Water-based htpb binder for lithium battery cathode and preparation method thereof

Abstract

The present application belongs to the technical field of lithium battery, and particularly relates to a water-based HTPB binder for lithium battery positive electrode and a preparation method thereof. The present application provides a high-molecular polymer composite water-based binder with a core-shell structure based on HTPB water-based technology, which is mainly prepared by acrylation of HTPB with isocyanate propyl, and then emulsion polymerization with sodium methacrylate solution, acrylonitrile, acrylamide and acrylate monomer. The product has no VOC residue, and is an environmentally friendly, non-toxic and pure green water-based binder. Compared with the existing water-based positive electrode binder, the water-based HTPB binder provided by the present application has a toughness increased by more than 2 times, and the peeling force is also increased by more than 1 time. The battery prepared by the water-based HTPB binder provided by the present application has a capacity retention rate of more than 80% after 6000 cycles.

Description

Technical Field

[0001] This invention belongs to the field of lithium battery technology, specifically relating to a water-based HTPB binder for the positive electrode of a lithium battery and its preparation method. Background Technology

[0002] Binders play a crucial role in the manufacturing process of lithium-ion batteries, profoundly impacting their overall performance. In the manufacturing process of lithium-ion battery positive electrode sheets, organic solvent-based polyvinylidene fluoride (PVDF) is widely used as a binder. For example, Chinese patent CN114566648B discloses a PVDF conductive binder for lithium-ion battery positive electrodes, which effectively reduces the swelling of the positive electrode system in the electrolyte, ensures stable adhesion of active materials in the positive electrode current collector, and exhibits good resistance to polar organic solvents. However, the fluorine element in PVDF readily reacts chemically with materials such as lithium-intercalated graphite, which to some extent limits further improvements in lithium-ion battery performance. Therefore, developing new binder systems to optimize the manufacturing process of lithium-ion battery positive electrodes and improve their performance has become an urgent need for the industry.

[0003] In recent years, aqueous binders have gradually become a research hotspot and development direction in the field of lithium-ion battery binders due to their multiple advantages, such as no VOC release, environmental friendliness, low cost, non-flammability, and high safety. Although significant progress has been made in the research of aqueous binders in the field of anode materials, and their commercial application in graphite anodes has been achieved, the application of aqueous binders in the cathode of lithium-ion batteries has not yet been commercialized.

[0004] Currently, water-based binders for lithium-ion batteries generally suffer from insufficient flexibility and excessive rigidity, severely restricting their application in new production processes. Taking lithium iron phosphate anode material as an example, lithium iron phosphate itself has relatively low conductivity, requiring surface nano-coating technology to improve it. However, the modification process often leads to the material becoming porous, thus reducing compaction density. Therefore, developing a novel binder that can improve the compaction density of lithium battery cathode materials while simultaneously meeting the requirements for electrode flexibility and the surface conductivity of active materials is of great significance for promoting the development of the lithium-ion battery industry. Summary of the Invention

[0005] To obtain a water-based binder for lithium-ion battery cathodes with high flexibility, this invention provides an aqueous technology for HTPB (hydroxyl-terminated polybutadiene), which can prepare novel polymer composite water-based binders with core-shell structures.

[0006] The first aspect of this invention provides an aqueous HTPB binder for lithium battery cathodes, the raw materials of which include HTPB, propylene isocyanate, acrylic monomer, acrylonitrile, acrylamide, acrylate monomers, catalyst, pH adjuster, initiator, surfactant and HTPB solvent.

[0007] As an implementable example, the mass ratio of HTPB, propylene isocyanate, acrylic monomer, acrylonitrile, acrylamide, and acrylate monomer is (10-30):(2-15):(15-35):(10-35):(10-20):(5-10).

[0008] As an implementable example, the HTPB includes one or more of type I HTPB, type II HTPB, type III HTPB, and type IV HTPB.

[0009] As an feasible example, the HTPB has a hydroxyl value of 0.4-0.80 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 2000-5000.

