Water-based HTPB binder for positive electrode of lithium battery and preparation method of water-based HTPB binder

Abstract

The invention belongs to the technical field of lithium batteries, and particularly relates to a water-based HTPB binder for a positive electrode of a lithium battery and a preparation method of the water-based HTPB binder. The invention provides a high-molecular polymer composite water-based adhesive with a core-shell structure based on an HTPB water-based technology, the high-molecular polymer composite water-based adhesive is prepared by mainly adopting allyl isocyanate to carry out propenylation on HTPB and then carrying out emulsion polymerization on the HTPB, a sodium methacrylate solution, acrylonitrile, acrylamide and an acrylate monomer, and the product is free of VOC (Volatile Organic Compounds) residue and has the advantages of environmental protection, environmental protection and the like. The water-based adhesive is an environment-friendly, non-toxic and pure green water-based adhesive. Compared with the existing water-based positive electrode binder, the water-based HTPB binder provided by the invention has the advantages that the toughness is enhanced by more than two times, and the stripping force is also improved by more than one time. The capacity retention ratio of a battery prepared from the water-based HTPB binder provided by the invention is still more than 80% after 6000 cycles.

Description

Technical Field

[0001] The present invention belongs to the technical field of lithium batteries, and specifically relates to an aqueous HTPB binder for lithium battery cathodes and a preparation method thereof. Background Art

[0002] Binders play a crucial role in the manufacturing process of lithium-ion batteries and have a profound impact on the overall performance of the batteries. In the manufacturing process of lithium-ion battery cathode sheets, organic solvent-based polyvinylidene fluoride (PVDF) is widely used as a binder. For example, Chinese Patent CN114566648B discloses a PVDF lithium battery cathode conductive binder, which can effectively reduce the swelling phenomenon of the cathode system in the electrolyte after use, ensure the stable attachment of active substances to the cathode current collector, and exhibit good resistance to polar organic solvents. However, the fluorine element in PVDF is prone to chemical reactions with materials such as lithium-inserted graphite, which to a certain extent limits the further improvement of the performance of lithium-ion batteries. Therefore, developing a new binder system to optimize the manufacturing process of lithium-ion battery cathodes and improve their performance has become an urgent need for the current industry development.

[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 achievements have been made in the research of aqueous binders in the field of anode materials, and their commercial application in graphite anodes has also been realized, the application of aqueous binders in lithium-ion battery cathodes has not yet been commercialized.

[0004] Currently, aqueous binders for lithium-ion batteries generally have problems such as insufficient flexibility and excessive rigidity, which severely restrict their application in new production processes. Taking lithium iron phosphate anode materials as an example, the conductivity of lithium iron phosphate itself is relatively low, and surface nanocoating technology needs to be used to improve the conductivity. However, the modification process often causes the material to become fluffy, thereby reducing the tap density. Therefore, developing a new binder that can both increase the tap density of lithium battery cathode materials and meet the flexibility requirements of electrodes and the surface conductivity of active substances is of great significance for promoting the development of the lithium-ion battery industry. Summary of the Invention

[0005] In order to obtain an aqueous binder for lithium-ion battery cathodes with high flexibility, the present invention provides an aqueous technology for HTPB (hydroxyl-terminated polybutadiene), which can prepare a new type of polymer composite aqueous binder with a core-shell structure.

[0006] The first aspect of the present invention provides an aqueous HTPB binder for lithium battery cathodes, and its preparation raw materials include HTPB, allyl isocyanate, acrylic monomers, acrylonitrile, acrylamide, acrylate monomers, catalysts, pH regulators, initiators, surfactants, and HTPB solvents.

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

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

[0009] As an implementable case, the hydroxyl value of the HTPB is 0.4 - 0.80 mmol / g, the viscosity at 40 °C is ≤9.5 Pa•s, and the number-average molecular weight is 2000 - 5000.

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

[0011] In the present invention, low-viscosity HTPB is mainly used as the main preparation raw material for the aqueous binder. The low-viscosity HTPB can achieve the required slurry viscosity in less solvent, thereby reducing the solvent usage, lowering costs and environmental pollution. Additionally, the low-viscosity HTPB has better fluidity and is easier to uniformly mix with the electrode material to form a stable slurry; most importantly, the molecular chain length of the low-viscosity HTPB is moderate, making it easier to chemically modify it with allyl isocyanate, acrylic monomers, acrylamide, and acrylate monomers, and the modified polymerization product has a core-shell structure, thereby optimizing the binding performance and mechanical properties of the aqueous binder.

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

[0013] As an implementable case, the acrylate monomer includes one or more of butyl acrylate, isooctyl acrylate, and vinyl acetate.

[0014] As an implementable case, the catalyst includes one of dibutyltin dilaurate, dioctyltin dilaurate, dimethyltin dilaurate, bismuth octoate, zinc octoate, and triethylenediamine.

[0015] Furthermore, the catalyst is dibutyltin dilaurate.

[0016] As an implementable case, the pH regulator includes sodium hydroxide or potassium hydroxide.

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

[0018] In the present invention, potassium hydroxide is selected as the pH regulator, which can react with acrylic monomers through an acid-base reaction to prepare sodium acrylate salt, thereby modifying HTPB and further improving the mechanical properties and bonding properties of the aqueous HTPB binder.

[0019] As an implementable case, the initiator includes one of ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, diisopropylbenzene peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, tert-butyl peroxybenzoate, cumene hydroperoxide, tert-butyl hydroperoxide, and organic amine catalysts.

