material is discharged to obtain the second acrylic polymer.

[0042] The preparation method of the above-mentioned two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery includes the following steps: adjusting the pH of the first acrylate polymer to 8.3 and the pH of the second acrylate polymer to 8.3 according to the mass parts, and then mixing and stirring the two for 25 minutes to obtain the two-component acrylate aqueous binder for hard carbon anode of sodium-ion battery.

[0043] Example 5

[0044] A two-component acrylate-based aqueous binder for sodium-ion battery hard carbon anodes is prepared by means of: 50g of a first acrylate polymer and 50g of a second acrylate polymer. The first acrylate polymer is prepared by adding 4g of acrylic acid (AA), 3g of methacrylic acid (MAA), 5g of sodium methacrylate (MAANa), 25g of 3-butenonitrile, and 180g of deionized water to a reaction flask, stirring, and purging with nitrogen to remove oxygen. The temperature is raised to 75°C in a water bath, and then 14g of a 5% ammonium persulfate aqueous solution is added dropwise. After the addition is complete, the reaction is continued at a constant temperature for 6 hours, then the temperature is lowered to stop the reaction. The material is discharged when the temperature drops to 37°C to obtain the first acrylate polymer. The second acrylate polymer is prepared by adding 1g of surfactant (the surfactant being sodium dodecylbenzenesulfonate and polyvinylpyrrolidone K3) to a reaction vessel. 0 and octylphenol polyoxyethylene (10) ether were composed of 3:5:6 by mass ratio, 1.2g sodium carboxymethyl cellulose and 180g deionized water were mixed evenly, and then 9g acrylamide and 37g hydroxyethyl acrylate were added to the reaction vessel. The mixture was stirred and nitrogen gas was passed through to remove oxygen. When the water bath temperature was raised to 65°C, 12g sodium persulfate aqueous solution with a mass concentration of 5% was added dropwise. After the addition was completed, the reaction was continued at a constant temperature for 5 hours. Then the temperature was lowered to stop the reaction. When the temperature dropped to 38°C, the material was discharged to obtain the second acrylic polymer.

[0045] The preparation method of the above-mentioned two-component acrylate-based aqueous binder for hard carbon anode of sodium-ion battery includes the following steps: adjusting the pH of the first acrylate polymer to 7.3 and the pH of the second acrylate polymer to 7.3 according to the mass fractions, and then mixing and stirring the two for 25 minutes to obtain the two-component acrylate-based aqueous binder for hard carbon anode of sodium-ion battery.

[0046] Example 6

[0047] Same as Example 5, except that an equal amount of a second hydrophobic monomer (composed of butyl acrylate, isooctyl acrylate and lauryl acrylate in a mass ratio of 5:3:4) is used instead of hydroxyethyl acrylate.

[0048] Comparative Example 1

[0049] Same as Example 6, except that an equal amount of butyl acrylate is used instead of the second hydrophobic monomer.

[0050] Comparative Example 2

[0051] Same as Example 6, except that an equal amount of isooctyl acrylate is used instead of the second hydrophobic monomer.

[0052] Comparative Example 3

[0053] Same as Example 6, except that an equal amount of lauryl acrylate is used instead of the second hydrophobic monomer.

[0054] Comparative Example 4

[0055] Same as Example 6, except that the surfactant is sodium dodecylbenzenesulfonate.

[0056] Comparative Example 5

[0057] Same as Example 6, except that the surfactant is polyvinylpyrrolidone K30.

[0058] Comparative Example 6

[0059] Same as in Example 6, except that the surfactant is octylphenol polyoxyethylene (10) ether.

[0060] Performance testing

[0061] Test methods

[0062] The preparation method of hard carbon anode slurry and electrode sheet is as follows: dry weight ratio of hard carbon formulation slurry, two-component acrylic water-based binder: SP: hard carbon anode material (425mAh / g) = 3.5:1:95.5.

[0063] In the slurry preparation process, the water addition was calculated based on a solid content of 45% for the negative electrode slurry before viscosity adjustment. 3.5 parts of the sodium-ion battery hard carbon negative electrode bicomponent acrylate aqueous binder prepared in Examples 1-6 and Comparative Examples 1-6 were mixed with 50% water and dispersed at 300 rpm for 15 minutes. Then, 1 part of SP conductive carbon black was added, and the mixture was stirred at 150 rpm for 10 minutes, followed by high-speed stirring at 800 rpm for 120 minutes. The stirring speed was then reduced to 300 rpm, and 50% of the hard carbon negative electrode material was added and dispersed for 10 minutes. The remaining 50% of the hard carbon negative electrode material and the remaining 50% of the water were then added and dispersed for 10 minutes, followed by high-speed stirring at 800 rpm for 120 minutes. After high-speed stirring, the viscosity (at 25°C) was adjusted to between 3000 and 4000 mPa·s, and the mixture was filtered through a 150-mesh filter to obtain the negative electrode slurry.