[0010] Furthermore, the type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600; the type II HTPB has a hydroxyl value of 0.54-0.64 mmol / g, a viscosity of ≤8.5 Pa•s at 40 ℃, and a number-average molecular weight of 3300-4100; the type III HTPB has a hydroxyl value of 0.65-0.70 mmol / g, a viscosity of ≤4.0 Pa•s at 40 ℃, and a number-average molecular weight of 3000-3600; and the type IV HTPB has a hydroxyl value of 0.71-0.80 mmol / g, a viscosity of ≤3.5 Pa•s at 40 ℃, and a number-average molecular weight of 2700-3300.

[0011] This invention primarily uses low-viscosity HTPB as the main raw material for preparing water-based binders. Low-viscosity HTPB can achieve the required slurry viscosity with less solvent, thereby reducing solvent usage, lowering costs and reducing environmental pollution. In addition, low-viscosity HTPB has better fluidity, making it easier to mix uniformly with electrode materials and form a stable slurry. Most importantly, the molecular chain length of low-viscosity HTPB is moderate, making it easier to chemically modify it with propylene isocyanate, acrylic acid monomers, acrylic acid monomers, acrylamide, and acrylate monomers. The modified polymerization product has a core-shell structure, thereby optimizing the bonding and mechanical properties of the water-based binder.

[0012] As an implementable example, the acrylic monomers include acrylic acid and / or methacrylic acid.

[0013] As an implementable example, the acrylate monomers include one or more of butyl acrylate, isooctyl acrylate, and vinyl acetate.

[0014] As an implementable example, the catalyst comprises one of dibutyltin dilaurate, dioctyltin dilaurate, dimethyltin dilaurate, bismuth octanoate, zinc octanoate, and triethylenediamine.

[0015] Furthermore, the catalyst is dibutyltin dilaurate.

[0016] As an example of an implementation, the pH adjuster may include sodium hydroxide or potassium hydroxide.

[0017] Furthermore, the pH adjuster is sodium hydroxide.

[0018] In this invention, potassium hydroxide is selected as a pH adjuster, which can react with acrylic monomers through an acid-base reaction to prepare sodium acrylate, thereby modifying HTPB and further improving the mechanical and adhesive properties of waterborne HTPB adhesives.

[0019] As an implementable example, the initiator includes one of the following: ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxide, dicyclohexyl peroxide, tert-butyl peroxide, cumene hydroperoxide, tert-butyl hydroperoxide, and an organic amine catalyst.

[0020] As an example of implementation, the surfactant includes one of anionic surfactants, cationic surfactants, nonionic surfactants, and amphoteric surfactants.

[0021] Furthermore, the surfactant is a nonionic surfactant.

[0022] Furthermore, the nonionic surfactant includes polyoxyethylene nonylphenol ether-14.

[0023] As an example of implementation, the HTPB solvent includes one of dichloromethane, ethyl acetate, methanol, and acetonitrile.

[0024] Furthermore, the HTPB solvent includes dichloromethane.

[0025] A second aspect of this invention provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, comprising:

[0026] S1. Mix HTPB, propylene isocyanate, catalyst and HTPB solvent, heat to 30-40 ℃, and then stir for 3-5 h to obtain propylene-based HTPB solution. Cool to 20-30 ℃ for later use.

[0027] The pH adjuster and acrylic monomer were mixed and stirred to obtain an acrylate solution, which was then cooled to 20-30 ℃ for later use.

[0028] S2. Add surfactant, acrylate solution, acrylonitrile, acrylamide, and acrylate monomer to the propylene-based HTPB solution, stir at 300-500 rpm for 30-60 min, and then remove the HTPB solvent by vacuum to obtain the reaction emulsion.

[0029] S3. Inert gas is introduced into the reaction emulsion, the stirring speed is reduced to 100-200 rpm, then the temperature is raised to 40-50 ℃, the initiator is added dropwise, and the mixture is stirred at 50-90 ℃ for 6-12 h. After cooling to 20-30 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for lithium battery positive electrode.

