Powder battery binder, preparation method and application thereof

Abstract

The application provides a preparation method and application of a powder battery binder. The preparation of the powder battery binder comprises the following steps: S1: mixing an aqueous phase mixed solution and an oil phase solution, and then performing inverse suspension polymerization to obtain a suspension; S2: performing post-crosslinking treatment on the suspension to obtain a modified suspension; and S3: removing residual oil phase and water from the modified suspension, and then drying to obtain the powder battery binder. The powder battery binder can avoid the introduction of moisture into positive and negative active materials of a battery, so that the safety performance of the battery is improved, can be used as a binder for the positive and negative active materials, and can reduce the transportation cost of the binder.

Description

Technical Field

[0001] This invention belongs to the field of polymer materials, specifically relating to a method for preparing a powder battery binder and its application. Background Technology

[0002] Lithium-ion batteries are widely used in electronic products, electric vehicles, and energy storage devices due to their advantages such as high energy density, long cycle life, and ease of design. As the application scenarios and functional requirements of various products become increasingly diverse, the market is placing higher demands on the energy density, reliability, and cost of lithium-ion batteries. Especially in the pursuit of high energy density lithium batteries, the demand for silicon-carbon materials is growing, and these materials place even stricter requirements on the battery's negative electrode binder.

[0003] Negative electrode binders are important polymer materials in lithium-ion batteries. Their main function is to adhere the negative electrode active material (graphite, silicon carbide, silicon, etc.) and conductive agents to the current collector. Although the amount of binder used is not large (about 1.5-5% of the negative electrode material), its performance has a significant impact on the performance of lithium batteries, such as specific capacity, coulombic efficiency, internal resistance, and cycle life.

[0004] Currently, the most widely used negative electrode binder is styrene-butadiene rubber solution (SBR), which requires the addition of carboxymethyl cellulose (CMC) as a thickening and dispersing agent during use. The material composition limits the content of polar functional groups such as carboxyl, ester, and cyano groups in SBR / CMC. Furthermore, the interaction between negative electrode materials, especially silicon-carbon negative electrodes, is relatively weak. Therefore, the overall battery performance, particularly low-temperature performance, is increasingly unable to meet application requirements. Polyacrylic acid binders, due to the high content of polar functional groups in the polymer, exhibit complexation and decomplexation interactions between these polar functional groups and lithium ions during charge and discharge, which can promote lithium-ion conduction and reduce battery internal resistance.

[0005] In addition, polyacrylic acid binders can form hydrogen bonds with the silicon anode surface, improving the dispersion and adhesion of the anode material, thereby suppressing the volume expansion of the anode active material during charge and discharge, improving the performance of the SEI film, and preventing the decomposition of the electrolyte during electrochemical cycling.

[0006] Currently, the PAA used in the industry is mainly water-based. To improve its ability to suppress volume expansion, PAA generally has a large molecular weight, resulting in high product viscosity and generally low solid content, which greatly increases transportation costs and usage efficiency. Meanwhile, with the development of dry electrode technology, the demand for powdered PAA is further increasing. To achieve the preparation of powdered PAA, researchers have considered using a solvent precipitation method. CN 117720869 A uses a method of precipitation polymerization followed by neutralization to prepare powder. The problem with this method is that water and solvent are miscible, affecting subsequent water and solvent separation, making solvent recycling impossible, and generating a large amount of waste. To solve these problems, this invention controls the neutralization degree of the dispersant and monomer to obtain a solid-liquid separated and incompatible product in one step. Powdered PAA can be obtained through simple filtration and drying, offering advantages such as low energy consumption and simple preparation method. Summary of the Invention

[0007] One objective of this invention is to provide a method for preparing a powder battery binder. The binder is pre-neutralized before polymerization, prepared via reverse suspension polymerization, and post-crosslinking modification using excess carboxyl monomers. The resulting binder exhibits ultra-high molecular weight and excellent adhesion.