[0020] As an implementable case, 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 implementable case, the HTPB solvent includes one of dichloromethane, ethyl acetate, methanol, and acetonitrile.

[0024] Furthermore, the HTPB solvent includes dichloromethane.

[0025] The second aspect of the present invention provides a preparation method for an aqueous HTPB binder for a lithium battery cathode, including: S1. Mix HTPB, allyl isocyanate, a catalyst, and an HTPB solvent, heat to 30 - 40 °C, then stir for 3 - 5 h to obtain an allylated HTPB solution, cool to 20 - 30 °C, and set aside. Mix a pH regulator and an acrylic acid monomer and stir to obtain an acrylate solution, cool to 20 - 30 °C, and set aside. S2. Add a surfactant, the acrylate solution, acrylonitrile, acrylamide, and an acrylate monomer to the allylated HTPB solution, stir at 300 - 500 rpm for 30 - 60 min, then evacuate to remove the HTPB solvent to obtain an emulsion for reaction. S3. Pass an inert gas into the emulsion for reaction, reduce the stirring speed to 100 - 200 rpm, then raise the temperature to 40 - 50 °C, dropwise add an initiator, stir at 50 - 90 °C for 6 - 12 h, then cool to 20 - 30 °C, remove monomers, dilute with water, and filter to obtain an aqueous HTPB binder for the positive electrode of a lithium battery.

[0026] In the process of preparing the emulsion for reaction in the present invention, there is no need to additionally use an organic solvent. Instead, by utilizing the water / oil biphasic solubility of acrylonitrile monomer, which has good bidirectional solubility for both oily monomers and polar monomers, and has the dual functions of a reactant and a solvent, it can form a stable emulsion in the aqueous phase, thereby carrying out aqueous phase emulsion polymerization, and at the same time, it can further reduce production costs and VOC emissions.

[0027] The aqueous HTPB binder provided by the present 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 °C; the product has no VOC residue and is an environmentally friendly, non-toxic, and pure green aqueous binder.

[0028] The viscosity control of the aqueous HTPB binder is very important for production and application. In the case of the same solid content, too low viscosity control results in too small a molecular weight of the binder, thus leading to too low adhesion of the binder; while too high viscosity will cause too high a load on the production equipment, and then lead to equipment damage. Therefore, it is necessary to control the viscosity of the aqueous HTPB binder within a reasonable range.

[0029] In the present invention, by strictly controlling the reaction temperature, after the reactants reach a certain temperature, a cooling step is taken to control the degree of polymerization of the product, so that when the aqueous binder is at 40 °C, under the conditions of a solid content of 10.0 wt% and a pH value of 6.0 - 8.0, its viscosity is within the range of 9.0 - 20.0 Pa•s.

[0030] Beneficial effects (1) The novel aqueous HTPB binder provided by the present invention adopts the aqueous technology, avoiding the environmental pollution problems of traditional organic solvent-based binders (such as the PVDF system). It is an environmentally friendly, non-toxic, and pure green binder, especially suitable for use in the cathode materials of lithium-ion batteries.

[0031] (2) The present invention mainly designs through a core-shell structure, where the hydrophobic core is HTPB and the hydrophilic shell is a 2-polyacrylic acid polymer chain, significantly enhancing the flexibility of the prepared aqueous HTPB binder, increasing the elongation at break, and also significantly improving the peel strength (more than doubling that of existing aqueous binders). It can better adapt to the volume changes of electrode materials during charge and discharge, preventing electrode cracking or detachment.

[0032] (3) For the battery prepared using the aqueous HTPB binder provided by the present invention, after 6000 cycles, the capacity retention rate is still above 85%, showing excellent cycle stability, especially suitable for high-energy density batteries.

[0033] (4) The aqueous HTPB binder provided by the present invention can still maintain good discharge performance at a low temperature of -20°C. The low-temperature discharge capacity and median voltage of the battery are superior to those of traditional binders, and it is suitable for use in a wide temperature range.

[0034] (5) In the process of preparing the emulsion for the reaction of the present invention, no additional organic solvents are required. Instead, the water / oil biphasic solubility of acrylonitrile monomers is utilized to effectively reduce the production cost and VOC emissions, without affecting the binding performance and electrical properties of the aqueous binder. Description of the Drawings

[0035] Figure 1 It is a schematic diagram of the chemical reactions involved in the preparation process of the aqueous HTPB binder.

[0036] Figure 2 It is a schematic diagram of the core-shell structure model of the aqueous HTPB binder, where 1 is the HTPB hydrophobic core and 2 is the 2-polyacrylic acid polymer chain hydrophilic shell.

[0037] Figure 3 It is the SEM image of the aqueous HTPB binder prepared in Example 7, with a scale of 1 μm.

[0038] Figure 4 It is a schematic diagram of the battery cycle performance of the aqueous HTPB binder prepared in Example 7 and Comparative Example 1 applied in the battery. Test conditions: Charge the battery at a current of 1C to 4.35 V and hold the voltage at 4.35 V; then discharge the battery at a current of 1C, with a cut-off voltage of 3.0 V to complete one cycle.

[0039] Figure 5Schematic diagram of the low-temperature discharge performance of the battery using the aqueous HTPB binder prepared in Example 7 and Comparative Example 1. Test conditions: Discharge at a rate of 1C to 2.5 V at -20 °C. Detailed implementation method

[0040] Example 1 In the first aspect of this example, an aqueous HTPB binder for the positive electrode of a lithium battery is provided. The preparation raw materials are as follows by mass fraction: 20 parts of type I HTPB, 5 parts of allyl isocyanate, 30 parts of methacrylic acid, 20 parts of acrylonitrile, 20 parts of acrylamide, 5 parts of butyl acrylate, 0.2 part of dibutyltin dilaurate, 9 parts of an aqueous sodium hydroxide solution with a mass concentration of 46.4 wt%, 0.1 part of an aqueous ammonium persulfate solution with a mass concentration of 1 wt%, 0.4 part of polyoxyethylene nonylphenol ether-14, and 40 parts of dry dichloromethane.