[0030] In the preparation of the reaction emulsion, this invention eliminates the need for additional organic solvents. Instead, it utilizes the water / oil biphase solubility of acrylonitrile monomers, which exhibits good bidirectional solubility for both oily and polar monomers. It combines the dual functions of reactant and solvent, forming a stable emulsion in the aqueous phase for aqueous emulsion polymerization. This also further reduces production costs and VOC emissions.

[0031] The water-based HTPB binder for lithium battery cathodes provided by this invention has a viscosity of 9.8-12.1 Pa•s, a pH value of 6.0-8.0, and a solid content of 8.0 wt% at 40 ℃. The product has no VOC residue and is an environmentally friendly, non-toxic, and purely green water-based binder.

[0032] Viscosity control of waterborne HTPB adhesives is crucial for both production and application. At the same solid content, too low a viscosity results in a small molecular weight, leading to poor adhesion; conversely, too high a viscosity can overload production equipment, potentially causing damage. Therefore, it is essential to maintain the viscosity of waterborne HTPB adhesives within a reasonable range.

[0033] In this invention, by strictly controlling the reaction temperature and taking a cooling step after the reactants reach a certain temperature, the degree of polymerization of the product is controlled, so that the viscosity of the water-based binder is in the range of 9.0-20.0 Pa•s under the conditions of 40 ℃, 10.0 wt% solid content and pH value of 6.0-8.0.

[0034] Beneficial effects

[0035] (i) The novel water-based HTPB binder provided by this invention adopts water-based technology, which avoids the environmental pollution problems of traditional organic solvent-based binders (such as PVDF system). It is an environmentally friendly, non-toxic, and pure green binder, and is especially suitable for use in lithium-ion battery cathode materials.

[0036] (ii) The present invention mainly uses a core-shell structure design, in which the hydrophobic core is HTPB and the hydrophilic shell is a 2-polyacrylic acid polymer chain, which significantly enhances the flexibility of the prepared waterborne HTPB adhesive, increases the elongation at break, and significantly improves the peel force (more than 1 times higher than existing waterborne adhesives), so as to better adapt to the volume change of the electrode material during the charging and discharging process and prevent the electrode from cracking or falling off.

[0037] (iii) Batteries prepared using the aqueous HTPB binder provided by the present invention retain more than 85% of their capacity after 6,000 cycles, demonstrating excellent cycle stability and are especially suitable for high energy density batteries.

[0038] (iv) The water-based HTPB binder provided by the present invention can still maintain good discharge performance in a low temperature environment of -20℃. The low temperature discharge capacity and median voltage of the battery are better than those of traditional binders, and it is suitable for use in a wide temperature range.

[0039] (v) In the process of preparing the reaction emulsion, the present invention does not require additional organic solvents, but utilizes the water / oil two-phase solubility of acrylonitrile monomers to effectively reduce VOC emissions in production costs, while not affecting the bonding performance and electrical properties of water-based adhesives. Attached Figure Description

[0040] Figure 1 This is a schematic diagram of the chemical reactions involved in the preparation of water-based HTPB adhesives.

[0041] Figure 2 This is a schematic diagram of the core-shell structure model of an aqueous HTPB binder, where 1-HTPB is a hydrophobic core and 2-polyacrylic acid polymer chains form a hydrophilic shell.

[0042] Figure 3 The image shows a SEM image of the waterborne HTPB adhesive prepared in Example 7, with a scale bar of 1 μm.

[0043] Figure 4 This is a schematic diagram illustrating the battery cycle performance of the aqueous HTPB binder prepared in Example 7 and Comparative Example 1 when applied in a battery. Test conditions: The battery was charged to 4.35 V at a 1C rate and then kept at a constant voltage of 4.35 V; then the battery was discharged at a 1C rate with a cutoff voltage of 3.0 V, completing one cycle.