[0008] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0009] On one hand, the present invention provides a method for preparing a powder battery binder, the method comprising the following steps:

[0010] S1: The aqueous phase mixture and the oil phase solution are mixed and then subjected to reverse suspension polymerization to obtain a suspension;

[0011] S2: The suspension is subjected to post-crosslinking treatment to obtain a modified suspension;

[0012] S3: Remove the residual oil phase and water from the modified suspension, and then dry it to obtain the powder battery binder.

[0013] The aqueous phase mixture in S1 contains pre-neutralized carboxyl-containing monomers, acrylamide, and acrylonitrile;

[0014] The oil phase solution in S1 contains a dispersant and a solvent that is immiscible with water. The dispersant includes a reactive dispersant. The solubility of the reactive dispersant in water is denoted as S, based on the saturated solubility in 100g of water at 25°C. The reactive dispersant is used to pre-neutralize the carboxyl monomers in the aqueous mixture, and the degree of neutralization N and the solubility S satisfy the following formula:

[0015] (1 / (40S)+0.25)*100%≤N≤(1 / (5S)+0.25)*100%; Preferably (1 / (30S)+0.25)

[0016] *100%≤N≤(1 / (10S)+0.25)*100%.

[0017] The term "included" in this invention means that its content is ≥20%, or ≥50%, or ≥80%, or ≥90%, or equal to 100%.

[0018] In this invention, the carboxyl-containing monomer is selected from one or more of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid and maleic acid, preferably acrylic acid and methacrylic acid.

[0019] In this invention, the solvent in the oil phase solution that is immiscible with water is a petroleum hydrocarbon solvent, such as one or more of aliphatic hydrocarbons, alicyclic hydrocarbons, or aromatic hydrocarbons; preferably, the aliphatic hydrocarbon is one or more of n-pentane, n-hexane, n-heptane, or petroleum ether, the alicyclic hydrocarbon is one or more of cyclopentane, methylcyclopentane, cyclohexane, or methylcyclohexane, and the aromatic hydrocarbon is one or more of benzene, toluene, or xylene.

[0020] In this invention, the reactive dispersant is an acrylamide-modified dispersant, such as one or more of acrylamide-modified sorbitan fatty acid esters (Span 20, Span 60, Span 80, etc.), acrylamide-modified sucrose fatty acid esters (S-370, S-570, S-970, etc.), and acrylamide-modified carboxymethyl cellulose.

[0021] The acrylamide-modified dispersant is a prior art modified dispersant, such as those described in the following references:

[0022] 1. Chen Zhengguo et al., Synthesis and Properties of Acrylate-Acylated Span 60, Daily Chemical Industry, 1998.

[0023] 2. Wang Jinghui et al., Preparation of polymeric emulsifiers by esterification reaction of Span 80 with acrylic acid, Fine Chemicals, 2007.

[0024] 3. Peng Shunjin et al., Preparation of oil-soluble nonionic polymerizable surfactant ASMO, Fine Petrochemicals, 2000.

[0025] The aforementioned documents are cited in this application as prior art.

[0026] The acrylamide-modified dispersant has the following general structural formula:

[0027]

[0028] Preferably, the amount of the reactive dispersant is 0.05- of the mass of the monomer before neutralization in the aqueous mixture during step S1.

[0029] 5%, more preferably 0.5-3%, for example, 1.25%, 1.5%, 2%, 2.5%.

[0030] In this invention, in step S1, the mass ratio of the petroleum hydrocarbon solvent in the oil phase solution to the aqueous phase mixture is 0.1-10:1, preferably 1-5:1, for example, 1.5:1, 2.5:1.

[0031] In this invention, the amount of carboxyl-containing monomers added accounts for 20-40 wt% of the total amount of monomers, the amount of acrylamide added accounts for 10-40 wt% of the total amount of monomers, and the amount of acrylonitrile added accounts for 40-50 wt% of the total amount of monomers.