[0041] The polyoxyethylene nonylphenol ether-14 is purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0042] The hydroxyl value of the type I HTPB is 0.47 - 0.53 mmol / g, the viscosity at 40 °C is ≤9.5 Pa•s, and the number-average molecular weight is 3800 - 4600. It is purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0043] In the second aspect of this example, a preparation method of an aqueous HTPB binder for the positive electrode of a lithium battery is provided, specifically as follows: S1. Mix type I HTPB, allyl isocyanate, dibutyltin dilaurate, and dichloromethane, heat to 35 °C, and then stir for 3 h to obtain an allylated HTPB solution. Cool to 25 °C and set aside; Mix the aqueous sodium hydroxide solution and methacrylic acid and stir to obtain a sodium methacrylate solution. Cool to 25 °C and set aside; S2. Add polyoxyethylene nonylphenol ether-14, the sodium acrylate solution, acrylonitrile, acrylamide, and butyl acrylate to the allylated HTPB solution in sequence, stir at 300 rpm for 30 min, and then evacuate to remove dichloromethane to obtain a reaction emulsion; S3. Pass nitrogen into the reaction emulsion, reduce the stirring speed to 100 rpm, then heat to 50 °C, dropwise add the aqueous ammonium persulfate solution, stir at 80 °C for 9 h, then cool to 25 °C, remove monomers, dilute with water, and filter to obtain the aqueous HTPB binder for the positive electrode of a lithium battery.

[0044] The aqueous binder prepared in this example has a pH value of 7.0, a viscosity of 10.3 Pa•s, and an appearance of white latex at 40 °C and a solid content of 8.0 wt%.

[0045] Example 2 In the first aspect of this example, an aqueous HTPB binder for the positive electrode of a lithium battery is provided. The preparation raw materials are as follows by mass fraction: 20 parts of type II HTPB, 5 parts of allyl isocyanate, 30 parts of methacrylic acid, 20 parts of acrylonitrile, 20 parts of acrylamide, 5 parts of butyl acrylate, 0.2 part of dibutyltin dilaurate, 9 parts of an aqueous sodium hydroxide solution with a mass concentration of 46.4 wt%, 0.1 part of an aqueous ammonium persulfate solution with a mass concentration of 1 wt%, 0.4 part of polyoxyethylene nonylphenol ether-14, and 40 parts of dry dichloromethane.

[0046] The polyoxyethylene nonylphenol ether-14 is purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0047] The hydroxyl value of the type II HTPB is 0.54 - 0.64 mmol / g, the viscosity at 40 °C is ≤8.5 Pa•s, the number average molecular weight is 3300 - 4100, and it is purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0048] In the second aspect of this example, a preparation method of an aqueous HTPB binder for the positive electrode of a lithium battery is provided, specifically as follows: S1. Mix type II HTPB, allyl isocyanate, dibutyltin dilaurate, and dichloromethane, heat to 35 °C, then stir for 3 h to obtain an allylated HTPB solution, cool to 25 °C, and set aside; Mix the aqueous sodium hydroxide solution and methacrylic acid and stir to obtain a sodium methacrylate solution, cool to 25 °C, and set aside; S2. Add polyoxyethylene nonylphenol ether-14, the sodium methacrylate solution, acrylonitrile, acrylamide, and butyl acrylate to the allylated HTPB solution in sequence, stir at 300 rpm for 30 min, then evacuate to remove dichloromethane to obtain an emulsion for reaction; S3. Pass nitrogen into the emulsion for reaction, reduce the stirring speed to 100 rpm, then heat to 50 °C, dropwise add the aqueous ammonium persulfate solution, stir at 80 °C for 9 h, then cool to 25 °C, remove monomers, dilute with water, and filter to obtain the aqueous HTPB binder for the positive electrode of a lithium battery.

[0049] The aqueous binder prepared in this example has a pH value of 7.1, a viscosity of 10.1 Pa•s, and an appearance of white latex at 40 °C and a solid content of 10.0 wt%.

[0050] Example 3 In the first aspect of this example, an aqueous HTPB binder for the positive electrode of a lithium battery is provided. The preparation raw materials are as follows by mass fraction: 20 parts of type III HTPB, 5 parts of allyl isocyanate, 30 parts of methacrylic acid, 20 parts of acrylonitrile, 20 parts of acrylamide, 5 parts of butyl acrylate, 0.2 part of dibutyltin dilaurate, 9 parts of an aqueous sodium hydroxide solution with a mass concentration of 46.4 wt%, 0.1 part of an aqueous ammonium persulfate solution with a mass concentration of 1 wt%, 0.4 part of polyoxyethylene nonylphenol ether-14, and 40 parts of dry dichloromethane.