[0044] Figure 5 This is a schematic diagram illustrating the low-temperature discharge performance of batteries using the aqueous HTPB binders prepared in Example 7 and Comparative Example 1. Test conditions: 1C rate discharge to 2.5 V at -20 °C. Detailed Implementation

[0045] Example 1

[0046] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 20 parts type I HTPB, 5 parts propylene isocyanate, 30 parts methacrylic acid, 20 parts acrylonitrile, 20 parts acrylamide, 5 parts butyl acrylate, 0.2 parts dibutyltin dilaurate, 9 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.4 parts polyoxyethylene nonylphenol ether-14, and 40 parts dried dichloromethane.

[0047] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0048] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0049] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0050] S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0051] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0052] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0053] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0054] The water-based adhesive prepared in this example has a pH of 7.0, a viscosity of 10.3 Pa•s, and an appearance of white latex at 40 ℃ and 8.0 wt% solid content.

[0055] Example 2

[0056] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 20 parts type II HTPB, 5 parts propylene isocyanate, 30 parts methacrylic acid, 20 parts acrylonitrile, 20 parts acrylamide, 5 parts butyl acrylate, 0.2 parts dibutyltin dilaurate, 9 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.4 parts polyoxyethylene nonylphenol ether-14, and 40 parts dried dichloromethane.

[0057] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0058] The type II HTPB has a hydroxyl value of 0.54-0.64 mmol / g, a viscosity of ≤8.5 Pa•s at 40 ℃, and a number-average molecular weight of 3300-4100. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0059] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0060] S1. Mix type II HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0061] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0062] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0063] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0064] The water-based adhesive prepared in this example has a pH of 7.1, a viscosity of 10.1 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0065] Example 3

[0066] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 20 parts type III HTPB, 5 parts propylene isocyanate, 30 parts methacrylic acid, 20 parts acrylonitrile, 20 parts acrylamide, 5 parts butyl acrylate, 0.2 parts dibutyltin dilaurate, 9 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.4 parts polyoxyethylene nonylphenol ether-14, and 40 parts dried dichloromethane.

[0067] The type III HTPB has a hydroxyl value of 0.65-0.70 mmol / g, a viscosity of ≤4.0 Pa•s at 40 ℃, and a number-average molecular weight of 3000-3600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0068] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0069] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0070] S1. Mix type III HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0071] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0072] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0073] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0074] The aqueous adhesive prepared in this example has a pH of 7.1, a viscosity of 9.9 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0075] Example 4

[0076] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 20 parts type IV HTPB, 5 parts propylene isocyanate, 30 parts methacrylic acid, 20 parts acrylonitrile, 20 parts acrylamide, 5 parts butyl acrylate, 0.2 parts dibutyltin dilaurate, 9 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.4 parts polyoxyethylene nonylphenol ether-14, and 40 parts dried dichloromethane.

[0077] The type IV HTPB has a hydroxyl value of 0.71-0.80 mmol / g, a viscosity of ≤3.5 Pa•s at 40 ℃, and a number-average molecular weight of 2700-3300. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0078] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0079] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0080] S1. Mix type IV HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0081] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0082] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0083] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0084] The water-based adhesive prepared in this example has a pH of 7.0, a viscosity of 9.8 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0085] Example 5

[0086] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 10 parts type I HTPB, 2.5 parts propylene isocyanate, 30 parts methacrylic acid, 32.5 parts acrylonitrile, 20 parts acrylamide, 5 parts butyl acrylate, 0.1 parts dibutyltin dilaurate, 9.8 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.2 parts polyoxyethylene nonylphenol ether-14, and 20 parts dried dichloromethane.