[0032] Optionally, the aqueous mixture further comprises a crosslinking agent; preferably, the crosslinking agent is a small molecule compound containing two or more terminal double bonds, preferably one or more of divinylbenzene, allyl methacrylate, diallyl phthalate, pentaerythritol triallyl ether, ethylene glycol dimethacrylate, and N,N-methylenebisacrylamide; preferably, the amount of crosslinking agent added is 0-0.1 wt% of the unneutralized monomer, based on the amount of carboxyl-containing monomer.

[0033] In one embodiment of the present invention, the aqueous mixture in S1 further comprises an initiator, which is a water-soluble thermal initiator and / or a redox initiator. Preferably, the initiator is one or more of ammonium sulfate, sodium persulfate, potassium persulfate, tert-butyl hydroperoxide, hydrogen peroxide, isoascorbic acid, sodium metabisulfite, and sodium bisulfite.

[0034] In one embodiment of the present invention, a neutralizing agent is added to the carboxyl-containing monomer in S1 for pre-neutralization; preferably, the neutralizing agent is an inorganic alkali metal hydroxide, preferably one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate.

[0035] In one embodiment of the present invention, the post-crosslinking agent in S2 is a polyglycidyl ether, selected from one or more of ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and allyl glycidyl ether. Calculated based on carboxyl-containing monomers, the amount of the post-crosslinking agent added is 0.01-1 wt% of the unneutralized monomer, preferably 0.1-0.8 wt%, such as 0.3 wt% or 0.5 wt%.

[0036] In one embodiment of the present invention, in step S3, the solvent and water form an azeotrope, the removal temperature is 80-150°C, such as 90°C, 110°C, or 140°C, and the amount of water removed is 50-95% of the amount of water added; the drying is carried out by either forced air drying or fluidized bed drying, the drying temperature is 80-150°C, and the time is 0.5-2 hours.

[0037] Another object of the present invention is to provide a powder battery binder.

[0038] Another object of the present invention is to provide a use of a powder battery binder.

[0039] The use of a powder battery binder, wherein the binder is a binder prepared by the above-described preparation method, or is a binder prepared by the above-described method, and the powder battery binder is used for the positive and negative electrodes of a lithium-ion battery.

[0040] Another object of the present invention is to provide positive and negative electrodes for a lithium-ion battery, which include a powder battery binder.

[0041] The negative electrode is artificial graphite, natural graphite, hard carbon, or silicon carbide, and the positive electrode is ternary lithium, lithium cobalt oxide, lithium iron phosphate, or lithium manganese oxide.

[0042] Compared with the prior art, the present invention has the following beneficial effects:

[0043] The powder battery binder of the present invention uses a reverse-phase suspension process to effectively improve the electrochemical performance of lithium-ion batteries by providing ion transport channels through pre-neutralization. The degree of pre-neutralization is determined according to the solubility of the dispersant in water. When the solubility of the dispersant in water is high, the degree of neutralization needs to be appropriately reduced to form effectively encapsulated microspheres and a good oil-water interface. When the solubility of the dispersant in water is low, the degree of neutralization needs to be appropriately increased to allow the dispersant to be penetrated and encapsulated by strong charge repulsion, avoiding the undesirable situation of oil phase polymerization.

[0044] By using reserved carboxyl groups for post-crosslinking with polyglycidyl ethers, the binder in the dry electrode can be made fibrillated to form a network structure, which can improve the coverage and peeling force of the electrode active material and reduce the internal resistance of the battery. Detailed Implementation

[0045] The present invention will be further illustrated by specific embodiments below. These specific embodiments are merely detailed descriptions of the present invention and are not intended to limit the scope of the present invention.

[0046] The synthesis method of the reactive dispersant involved in the embodiments of the present invention is referenced in the following literature:

[0047] 1. Chen Zhengguo et al., Synthesis and Properties of Acrylate-Acylated Span 60, Daily Chemical Industry, 1998.

[0048] 2. Wang Jinghui et al., Preparation of polymeric emulsifiers by esterification reaction of Span 80 with acrylic acid, Fine Chemicals, 2007.

[0049] 3. Peng Shunjin et al., Preparation of oil-soluble nonionic polymerizable surfactant ASMO, Fine Petrochemicals, 2000.