[0051] The hydroxyl value of the described type III HTPB is 0.65 - 0.70 mmol / g, the viscosity at 40 °C is ≤ 4.0 Pa•s, the number-average molecular weight is 3000 - 3600, and it is purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

[0052] The polyoxyethylene nonylphenol ether-14 is purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0053] In the second aspect of this example, a preparation method of an aqueous HTPB binder for the positive electrode of a lithium battery is provided, specifically as follows: S1. Mix type III HTPB, allyl isocyanate, dibutyltin dilaurate, and dichloromethane, heat to 35 °C, then stir for 3 h to obtain an allylated HTPB solution, cool to 25 °C, and set aside; Mix the aqueous sodium hydroxide solution and methacrylic acid and stir to obtain a sodium methacrylate solution, cool to 25 °C, and set aside; S2. Sequentially add polyoxyethylene nonylphenol ether-14, the sodium methacrylate solution, acrylonitrile, acrylamide, and butyl acrylate to the allylated HTPB solution, stir at 300 rpm for 30 min, then evacuate to remove dichloromethane to obtain an emulsion for reaction; S3. Pass nitrogen into the emulsion for reaction, reduce the stirring speed to 100 rpm, then heat to 50 °C, dropwise add the aqueous ammonium persulfate solution, stir at 80 °C for 9 h, then cool to 25 °C, remove monomers, dilute with water, and filter to obtain the aqueous HTPB binder for the positive electrode of a lithium battery.

[0054] The aqueous binder prepared in this example has a pH value of 7.1, a viscosity of 9.9 Pa•s, and an appearance of a white latex at 40 °C with a solid content of 10.0 wt%.

[0055] Example 4 The first aspect of this example provides an aqueous HTPB binder for a lithium battery positive electrode, wherein the raw materials for its preparation are, in parts by mass, 20 parts of type IV HTPB, 5 parts of propylene isocyanate, 30 parts of methacrylic acid, 20 parts of acrylonitrile, 20 parts of acrylamide, 5 parts of butyl acrylate, 0.2 parts of dibutyltin dilaurate, 9 parts of a sodium hydroxide aqueous solution with a mass concentration of 46.4wt%, 0.1 parts of an ammonium persulfate aqueous solution with a mass concentration of 1wt%, 0.4 parts of polyoxyethylene nonylphenol ether-14 and 40 parts of dry dichloromethane.

[0056] The IV type HTPB has a hydroxyl value of 0.71-0.80 mmol / g, a viscosity of ≤3.5 Pa•s at 40°C, and a number average molecular weight of 2700-3300, and is purchased from Tianyuan Aerospace Materials (Yingkou) Technology Co., Ltd.

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

[0058] The second aspect of this example provides a method for preparing an aqueous HTPB binder for a lithium battery positive electrode, specifically: S1. Mix type IV HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain an propylene-containing HTPB solution, cool to 25°C, and set aside; Mixing the sodium hydroxide aqueous solution and methacrylic acid to obtain a sodium methacrylic acid salt solution, cooling the solution to 25° C., and setting it aside; S2, adding polyoxyethylene nonylphenol ether-14, acrylic acid sodium salt solution, acrylonitrile, acrylamide, and butyl acrylate to the propylene-treated HTPB solution in sequence, stirring at 300 rpm for 30 min, and then vacuuming to remove dichloromethane to obtain a reaction emulsion; S3. Nitrogen is introduced into the reaction emulsion again, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 °C, and an aqueous ammonium persulfate solution is added dropwise, and stirred at 80 °C for 9 h. Then, after cooling to 25 °C, the mixture is stripped, diluted with water, and filtered to obtain a water-based HTPB binder for lithium battery positive electrode.

[0059] The water-based binder prepared in this example has a pH value of 7.0 and a viscosity of 9.8 Pa•s at 40° C. and a solid content of 10.0 wt %, and has an appearance of white latex.

[0060] Example 5 The first aspect of this example provides an aqueous HTPB binder for a lithium battery positive electrode, wherein the raw materials for its preparation are, in parts by mass, 10 parts of type I HTPB, 2.5 parts of propylene isocyanate, 30 parts of methacrylic acid, 32.5 parts of acrylonitrile, 20 parts of acrylamide, 5 parts of butyl acrylate, 0.1 part of dibutyltin dilaurate, 9.8 parts of a sodium hydroxide aqueous solution with a mass concentration of 46.4wt%, 0.1 part of an ammonium persulfate aqueous solution with a mass concentration of 1wt%, 0.2 part of polyoxyethylene nonylphenol ether-14 and 20 parts of dry dichloromethane.

[0061] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40°C, and a number average molecular weight of 3800-4600, and is purchased from Tianyuan Aerospace Materials (Yingkou) Technology Co., Ltd.

[0062] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0063] The second aspect of this example provides a method for preparing an aqueous HTPB binder for a lithium battery positive electrode, specifically: S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain an propylene-containing HTPB solution, cool to 25°C, and set aside; Mixing the sodium hydroxide aqueous solution and methacrylic acid to obtain a sodium methacrylic acid salt solution, cooling the solution to 25° C., and setting it aside; S2, adding polyoxyethylene nonylphenol ether-14, acrylic acid sodium salt solution, acrylonitrile, acrylamide, and butyl acrylate to the propylene-treated HTPB solution in sequence, stirring at 300 rpm for 30 min, and then vacuuming to remove dichloromethane to obtain a reaction emulsion; S3. Nitrogen is introduced into the reaction emulsion again, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 °C, and an aqueous ammonium persulfate solution is added dropwise, and stirred at 80 °C for 9 h. Then, after cooling to 25 °C, the mixture is stripped, diluted with water, and filtered to obtain a water-based HTPB binder for lithium battery positive electrode.

[0064] The water-based binder prepared in this example has a pH value of 7.1 and a viscosity of 11.2 Pa•s at 40°C and a solid content of 10.0 wt%, and has an appearance of white latex.