[0087] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0088] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0089] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0090] S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0091] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0092] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0093] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0094] The aqueous adhesive prepared in this example has a pH of 7.1, a viscosity of 11.2 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0095] Example 6

[0096] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 15 parts type I HTPB, 3.75 parts propylene isocyanate, 30 parts methacrylic acid, 26.5 parts acrylonitrile, 20 parts acrylamide, 5 parts butyl acrylate, 0.15 parts dibutyltin dilaurate, 9 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.3 parts polyoxyethylene nonylphenol ether-14, and 30 parts dried dichloromethane.

[0097] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0098] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0099] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0100] S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0101] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0102] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0103] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0104] The aqueous adhesive prepared in this example has a pH of 7.1, a viscosity of 11.2 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0105] Example 7

[0106] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 25 parts type I HTPB, 6.25 parts propylene isocyanate, 23.75 parts methacrylic acid, 20 parts acrylonitrile, 20 parts acrylamide, 5 parts butyl acrylate, 0.25 parts dibutyltin dilaurate, 7.2 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.5 parts polyoxyethylene nonylphenol ether-14, and 50 parts dried dichloromethane.

[0107] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0108] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0109] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0110] S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0111] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0112] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0113] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0114] The water-based adhesive prepared in this example has a pH of 7.0, a viscosity of 10.6 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0115] The SEM image of the water-based HTPB adhesive prepared in this example is shown below. Figure 3 As shown.

[0116] Example 8

[0117] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 30 parts type I HTPB, 7.5 parts propylene isocyanate, 20 parts methacrylic acid, 20 parts acrylonitrile, 17.5 parts acrylamide, 5 parts butyl acrylate, 0.3 parts dibutyltin dilaurate, 6 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.6 parts polyoxyethylene nonylphenol ether-14, and 60 parts dried dichloromethane.

[0118] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0119] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0120] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0121] S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0122] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0123] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0124] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0125] The water-based adhesive prepared in this example has a pH of 7.1, a viscosity of 12.1 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0126] Example 9

[0127] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 20 parts type I HTPB, 5 parts propylene isocyanate, 35 parts methacrylic acid, 20 parts acrylonitrile, 15 parts acrylamide, 5 parts butyl acrylate, 0.2 parts dibutyltin dilaurate, 7 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.4 parts polyoxyethylene nonylphenol ether-14, and 40 parts dried dichloromethane.

[0128] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0129] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0130] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0131] S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0132] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0133] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0134] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0135] The water-based adhesive prepared in this example has a pH of 7.0, a viscosity of 10.6 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0136] Example 10

[0137] The first aspect of this example provides an aqueous HTPB binder for the positive electrode of a lithium battery. The raw materials for its preparation, by mass parts, are: 20 parts type I HTPB, 5 parts propylene isocyanate, 35 parts methacrylic acid, 20 parts acrylonitrile, 10 parts acrylamide, 10 parts butyl acrylate, 0.2 parts dibutyltin dilaurate, 7 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, 0.4 parts polyoxyethylene nonylphenol ether-14, and 40 parts dried dichloromethane.

[0138] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. It was purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0139] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0140] The second aspect of this example provides a method for preparing a water-based HTPB binder for the positive electrode of a lithium battery, specifically as follows:

[0141] S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain propylene-based HTPB solution. Cool to 25°C for later use.

[0142] Sodium hydroxide aqueous solution and methacrylic acid were mixed and stirred to obtain sodium methacrylate solution, which was then cooled to 25°C for later use.

[0143] S2. Polyoxyethylene nonylphenol ether-14, sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate are added sequentially to the propylene-based HTPB solution. The mixture is stirred at 300 rpm for 30 min, and then dichloromethane is removed by vacuum to obtain the reaction emulsion.

[0144] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 ℃. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80 ℃ for 9 h. After cooling to 25 ℃, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium battery.

[0145] The aqueous adhesive prepared in this example has a pH of 7.1, a viscosity of 11.5 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 10.0 wt%.

[0146] The schematic diagrams of the chemical reactions involved in the preparation of the water-based HTPB adhesives in Examples 1-10 are shown below. Figure 1 As shown.