[0050] The preparation method for acrylated sucrose fatty acid ester (S-370, solubility 0.4 g / 100 g water) is as follows:

[0051] 250g of weighed sucrose fatty acid ester, 14.4g of acrylic acid, 1.3g of p-toluenesulfonic acid (catalyst), and 1.3g of hydroquinone (polymerization inhibitor) were added to a four-necked flask containing 300mL of n-heptane (solvent). The mixture was stirred and refluxed at 108℃ for 20 hours. At this point, the amount of water exiting the separator was approximately 2.8g, and the calculated esterification rate was approximately 80%. The mixture was then filtered while hot, and the filtrate was washed with 0.1% NaOH until the pH of the aqueous phase was approximately 6. It was then washed with pure water until the pH was approximately 7. The aqueous phase was separated, and the oil phase was distilled under reduced pressure to remove the solvent, yielding the crude product. The crude product was purified with ethyl acetate and dried under vacuum to obtain the refined product.

[0052] The preparation method for acrylated sodium carboxymethyl cellulose (CMC1) (solubility 2 g / 100 g water) is as follows:

[0053] 100g of sodium carboxymethyl cellulose (brand name MAC500LC, Nippon Paper), 14.4g of acrylic acid, 1.3g of p-toluenesulfonic acid (catalyst), and 1.3g of hydroquinone (polymerization inhibitor) were weighed and added to a four-necked flask containing 150mL of toluene (solvent). The mixture was stirred and refluxed at 118°C for 15 hours. At this point, the amount of water exiting the separator was approximately 3.0g, and the calculated esterification rate was approximately 83%. The mixture was then filtered while hot, and the filtrate was washed with 0.1% NaOH until the pH of the aqueous phase was approximately 6. It was then washed with pure water until the pH was approximately 7. The aqueous phase was separated, and the oil phase was distilled under reduced pressure to remove the solvent, yielding the crude product. The crude product was purified with ethyl acetate and dried under vacuum to obtain the refined product.

[0054] The preparation method for acrylated sodium carboxymethyl cellulose (CMC2) (solubility 7 g / 100 g water) is as follows:

[0055] 80g of weighed sodium carboxymethyl cellulose (brand name BH2000, Changshu Weiyi), 14.4g of acrylic acid, 1.3g of p-toluenesulfonic acid (catalyst), and 1.3g of hydroquinone (polymerization inhibitor) were added to a four-necked flask containing 150mL of toluene (solvent). The mixture was stirred and refluxed at 118℃ for 15 hours. At this point, the amount of water output from the separator was approximately 3.0g, and the calculated esterification rate was approximately 83%. The mixture was then filtered while hot, and the filtrate was washed with 0.1% NaOH until the pH of the aqueous phase was approximately 6. It was then washed with pure water until the pH was approximately 7. The aqueous phase was separated, and the oil phase was distilled under reduced pressure to remove the solvent, yielding the crude product. The crude product was purified with ethyl acetate and dried under vacuum to obtain the refined product.

[0056] The preparation method for acrylated sodium carboxymethyl cellulose (CMC3) (solubility 7 g / 100 g water) is as follows:

[0057] 92g of weighed sodium carboxymethyl cellulose (MAC350, Nippon Paper), 14.4g of acrylic acid, 1.3g of p-toluenesulfonic acid (catalyst), and 1.3g of hydroquinone (polymerization inhibitor) were added to a four-necked flask containing 150mL of toluene (solvent). The mixture was stirred and refluxed at 118°C for 15 hours. At this point, the amount of water exiting the separator was approximately 3.0g, and the calculated esterification rate was approximately 83%. The mixture was then filtered while hot, and the filtrate was washed with 0.1% NaOH until the pH of the aqueous phase was approximately 6. It was then washed with pure water until the pH was approximately 7. The aqueous phase was separated, and the oil phase was distilled under reduced pressure to remove the solvent, yielding the crude product. The crude product was purified with ethyl acetate and dried under vacuum to obtain the refined product.