[0065] Example 6 The first aspect of this example provides an aqueous HTPB binder for a lithium battery positive electrode, wherein the raw materials for its preparation are, in parts by mass, 15 parts of type I HTPB, 3.75 parts of propylene isocyanate, 30 parts of methacrylic acid, 26.5 parts of acrylonitrile, 20 parts of acrylamide, 5 parts of butyl acrylate, 0.15 parts of dibutyltin dilaurate, 9 parts of a sodium hydroxide aqueous solution with a mass concentration of 46.4wt%, 0.1 parts of an ammonium persulfate aqueous solution with a mass concentration of 1wt%, 0.3 parts of polyoxyethylene nonylphenol ether-14 and 30 parts of dry dichloromethane.

[0066] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40°C, and a number average molecular weight of 3800-4600, and is purchased from Tianyuan Aerospace Materials (Yingkou) Technology Co., Ltd.

[0067] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0068] The second aspect of this example provides a method for preparing an aqueous HTPB binder for a lithium battery positive electrode, specifically: S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain an propylene-containing HTPB solution, cool to 25°C, and set aside; Mixing the sodium hydroxide aqueous solution and methacrylic acid to obtain a sodium methacrylic acid salt solution, cooling the solution to 25° C., and setting it aside; S2, adding polyoxyethylene nonylphenol ether-14, acrylic acid sodium salt solution, acrylonitrile, acrylamide, and butyl acrylate to the propylene-treated HTPB solution in sequence, stirring at 300 rpm for 30 min, and then vacuuming to remove dichloromethane to obtain a reaction emulsion; S3. Nitrogen is introduced into the reaction emulsion again, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 °C, and an aqueous ammonium persulfate solution is added dropwise, and stirred at 80 °C for 9 h. Then, after cooling to 25 °C, the mixture is stripped, diluted with water, and filtered to obtain a water-based HTPB binder for lithium battery positive electrode.

[0069] The water-based binder prepared in this example has a pH value of 7.1 and a viscosity of 11.2 Pa•s at 40°C and a solid content of 10.0 wt%, and has an appearance of white latex.

[0070] Example 7 The first aspect of this example provides an aqueous HTPB binder for a lithium battery positive electrode, wherein the raw materials for its preparation are, in parts by mass, 25 parts of type I HTPB, 6.25 parts of propylene isocyanate, 23.75 parts of methacrylic acid, 20 parts of acrylonitrile, 20 parts of acrylamide, 5 parts of butyl acrylate, 0.25 parts of dibutyltin dilaurate, 7.2 parts of a sodium hydroxide aqueous solution with a mass concentration of 46.4wt%, 0.1 parts of an ammonium persulfate aqueous solution with a mass concentration of 1wt%, 0.5 parts of polyoxyethylene nonylphenol ether-14 and 50 parts of dry dichloromethane.

[0071] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40°C, and a number average molecular weight of 3800-4600, and is purchased from Tianyuan Aerospace Materials (Yingkou) Technology Co., Ltd.

[0072] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0073] The second aspect of this example provides a method for preparing an aqueous HTPB binder for a lithium battery positive electrode, specifically: S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain an propylene-containing HTPB solution, cool to 25°C, and set aside; Mixing the sodium hydroxide aqueous solution and methacrylic acid to obtain a sodium methacrylic acid salt solution, cooling the solution to 25° C., and setting it aside; S2, adding polyoxyethylene nonylphenol ether-14, acrylic acid sodium salt solution, acrylonitrile, acrylamide, and butyl acrylate to the propylene-treated HTPB solution in sequence, stirring at 300 rpm for 30 min, and then vacuuming to remove dichloromethane to obtain a reaction emulsion; S3. Nitrogen is introduced into the reaction emulsion again, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 °C, and an aqueous ammonium persulfate solution is added dropwise, and stirred at 80 °C for 9 h. Then, after cooling to 25 °C, the mixture is stripped, diluted with water, and filtered to obtain a water-based HTPB binder for lithium battery positive electrode.

[0074] The water-based binder prepared in this example has a pH value of 7.0 and a viscosity of 10.6 Pa•s at 40°C and a solid content of 10.0 wt%, and has an appearance of white latex.

[0075] The SEM image of the water-based HTPB binder prepared in this example is as follows: Figure 3 shown.

[0076] Example 8 In the first aspect of this example, an aqueous HTPB binder for the positive electrode of a lithium battery is provided. The preparation raw materials, by mass fraction, are specifically as follows: 30 parts of type I HTPB, 7.5 parts of allyl isocyanate, 20 parts of methacrylic acid, 20 parts of acrylonitrile, 17.5 parts of acrylamide, 5 parts of butyl acrylate, 0.3 part of dibutyltin dilaurate, 6 parts of an aqueous sodium hydroxide solution with a mass concentration of 46.4 wt%, 0.1 part of an aqueous ammonium persulfate solution with a mass concentration of 1 wt%, 0.6 part of polyoxyethylene nonylphenol ether - 14, and 60 parts of dry dichloromethane.

[0077] The hydroxyl value of the described type I HTPB is 0.47 - 0.53 mmol / g, the viscosity at 40 °C is ≤9.5 Pa•s, the number average molecular weight is 3800 - 4600, and it is purchased from Tianyuan Aviation Materials (Yingkou) Technology Co., Ltd.