[0147] Schematic diagrams of the core-shell structure models of waterborne HTPB binders in Examples 1-10 are shown below. Figure 2 As shown, 1-HTPB hydrophobic core, 2-polyacrylic acid polymer chain hydrophilic shell.

[0148] Comparative Example 1

[0149] The first aspect of this example provides an aqueous binder for the positive electrode of a lithium battery, the raw materials for which are prepared by mass parts are: 45 parts methacrylic acid, 20 parts acrylonitrile, 15 parts acrylamide, 20 parts butyl acrylate, 5 parts sodium hydroxide aqueous solution with a mass concentration of 46.4 wt%, 0.1 parts ammonium persulfate aqueous solution with a mass concentration of 1 wt%, and 0.4 parts polyoxyethylene nonylphenol ether-14.

[0150] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0151] The second aspect of this example provides a method for preparing an aqueous binder for the positive electrode of a lithium battery, specifically as follows:

[0152] S1. Mix and stir sodium hydroxide aqueous solution, deionized water and methacrylic acid to obtain sodium acrylate solution, cool to 25 ℃ and set aside.

[0153] S2. Mix acrylonitrile, acrylamide, butyl acrylate and polyoxyethylene nonylphenol ether-14 and stir at 300 rpm for 30 min to obtain a reaction emulsion.

[0154] S3. Nitrogen gas is introduced into the reaction emulsion, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 60°C. An aqueous solution of ammonium persulfate is added dropwise, and the mixture is stirred at 80°C for 9 hours. After cooling to 25°C, the binder is removed, diluted with water, and filtered to obtain the water-based HTPB binder for the positive electrode of lithium batteries.

[0155] The aqueous adhesive prepared in this example has a pH of 7.0, a viscosity of 6.1 Pa•s, and an appearance of white latex at 40 ℃ and a solid content of 15.0 wt%.

[0156] Performance testing

[0157] I. Elongation at break test of adhesive film

[0158] The adhesive films corresponding to Examples 1-10 and Comparative Example 1 were prepared according to ASTM standard D638. The elongation at break of the adhesive films was tested, with five samples for each selected strain rate (the experimental results are the average of five groups). The experiments were conducted under constant temperature and humidity conditions: 25 ℃, 40% RH (humidity); the test results are detailed in Table 1. The standard procedure for preparing the adhesive film samples was as follows: 100g of adhesive sample was weighed into a polytetrafluoroethylene mold (length × width × height: 250 × 40 × 10 mm), and the mold containing the sample was placed on a horizontal table. After the adhesive sample in the mold had leveled, the mold containing the adhesive sample was placed in an oven with a horizontal tray and dried at 60 ℃ to obtain the adhesive film. Defect-free adhesive films were selected and cut to specifications according to ASTM standards for testing. These films were then stored under constant temperature and humidity for testing.

[0159] Table 1

[0160]

[0161] As can be seen from the experimental results in Table 1, the water-based HTPB adhesive prepared by this invention has a film elongation at break of more than 100%, and has high flexibility.

[0162] II. 180° Peel Force Test

[0163] Using the binders from Examples 1-10 and Comparative Example 1, positive electrode sheets were prepared. The specific methods and results are as follows: 93 parts of lithium iron phosphate compound (Hunan Yuneng New Energy Battery Materials Co., Ltd.) used as the positive electrode active material, 4 parts of carbon black (model: Super-P) used as the conductive material, and 3 parts of binder were added to deionized water to prepare a positive electrode mixture slurry. This positive electrode mixture slurry was coated onto a 12-micron thick aluminum foil current collector, dried, and rolled to form an areal density of 39 mg / cm². 2 Compacted density 2.2 g / cm³ 3 The positive electrode sheet was used to measure its 180° peel force.

[0164] The bonding strength of the positive electrode sheet was tested according to the ASTM-D3330 test method. The equipment and tools were: YISIDA mechanical testing instrument (DS2-50N); 3M tape (model: Scotch 600; 20mm wide); the test results are detailed in Table 2.