[0064] In the preparation process of the CMC+SRS comparative slurry, the water addition was calculated based on a solid content of 45% in the negative electrode slurry before viscosity adjustment. 1.75 parts of CMC and 50% of water were mixed and dispersed at 300 rpm for 15 minutes. Then, 1 part of SP conductive carbon black was added, and the mixture was stirred at 150 rpm for 10 minutes, followed by high-speed stirring at 800 rpm for 120 minutes. The stirring speed was then reduced to 300 rpm, and 50% of the hard carbon negative electrode material was added and dispersed for 10 minutes. The remaining 50% of the hard carbon negative electrode material and the remaining 50% of the water were then added and dispersed for 10 minutes, followed by high-speed stirring at 800 rpm for 120 minutes. After high-speed stirring, the viscosity (at 25℃) was adjusted to between 3000 and 4000 mPa·s. Then, 1.75 parts of SBR were added, and the mixture was dispersed at 500 rpm for 30 minutes. Finally, the mixture was filtered through a 150-mesh filter to obtain the CMC+SRS comparative negative electrode slurry.

[0065] In the electrode preparation process, copper foil is placed on a coating machine, the scraper scale of the wet film preparation device is adjusted, the filtered slurry is poured evenly, and the film is placed in a 100℃ environment for forced-air drying until dry. The film is then cut into 12.5cm × 5cm pieces with a single-sided areal density of 100-110 g / m³. 2 The electrode film.

[0066] Method for testing the solid content of slurry: Weigh the container made of tin foil using an electronic balance as m1, tare the contents, and weigh the slurry as m2 (1.0000g≤m2≤1.1000g). Place the container containing the slurry in a 150℃ forced-air oven and dry for 30 minutes. Remove the container and weigh it as m3. The solid content of the slurry = (m3-m1) / m2*100%.

[0067] Electrode peel strength test method: Place the cut electrode sheets in a 35% RH constant temperature chamber for 30 minutes. With the coated side facing outwards and the copper foil side facing inwards, bond two electrode sheets together and feed them into an electric roller press to compress the electrode sheets until the compaction density is 0.95 g / cm³. 3 After rolling, let it sit for 30 minutes. During this time, select five 12.5cm×5cm stainless steel plates, apply double-sided tape of the corresponding size to the stainless steel plates, and then attach the electrode sheet to the double-sided tape with the coating facing down. Then, attach a 2.5cm wide masking tape to the copper foil. Roll the electrode sheet steel plate back and forth once with a certain pressure (1kg) using an electric rolling roller. Then, use an electronic peeling machine to test the adhesion of the electrode sheet. The same method is used, but the electrode sheet is attached to the double-sided tape with the coating facing up, and the cohesion of the electrode sheet can be tested.

[0068] The softness was tested using an IMT-RRD01*1 softness tester. The smaller the value, the softer the electrode sheet is.

[0069] Electrode resistivity test method: Use an electrode resistivity meter of model BER2500 to test the electrode resistivity.

[0070] The assembly sequence of the button cell is from bottom to top: negative electrode shell - spring contact - gasket - lithium sheet - electrolyte - separator - electrolyte - electrode - positive electrode shell; the initial coulomb efficiency and impedance tests are as follows: initial efficiency test 0.1C, 0.005-1.5V charge and discharge; impedance scan from 100kHz to 0.1Hz.

[0071] Table 1 Performance Tests

[0072]

[0073] Analyzing the data in Table 1, we can see that:

[0074] 1) The two-component acrylate waterborne adhesives prepared in Examples 1-6 have excellent dispersibility, high cohesive strength and excellent flexibility, which solves the problem of the single performance of existing adhesives. The two-component acrylate waterborne adhesives improve the bonding strength and softness between hard carbon anode materials and electrode sheets, and improve the first coulombic efficiency and reduce impedance, thereby improving the performance and stability of the electrode.

[0075] 2) The performance comparison analysis of the two-component acrylate waterborne adhesives prepared in Example 6 and Comparative Examples 1-3 shows that by using the second hydrophobic monomer composed of butyl acrylate, isooctyl acrylate and lauryl acrylate in a mass ratio of 5:3:4, and utilizing their synergistic effect, the two-component acrylate waterborne adhesive can maintain high adhesion while possessing more flexible mechanical properties. This optimizes the performance of the two-component acrylate waterborne adhesive, improves the performance and stability of the electrode, and meets the needs of large-scale production.

[0076] 3) The performance comparison analysis of the two-component acrylate waterborne adhesives prepared in Example 6 and Comparative Examples 4-6 shows that the surfactant is composed of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30 and octylphenol polyoxyethylene (10) ether in a mass ratio of 3:5:6. Through their complementary properties and synergistic effects, they jointly improve the compatibility and dispersibility of the second acrylate polymer, thereby improving the bonding strength and softness between the hard carbon anode material and the electrode sheet, and improving the first coulombic efficiency and reducing impedance, thus improving the performance and stability of the electrode.