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

[0079] In the second aspect of this example, a preparation method of an aqueous HTPB binder for the positive electrode of a lithium battery is provided, specifically as follows: S1. Mix type I HTPB, allyl isocyanate, dibutyltin dilaurate, and dichloromethane, heat to 35 °C, then stir for 3 h to obtain an allylated HTPB solution, cool to 25 °C, and set aside; Mix the aqueous sodium hydroxide solution and methacrylic acid and stir to obtain a sodium methacrylate solution, cool to 25 °C, and set aside; S2. Sequentially add polyoxyethylene nonylphenol ether - 14, the sodium methacrylate solution, acrylonitrile, acrylamide, butyl acrylate to the allylated HTPB solution, stir at 300 rpm for 30 min, then evacuate to remove dichloromethane to obtain an emulsion for reaction; S3. Pass nitrogen into the emulsion for reaction, reduce the stirring speed to 100 rpm, then heat to 50 °C, dropwise add the aqueous ammonium persulfate solution, stir at 80 °C for 9 h, then cool to 25 °C, remove monomers, add water for dilution, and filter to obtain the aqueous HTPB binder for the positive electrode of a lithium battery.

[0080] The aqueous binder prepared in this example has a pH value of 7.1, a viscosity of 12.1 Pa•s, and an appearance of white latex at 40 °C and a solid content of 10.0 wt%.

[0081] Example 9 The first aspect of this example provides an aqueous HTPB binder for a lithium battery positive electrode, wherein the raw materials for its preparation are, in parts by mass, 20 parts of type I HTPB, 5 parts of propylene isocyanate, 35 parts of methacrylic acid, 20 parts of acrylonitrile, 15 parts of acrylamide, 5 parts of butyl acrylate, 0.2 parts of dibutyltin dilaurate, 7 parts of a sodium hydroxide aqueous solution with a mass concentration of 46.4wt%, 0.1 parts of an ammonium persulfate aqueous solution with a mass concentration of 1wt%, 0.4 parts of polyoxyethylene nonylphenol ether-14 and 40 parts of dry dichloromethane.

[0082] The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40°C, and a number average molecular weight of 3800-4600, and is purchased from Tianyuan Aerospace Materials (Yingkou) Technology Co., Ltd.

[0083] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0084] The second aspect of this example provides a method for preparing an aqueous HTPB binder for a lithium battery positive electrode, specifically: S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain an propylene-containing HTPB solution, cool to 25°C, and set aside; Mixing the sodium hydroxide aqueous solution and methacrylic acid to obtain a sodium methacrylic acid salt solution, cooling the solution to 25° C., and setting it aside; S2, adding polyoxyethylene nonylphenol ether-14, acrylic acid sodium salt solution, acrylonitrile, acrylamide, and butyl acrylate to the propylene-treated HTPB solution in sequence, stirring at 300 rpm for 30 min, and then vacuuming to remove dichloromethane to obtain a reaction emulsion; S3. Nitrogen is introduced into the reaction emulsion again, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 °C, and an aqueous ammonium persulfate solution is added dropwise, and stirred at 80 °C for 9 h. Then, after cooling to 25 °C, the mixture is stripped, diluted with water, and filtered to obtain a water-based HTPB binder for lithium battery positive electrode.

[0085] The water-based binder prepared in this example has a pH value of 7.0 and a viscosity of 10.6 Pa•s at 40°C and a solid content of 10.0 wt%, and has an appearance of white latex.

[0086] Example 10 The first aspect of this example provides an aqueous HTPB binder for a lithium battery positive electrode, wherein the raw materials for its preparation are, in parts by mass, 20 parts of type I HTPB, 5 parts of propylene isocyanate, 35 parts of methacrylic acid, 20 parts of acrylonitrile, 10 parts of acrylamide, 10 parts of butyl acrylate, 0.2 parts of dibutyltin dilaurate, 7 parts of a sodium hydroxide aqueous solution with a mass concentration of 46.4wt%, 0.1 parts of an ammonium persulfate aqueous solution with a mass concentration of 1wt%, 0.4 parts of polyoxyethylene nonylphenol ether-14 and 40 parts of dry 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°C, and a number average molecular weight of 3800-4600, and is purchased from Tianyuan Aerospace 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 an aqueous HTPB binder for a lithium battery positive electrode, specifically: S1. Mix type I HTPB, propylene isocyanate, dibutyltin dilaurate and dichloromethane, heat to 35°C, and then stir for 3 h to obtain an propylene-containing HTPB solution, cool to 25°C, and set aside; Mixing the sodium hydroxide aqueous solution and methacrylic acid to obtain a sodium methacrylic acid salt solution, cooling the solution to 25° C., and setting it aside; S2, adding polyoxyethylene nonylphenol ether-14, acrylic acid sodium salt solution, acrylonitrile, acrylamide, and butyl acrylate to the propylene-treated HTPB solution in sequence, stirring at 300 rpm for 30 min, and then vacuuming to remove dichloromethane to obtain a reaction emulsion; S3. Nitrogen is introduced into the reaction emulsion again, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 50 °C, and an aqueous ammonium persulfate solution is added dropwise, and stirred at 80 °C for 9 h. Then, after cooling to 25 °C, the mixture is stripped, diluted with water, and filtered to obtain a water-based HTPB binder for lithium battery positive electrode.

[0090] The water-based binder prepared in this example has a pH value of 7.1 and a viscosity of 11.5 Pa•s at 40°C and a solid content of 10.0 wt%, and has an appearance of white latex.

[0091] The chemical reaction diagrams involved in the preparation of the water-based HTPB binder in Examples 1-10 are as follows: Figure 1 shown.