[0165] Table 2

[0166]

[0167] As can be seen from the experimental results in Table 2, the binder prepared in this invention exhibits high bonding performance when applied to the positive electrode sheet, at 180°C. o The peel force is not less than 5.0 N / m.

[0168] III. Electrical Performance Testing

[0169] Batteries were fabricated using the binders described in the embodiments and comparative examples of this invention, and their performance was measured. The positive electrode sheet, battery assembly, electrolyte, and processing procedures were all completed using publicly available standard preparation methods and processes.

[0170] 1. Preparation of positive electrode sheet

[0171] Positive electrode sheets were prepared using the binders from Examples 1, 6-7, and Comparative Example 1. The specific methods and results are as follows: 93 parts of lithium iron phosphate compound (Hunan Yuneng New Energy Battery Materials Co., Ltd.) used as the positive electrode active material, 4 parts of carbon black (model: Super-P) used as the conductive material, and 3 parts of binder were added to deionized water to prepare a positive electrode mixture slurry. This positive electrode mixture slurry was coated onto a 12-micron thick aluminum foil current collector, dried, and rolled to form an areal density of 39 mg / cm². 2 Compacted density 2.2 g / cm³ 3 The positive electrode sheet.

[0172] 2. Preparation of negative electrode sheet

[0173] 96 parts of artificial graphite (purchased from Shanshan Co., Ltd.) used as the negative electrode active material, 2 parts of binder (purchased from Zhejiang Zhongke Lide New Materials Co., Ltd., type: negative electrode binder; model: NV-1H), and 2 parts of conductive carbon black (model: super-p) were added to deionized water according to the specified ratio to prepare a negative electrode mixture slurry via a wet process. This negative electrode mixture slurry was coated onto a 6-micron thick copper foil current collector, then dried and rolled to form an areal density of 20 mg / cm². 2 Compacted density 1.70 g / cm³ 3 The negative electrode sheet.

[0174] 3. Battery winding and electrolyte injection

[0175] The electrodes prepared above were used to fabricate a battery with dimensions of 40 mm (thickness) × 63 mm (width) × 79 mm (length). The battery was fabricated by winding the positive electrode, separator, and negative electrode, and packaged using an aluminum-plastic composite. An electrolyte of lithium hexafluorophosphate (LiPF6) with a concentration of 1 mol / L (ethylene carbonate / ethyl methyl carbonate = 1 / 2 (volume ratio)) was injected into the assembled battery, and the battery was vacuum-sealed to obtain a battery ready for activation.

[0176] 4. Battery formation

[0177] After the batteries obtained above were placed in a 45 ℃ environment for 20 h, they were shaped by hot pressing at 95 ℃ for 1 min. The batteries were then placed directly on a formation device without clamping, and formed at 30±2 ℃ with a formation current of 1C for 100 min, resulting in a formation cutoff potential of 4.35 V. They were then placed in a charge / discharge tester for sequential charge / discharge / charge cycles, with a cutoff potential of 3.8 V. Finally, the batteries were degassed and the gas bag was removed to obtain the final battery. This process required only 8 min of hot and cold pressing, without the need for clamping each battery for formation, and the entire formation and capacity testing time was 270 min.

[0178] 5. Battery performance test

[0179] 5.1 Cyclic Performance

[0180] The battery was charged to 4.35 V using a 1C rate current and then kept at a constant voltage of 4.35 V. It was then discharged using a 1C rate current, with a cutoff voltage of 3.0 V, completing one cycle. Results for Example 7 and Comparative Example 1 are shown below. Figure 4 .from Figure 4 As can be seen from the above, the product of Embodiment 7 of the present invention has good cycle performance.