[0058] The preparation method for acrylated sorbitan fatty acid ester (Span 60, solubility 0.2 g / 100 g water) is as follows:

[0059] 190g of weighed sorbitan fatty acid ester, 14.4g of acrylic acid, 1.3g of p-toluenesulfonic acid (catalyst), and 1.3g of hydroquinone (polymerization inhibitor) were added to a four-necked flask containing 150mL of toluene (solvent). The mixture was stirred and refluxed at 118℃ for 15 hours. At this point, the amount of water exiting the separator was approximately 3.0g, and the calculated esterification rate was approximately 83%. The mixture was then filtered while hot, and the filtrate was washed with 0.1% NaOH until the pH of the aqueous phase was approximately 6. It was then washed with pure water until the pH was approximately 7. The aqueous phase was separated, and the oil phase was distilled under reduced pressure to remove the solvent, yielding the crude product. The crude product was purified with ethyl acetate and dried under vacuum to obtain the refined product.

[0060] The preparation method for acrylated sorbitan fatty acid ester (Span 80, solubility 0.5 g / 100 g water) is as follows:

[0061] 205g of weighed sorbitan fatty acid ester, 14.4g of acrylic acid, 1.3g of p-toluenesulfonic acid (catalyst), and 1.3g of hydroquinone (polymerization inhibitor) were added to a four-necked flask containing 150mL of toluene (solvent). The mixture was stirred and refluxed at 118℃ for 15 hours. At this point, the amount of water exiting the separator was approximately 3.0g, and the calculated esterification rate was approximately 83%. The mixture was then filtered while hot, and the filtrate was washed with 0.1% NaOH until the pH of the aqueous phase was approximately 6. It was then washed with pure water until the pH was approximately 7. The aqueous phase was separated, and the oil phase was distilled under reduced pressure to remove the solvent, yielding the crude product. The crude product was purified with ethyl acetate and dried under vacuum to obtain the refined product.

[0062] The main raw materials and their sources used in the examples and comparative examples are shown in Table 1:

[0063] Table 1. Main raw materials and sources for preparing solution-type binders

[0064] English abbreviations compound Manufacturer AA acrylic acid Wanhua Chemical Group Co., Ltd. MAA methacrylic acid Wanhua Chemical Group Co., Ltd. AN Acrylonitrile Wanhua Chemical Group Co., Ltd. AM Acrylamide Wanhua Chemical Group Co., Ltd. MBA N,N-Methylenebisacrylamide Jinan Nuoshi New Materials Co., Ltd. PEGDA 400 Polyethylene glycol 400 diacrylate Sinopharm Group SPS Sodium persulfate Unite Initiator Hefei Co., Ltd. KPS Potassium persulfate Unite Initiator Hefei Co., Ltd. <![CDATA[Na2S2O5]]> Sodium metabisulfite Wanhua Chemical Group Co., Ltd. n-Heptane n-Heptane Sinopharm Group n-Hexane n-Hexane Sinopharm Group Ethylene glycol diglycidyl ether Ethylene glycol diglycidyl ether Anhui Hengyuan Butylene glycol diglycidyl ether Butylene glycol diglycidyl ether Anhui Hengyuan

[0065] Unless otherwise specified, all other chemical reagents used in the examples were purchased from the market and were of analytical grade.

[0066] Example 1

[0067] 500g of n-heptane was added to a 2L four-necked detachable flask equipped with a stirrer, reflux condenser, thermometer, and nitrogen inlet pipe. 0.92g of acrylated Span 60 (a reactive dispersant, prepared according to reference 1) was added, the mixture was heated to 80°C and stirred at 400rpm to dissolve and disperse it evenly, and then cooled to 50°C. This is the oil phase solution.

[0068] Add 124g of acrylic acid to a 1L conical flask. Add 140g of a 32% sodium hydroxide aqueous solution dropwise to the flask while cooling to below 45°C. Then add 50g of acrylamide, 140g of acrylonitrile, 0.368g of potassium persulfate, 0.184g of polyethylene glycol 400 diacrylate (PEGDA400), and 172g of deionized water. Stir and mix thoroughly to form an aqueous phase mixture.