[0092] Schematic diagram of the core-shell structure model of the water-based HTPB binder of Example 1-10 is shown inFigure 2 As shown, 1-HTPB hydrophobic core, 2-polyacrylic acid polymer chain hydrophilic shell.

[0093] Comparative Example 1 The first aspect of this example provides an aqueous binder for a lithium battery positive electrode, wherein the raw materials for its preparation are, in parts by mass, 45 parts of methacrylic acid, 20 parts of acrylonitrile, 15 parts of acrylamide, 20 parts of butyl acrylate, 5 parts of a sodium hydroxide aqueous solution with a mass concentration of 46.4wt%, 0.1 parts of an ammonium persulfate aqueous solution with a mass concentration of 1wt%, and 0.4 parts of polyoxyethylene nonylphenol ether-14.

[0094] The polyoxyethylene nonylphenol ether-14 was purchased from Sigma-Aldrich, CAS: 9016-45-9.

[0095] The second aspect of this example provides a method for preparing an aqueous binder for a lithium battery positive electrode, specifically: S1, mixing sodium hydroxide aqueous solution, deionized water and methacrylic acid to obtain a sodium acrylate solution, cooling it to 25°C and setting it aside; S2, mixing acrylonitrile, acrylamide, butyl acrylate and polyoxyethylene nonylphenol ether-14, and stirring at 300 rpm for 30 min to obtain a reaction emulsion; S3. Nitrogen is introduced into the reaction emulsion again, the stirring speed is reduced to 100 rpm, and then the temperature is raised to 60°C, and an aqueous ammonium persulfate solution is added dropwise, and stirred at 80°C for 9 h. Then, after cooling to 25°C, the mixture is stripped, diluted with water, and filtered to obtain a water-based HTPB binder for lithium battery positive electrode.

[0096] The water-based binder prepared in this example has a pH value of 7.0 and a viscosity of 6.1 Pa•s at 40°C and a solid content of 15.0 wt%, and has an appearance of white latex.

[0097] Performance Testing 1. Elongation at break test of adhesive film Examples 1-10 and Comparative Example 1 corresponding binder films were prepared with reference to ASTM standard D638, and the elongation at break of the binder films was tested. There should be 5 samples for each selected strain rate (the experimental results are the average of 5 groups). The experiment was carried out under constant temperature and humidity conditions, and the specific conditions were: 25 °C, 40% RH (humidity); the test results are shown in Table 1. Standard process steps for preparing the binder film sample: Weigh 100 g of the binder sample into a polytetrafluoroethylene mold (the specifications of length, width and height are: 250×40×10 mm), and then place the mold containing the sample statically on a horizontal table. After the binder sample in the mold levels off, place this mold containing the binder sample in an oven with a horizontal tray, and dry the moisture in the binder at 60 °C to obtain the binder film. Select a flawless binder film, cut it into a film sample for testing according to the specifications with reference to the ASTM standard, and store it under constant temperature and humidity for testing.

[0098] Table 1

[0099] From the experimental results in Table 1, it can be seen that the elongation at break of the film of the aqueous HTPB binder prepared by the present invention is greater than 100%, and it has high flexibility.

[0100] II. 180° peel strength test The binders of Examples 1-10 and Comparative Example 1 were used to prepare positive electrode plates, and 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 the binder were added to deionized water to prepare a positive electrode mixture slurry. The positive electrode mixture slurry was coated on an aluminum foil current collector with a thickness of 12 μm, dried and roll-pressed to form a positive electrode plate with a surface density of 39 mg / cm 2 , and a compaction density of 2.2 g / cm 3 ; its 180° peel strength was measured.

[0101] The adhesion test of the positive electrode plate was carried out with reference to the ASTM-D3330 test method. Equipment and tools: YISIDA mechanical tester (DS2-50N); 3M tape (model: Scotch 600; 20 mm wide); the test results are shown in Table 2.

[0102] Table 2

[0103] From the experimental results in Table 2, it can be seen that the binder prepared by the present invention has high adhesion performance when applied to the positive electrode plate, and the 180 o peel strength is not less than 5.0 N / m.

[0104] III. Electrical Property Tests The binders of the examples and comparative examples in the present invention were used to prepare batteries, and their properties were measured. The positive electrode sheets, battery assembly, electrolyte, processing procedures, etc. were all completed using the publicly disclosed standard preparation methods and procedures.

[0105] 1. Preparation of Positive Electrode Sheets The binders of Example 1, Examples 6 - 7 and Comparative Example 1 were used to prepare positive electrode sheets. 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 the positive electrode mixture slurry. The positive electrode mixture slurry was coated on an aluminum foil current collector with a thickness of 12 μm, dried and roll - pressed to form a positive electrode sheet with a surface density of 39 mg / cm 2 , and a tap density of 2.2 g / cm 3 .

[0106] 2. Preparation of Negative Electrode Sheets 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 ratio, and the negative electrode mixture slurry was prepared by a wet process. The negative electrode mixture slurry was coated on a copper foil current collector with a thickness of 6 μm, and then dried and roll - pressed; a negative electrode sheet with a surface density of 20 mg / cm 2 , and a tap density of 1.70 g / cm 3 was formed.

[0107] 3. Battery Winding and Electrolyte Injection The electrodes prepared above were used to prepare a battery with specifications of 40 mm (thickness) × 63 mm (width) × 79 mm (length). The battery was made by winding the positive electrode, separator and negative electrode, and the battery was packaged using aluminum - plastic composite. An electrolyte (ethylene carbonate / ethyl methyl carbonate = 1 / 2 (volume ratio)) with a concentration of 1 mole / liter of lithium hexafluorophosphate (LiPF 6 ) was injected into the assembled battery, and it was evacuated and sealed to obtain a battery ready to enter the activation state.