[0181] 5.2 Low-temperature discharge test

[0182] At room temperature (25°C), the battery was charged to 4.35 V at a 0.2C rate and then kept at a constant voltage of 4.35 V. The battery was then placed at a set temperature for 16 hours and discharged at a 1.0C rate, with a cutoff voltage of 2.5 V. Schematic diagrams for Example 7 and Comparative Example 1 are detailed below. Figure 5 The low-temperature capacity, low-temperature median voltage, and retention rate after 6000 cycles for Examples 1, 6, 7, and Comparative Example 1 are detailed in Table 3.

[0183] Table 3

[0184]

[0185] As can be clearly seen from the battery performance test results in Table 3, the battery prepared using the aqueous HTPB binder of the present invention has better performance, with a retention rate of not less than 80% after 6000 cycles.

Claims

1. A water-based HTPB binder for the positive electrode of a lithium battery, characterized in that, The raw materials for preparation include HTPB, allyl isocyanate, acrylic acid monomer, acrylonitrile, acrylamide, acrylate monomers, catalyst, pH adjuster, initiator, surfactant and HTPB solvent; The mass ratio of HTPB, allyl isocyanate, acrylic acid monomer, acrylonitrile, acrylamide, and acrylate monomer is (10-30):(2-15):(15-35):(10-35):(10-20):(5-10). The HTPB includes one or more of type I HTPB, type II HTPB, type III HTPB, and type IV HTPB; The HTPB has a hydroxyl value of 0.4-0.80 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 2000-5000. The acrylic monomer includes at least one of acrylic acid or methacrylic acid; The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40 ℃, and a number-average molecular weight of 3800-4600. The type II HTPB has a hydroxyl value of 0.54-0.64 mmol / g, a viscosity of ≤8.5 Pa•s at 40 ℃, and a number-average molecular weight of 3300-4100. The type III HTPB has a hydroxyl value of 0.65-0.70 mmol / g, a viscosity of ≤4.0 Pa•s at 40 ℃, and a number-average molecular weight of 3000-3600. The type IV HTPB has a hydroxyl value of 0.71-0.80 mmol / g, a viscosity of ≤3.5 Pa•s at 40 ℃, and a number-average molecular weight of 2700-3300. The catalyst comprises one of dibutyltin dilaurate, dioctyltin dilaurate, bismuth octanoate, zinc octanoate, and triethylenediamine; the method for preparing the aqueous HTPB binder for the lithium battery positive electrode is characterized by comprising the following steps: S1. Mix HTPB, allyl isocyanate, catalyst and HTPB solvent, heat to 30-40 ℃, and then stir for 3-5 h to obtain an allylated HTPB solution. Cool to 20-30 ℃ for later use. The pH adjuster and acrylic monomer are mixed and stirred to obtain an acrylate solution, which is then cooled to 20-30℃ for later use. S2. Add surfactant, acrylate solution, acrylonitrile, acrylamide, and acrylate monomer to the allylated HTPB solution, stir at 300-500 rpm for 30-60 min, and then remove the HTPB solvent by vacuum to obtain the reaction emulsion. S3. Inert gas is introduced into the reaction emulsion, the stirring speed is reduced to 100-200 rpm, then the temperature is raised to 40-50℃, the initiator is added dropwise, and the mixture is stirred at 50-90℃ for 6-12 h. After cooling to 20-30℃, water is added for dilution and the mixture is filtered to obtain the water-based HTPB binder for lithium battery positive electrode.

2. The aqueous HTPB binder for the positive electrode of a lithium battery according to claim 1, characterized in that, The acrylate monomers include one or more of butyl acrylate and isooctyl acrylate.

3. The aqueous HTPB binder for the positive electrode of a lithium battery according to claim 1, characterized in that, The pH adjuster mentioned includes sodium hydroxide or potassium hydroxide.

4. The aqueous HTPB binder for the positive electrode of a lithium battery according to claim 1, characterized in that, The initiator includes one of the following: ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, dicumyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxide, dicyclohexyl peroxide, tert-butyl peroxide, cumene hydroperoxide, and tert-butyl hydroperoxide.

Images