[0069] Half of the above aqueous mixture was added to a four-necked flask, and nitrogen gas was introduced while stirring at 400 rpm for 30 minutes. Then the temperature was raised to 80°C and the polymerization reaction was carried out for 1 hour to obtain a polymer suspension.

[0070] The temperature was raised to 95℃, and 0.2g of ethylene glycol diglycidyl ether was added to the polymerization suspension. The reaction was continued for 2 hours to obtain a modified suspension. The system was filtered and centrifuged to remove residual n-heptane and water. Finally, it was dried at 150℃ for 40 minutes to obtain the powder battery binder.

[0071] Example 2

[0072] The amounts of each raw material used in Examples 2-6 and Comparative Examples 1-4 are shown in Table 2.

[0073] Table 2 Usage of each raw material

[0074]

[0075] Table 3. Neutralization and dispersant solubility of the examples and comparative examples.

[0076] Group Neutralization degree N Solubility S Does it meet the limiting conditions? Example 1 65 0.2 yes Example 2 30 2 yes Example 3 25 7 yes Example 4 49 0.4 yes Example 5 42 0.5 yes Example 6 28 3 yes Comparative Example 1 0 0.2 no Comparative Example 2 83 0.2 no Comparative Example 3 56 0.2 yes

[0077] Test method:

[0078] The solubility test method is as follows: Weigh 100g of deionized water at a constant temperature of 25℃, and continuously add reactive dispersant to the water while stirring. As the amount added increases, the viscosity of the aqueous solution containing the reactive dispersant begins to increase until, after thorough stirring (4h), particulate aggregates of the reactive dispersant that cannot be dispersed appear in the aqueous solution. At this point, the saturation solubility of the reactive dispersant is reached, which is the solubility of the reactive dispersant at 25℃.

[0079] The powder battery binder prepared in the examples and comparative examples was applied to the preparation of the negative electrode sheet of a lithium-ion battery, and the steps are as follows:

[0080] At room temperature, 1 part of conductive carbon black sp and 97.2 parts of negative electrode active material (graphite) were added to a mixing tank and mixed. Then, 1.8 parts of powder battery binder were added. External high shear force was applied to the dry mixture to make the battery binder fibrillate and bond the electrode film powder. Finally, the mixture was extruded to form a self-supporting film.

[0081] The prepared negative electrode sheets were evaluated for peel strength and electrochemical performance.

[0082] Peel strength evaluation: Tested using a specialized adhesive strength tester. The peel strength test method conforms to the American Society for Testing and Materials (ASTM) standard D3330. The instrument used is a Kejian tensile testing machine, specifically as follows: The negative electrode sheet is cut into 150mm long and 15mm wide sheets along the rolling direction. A 100mm long and 15mm wide strip of 3M double-sided tape is applied to a smooth stainless steel plate. The electrode sheet is then flatly attached to the double-sided tape and rolled back and forth 10 times with a 2kg rubber roller. The stainless steel plate is then fixed to the tensile testing machine. The electrode sheet not attached to the tape is clamped in reverse on the tensile testing machine probe. The tensile testing machine base pulls the electrode sheet at a speed of 5cm / min, and the sensor measures the peel force during this process. The average value of 5 parallel samples in each group is the final peel strength.

[0083] Peeling force = Computer reading / 0.015, unit is N / m.

[0084] Electrochemical performance evaluation: The prepared negative electrode sheet and the positive electrode sheet with lithium iron phosphate as the positive electrode material are prepared and assembled into an aluminum-plastic soft package according to the lithium-ion battery production process familiar to technicians in this industry, and then electrochemical performance is tested.

[0085] Specifically as follows:

[0086] Determining the capacity retention rate after 1000 cycles: At 25℃ and a voltage range of 3.5V, the charge-discharge cycle was performed with 0.5C charging and 1.0C discharging. The capacity retention rate after 1000 cycles was tested using the constant current method. Capacity retention rate = discharge capacity of the 1000th cycle / discharge capacity of the 1st cycle.