[0108] 4. Battery Formation After leaving the obtained battery still in an environment of 45 °C for 20 h, the battery is shaped by hot pressing at 95 °C for 1 min. The battery is directly placed on formation equipment without being clamped by a fixture, and formation is carried out on the battery in an environment of 30±2 °C, the formation current is 1C, the formation time is 100 min, and the formation cut-off potential is 4.35 V. Then it is placed in a charge-discharge tester to perform charge / discharge / charge cycles in sequence, the cut-off potential is 3.8 V, and then degassing and cutting off the gas bag operation are carried out on the battery to obtain the battery. In this process, only 8 min of hot and cold pressing is required, and no other fixtures are needed to clamp and form each battery, and the entire formation and grading time is 270 min.

[0109] 5. Battery performance test 5.1 Cycling performance Charge the battery at a current of 1C rate to 4.35 V and hold at a constant voltage of 4.35 V; then discharge the battery at a current of 1C rate, and the cut-off voltage is 3.0 V to complete one cycle. The results of Example 7 and Comparative Example 1 are shown in Figure 4 . From Figure 4 it can be seen that the product of Example 7 of the present invention has good cycling performance.

[0110] 5.2 Low-temperature discharge test Under the condition of normal temperature of 25 °C, charge the battery at a current of 0.2C rate to 4.35 V and hold at a constant voltage of 4.35 V; then place the battery at the set temperature for 16 h and discharge at a current of 1.0C rate at the corresponding temperature, and the cut-off voltage is 2.5 V. The schematic diagrams of Example 7 and Comparative Example 1 are shown in detail in Figure 5 ; The low-temperature capacity, low-temperature median voltage and 6000-cycle retention rate of Example 1, Example 6, Example 7 and Comparative Example 1 are shown in Table 3.

[0111] Table 3

[0112] It can be clearly seen from the battery performance test results in Table 3 that the battery prepared by using the aqueous HTPB binder of the present invention has better performance, and the retention rate is not less than 80% after 6000 cycles.

Claims

1. A water-based HTPB binder for lithium battery positive electrode, characterized in that: The preparation raw materials include HTPB, propylene isocyanate, acrylic acid monomer, acrylonitrile, acrylamide, acrylic acid ester monomer, catalyst, pH regulator, initiator, surfactant and HTPB solvent; The mass ratio of HTPB, propylene isocyanate, acrylic acid monomer, acrylonitrile, acrylamide and acrylic acid ester 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°C, and a number average molecular weight of 2000-5000; The acrylic acid monomer includes at least one of acrylic acid or methacrylic acid.

2. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The type I HTPB has a hydroxyl value of 0.47-0.53 mmol / g, a viscosity of ≤9.5 Pa•s at 40°C, and a number average molecular weight of 3800-4600.

3. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The type II HTPB has a hydroxyl value of 0.54-0.64 mmol / g, a viscosity of ≤8.5 Pa•s at 40° C., and a number average molecular weight of 3300-4100.

4. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The type III HTPB has a hydroxyl value of 0.65-0.70 mmol / g, a viscosity of ≤4.0 Pa•s at 40° C., and a number average molecular weight of 3000-3600.

5. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The type IV HTPB has a hydroxyl value of 0.71-0.80 mmol / g, a viscosity of ≤3.5 Pa•s at 40° C., and a number average molecular weight of 2700-3300.

6. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The acrylic acid ester monomers include one or more of butyl acrylate, isooctyl acrylate and vinyl acetate.

7. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The catalyst comprises one of dibutyltin dilaurate, dioctyltin dilaurate, dimethyltin dilaurate, bismuth octoate, zinc octoate and triethylenediamine.

8. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The pH regulator includes sodium hydroxide or potassium hydroxide.

9. The aqueous HTPB binder for lithium battery positive electrode according to claim 1, characterized in that: The initiator includes one of ammonium persulfate, potassium persulfate, sodium persulfate, benzoyl peroxide, lauroyl peroxide, di-tert-butyl peroxide, diisopropyl peroxide, methyl ethyl ketone peroxide, cyclohexanone peroxide, diisopropyl peroxydicarbonate, dicyclohexyl peroxydicarbonate, tert-butyl perbenzoate, isopropyl hydroperoxide, tert-butyl hydroperoxide, and an organic amine catalyst.

10. A method for preparing an aqueous HTPB binder for a lithium battery positive electrode according to any one of claims 1 to 9, characterized in that: The following steps are involved: S1. Mix HTPB, propylene isocyanate, a catalyst and a HTPB solvent, heat to 30-40°C, and then stir for 3-5h to obtain an propylene-containing HTPB solution, cool to 20-30°C, and set aside; Mixing the pH adjuster and the acrylic acid monomer to obtain an acrylic acid salt solution, cooling the solution to 20-30° C., and setting aside; S2, adding a surfactant, an acrylate solution, acrylonitrile, acrylamide, and an acrylate monomer to the propylene-modified HTPB solution, stirring at 300-500 rpm for 30-60 min, and then vacuuming to remove the HTPB solvent to obtain an emulsion for reaction; S3. Introduce inert gas into the reaction emulsion again, reduce the stirring speed to 100-200 rpm, then raise the temperature to 40-50°C, add initiator dropwise, stir at 50-90°C for 6-12 h, then cool to 20-30°C, dilute with water, filter, and obtain the aqueous HTPB binder for lithium battery positive electrode.

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