[0077] The above embodiments are only used to explain the technical solutions of this application and are not intended to limit it. Although the above embodiments have provided specific descriptions of this application, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation methods of this application. Any modifications and equivalent substitutions that do not depart from the spirit and scope of this application should be covered within the protection scope of this application.

Claims

1. A two-component acrylate-based aqueous binder for hard carbon anodes in sodium-ion batteries, characterized in that, Based on a total mass fraction of 100, the raw materials include: 40-70 parts of a first acrylic polymer and 30-60 parts of a second acrylic polymer. The first acrylic polymer is prepared by: using a polymer with the chemical formula CH2=CR... 1 COOM's first hydrophilic monomer has the chemical formula R. 2 CH=CHR 3 The first hydrophobic monomer of CN and deionized water are added to a reaction flask, stirred, and nitrogen is purged to remove oxygen. The water bath temperature is raised to 70-80℃, and then the first water-soluble initiator solution is added dropwise. After the addition is complete, the reaction is continued at a constant temperature for 4-10 hours. The reaction is then stopped by cooling, and the product is discharged when the temperature drops below 40℃ to obtain the first acrylic polymer. The preparation method of the second acrylic polymer is as follows: A surfactant, protective colloid, and deionized water are added to a reaction vessel and mixed thoroughly. Then, the chemical formula CH2=CR is added... 1 The second hydrophilic monomer of COOM has the chemical formula CH2=CHCOOR. 4 The second hydrophobic monomer is added to the reactor, stirred, and nitrogen is purged to remove oxygen. When the water bath temperature is raised to 60-70°C, the second water-soluble initiator solution is added dropwise. After the addition is complete, the reaction is continued at a constant temperature for 2-8 hours. Then the temperature is lowered to stop the reaction. When the temperature drops below 40°C, the material is discharged to obtain the second acrylic polymer. The mass concentration of both the first and second water-soluble initiator solutions is 5%. R 1 The single component is selected from H or C1-C4 alkyl; M is selected from at least one of H, Li, Na, and K; R 2 The single one is selected from H or methyl; R 3 It is either absent or selected from C1-C4 alkyl groups; R 4 The surfactant is selected from one of C2-C22 alkyl groups or one of C2-C22 substituted alkyl groups, wherein the substitution is hydroxyl substitution; the surfactant is composed of sodium dodecylbenzenesulfonate, polyvinylpyrrolidone K30 and octylphenol polyoxyethylene (10) ether in a mass ratio of 3:5:

6.

2. The aqueous acrylate binder for a hard carbon anode in a sodium-ion battery according to claim 1, characterized in that, The mass ratio of the first hydrophilic monomer, the first hydrophobic monomer, the first water-soluble initiator solution and deionized water is (10-14):(24-30):(10-18):(150-200).

3. The aqueous acrylate binder for a hard carbon anode in a sodium-ion battery according to claim 1, characterized in that, The mass ratio of the second hydrophilic monomer, the second hydrophobic monomer, the second water-soluble initiator solution, the surfactant, the protective colloid, and the deionized water is (8-12):(35-40):(9-16):(0.8-1.2):(1-1.5):(150-200).

4. The aqueous acrylate binder for a hard carbon anode in a sodium-ion battery according to claim 1, characterized in that, Both the first hydrophilic monomer and the second hydrophilic monomer are selected from at least one of acrylic acid, methacrylic acid, sodium acrylate and sodium methacrylate.

5. The aqueous acrylate binder for a hard carbon anode in a sodium-ion battery according to claim 1, characterized in that, The first hydrophobic monomer is selected from at least one of acrylonitrile, methacrylonitrile and 3-butenonitrile.

6. The aqueous acrylate binder for a hard carbon anode in a sodium-ion battery according to claim 1, characterized in that, The second hydrophobic monomer is selected from soft monomers with a Tg below -10°C, specifically from at least one of butyl acrylate, octyl acrylate, isooctyl acrylate, hexyl acrylate, lauryl acrylate, and hydroxyethyl acrylate.

7. The aqueous acrylate binder for a hard carbon anode in a sodium-ion battery according to claim 1, characterized in that, The initiator is one of ammonium persulfate, potassium persulfate, and sodium persulfate.

8. A method for preparing a two-component acrylate-based aqueous binder for a sodium-ion battery hard carbon anode as described in any one of claims 1-7, characterized in that, Includes the following steps: According to the mass fractions, the pH of the first acrylic polymer and the second acrylic polymer are pre-adjusted to 7-9, and then the two are mixed and stirred for 20-30 minutes to obtain a two-component acrylate water-based binder for sodium-ion battery hard carbon negative electrode.

9. The application of a two-component acrylate aqueous binder for a sodium-ion battery hard carbon anode as described in any one of claims 1-7 in the hard carbon anode of a sodium-ion battery.

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