[0087] Membrane resistance testing method: Cut a 20cm long negative electrode after rolling. Randomly select 10 points on the coated area of ​​the electrode and measure the resistance at each point using a four-probe membrane resistance meter. The average of the 10 values ​​is the final membrane resistance value. Instrument: ACCFILM four-probe membrane resistance meter TT-ACCF-G2A.

[0088] Table 5 Electrochemical performance data

[0089]

[0090]

[0091] The performance results in the table show that Examples 1-6 all exhibit high peel strength, low membrane resistance, good fibrous formation properties, and excellent cycle capacity retention. In Control Group 1, the lack of pre-neutralization resulted in insufficient electrostatic repulsion, leading to decreased ion conductivity and a significant increase in membrane resistance. Control Group 2, after neutralization, suffered from insufficient post-crosslinking efficiency, preventing fibrous formation. Control Group 3 demonstrates that even without a post-crosslinking agent, fibrous formation is impossible, further highlighting the importance and necessity of post-crosslinking.

[0092] The above description is merely a specific depiction of preferred embodiments of the present invention and is not intended to limit the scope of protection of the present invention. It should be noted that those skilled in the art can make several improvements and additions based on the technical solutions of the present invention, and all such improvements and additions should fall within the scope of protection of the present invention.

Claims

1. A method for preparing a powder battery binder, the method comprising the following steps: S1: The aqueous phase mixture and the oil phase solution are mixed and then subjected to reverse suspension polymerization to obtain a suspension; S2: The suspension is subjected to post-crosslinking treatment to obtain a modified suspension; the post-crosslinking agent is a polyglycidyl ether, selected from one or more of ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and allyl glycidyl ether. S3: Remove the residual oil phase and water from the modified suspension, and then dry it to obtain the powder battery binder; The aqueous phase mixture in S1 contains pre-neutralized carboxyl-containing monomers, acrylamide, and acrylonitrile; The oil phase solution in S1 contains a dispersant and a solvent that is immiscible with water. The dispersant includes a reactive dispersant. The solubility of the reactive dispersant in water is denoted as S, based on the saturated solubility in 100g of water at 25°C. The reactive dispersant is used to pre-neutralize the carboxyl monomers in the aqueous mixture, and the degree of neutralization N and the solubility S satisfy the following formula: (1 / (30S)+0.25)*100%≤N≤(1 / (10S)+0.25)*100%; The reactive dispersant is an acrylamide-modified dispersant; the amount of the post-crosslinking agent added is 0.01-1 wt% of the unneutralized monomer, calculated based on the carboxyl-containing monomer.

2. The preparation method according to claim 1, characterized in that, The carboxyl-containing monomer is selected from one or more of acrylic acid, methacrylic acid, itaconic acid, crotonic acid, fumaric acid, and maleic acid.

3. The preparation method according to claim 1, characterized in that, The solvent in the oil phase solution that is immiscible with water is a petroleum hydrocarbon solvent.

4. The preparation method according to claim 3, characterized in that, The petroleum hydrocarbon solvent is selected from one or more of aliphatic hydrocarbons, alicyclic hydrocarbons, or aromatic hydrocarbons.

5. The preparation method according to claim 4, characterized in that, The aliphatic hydrocarbon is one or more of n-pentane, n-hexane, n-heptane or petroleum ether; the alicyclic hydrocarbon is one or more of cyclopentane, methylcyclopentane, cyclohexane or methylcyclohexane; and the aromatic hydrocarbon is one or more of benzene, toluene or xylene.

6. The preparation method according to any one of claims 1-4, characterized in that, The reactive dispersant is one or more of acrylated sorbitan fatty acid ester, acrylated sucrose fatty acid ester, and acrylated carboxymethyl cellulose; the sorbitan fatty acid ester is selected from Span20, Span60, and Span80; the acrylated sucrose fatty acid ester is selected from S-370, S-570, and S-970.

7. The preparation method according to claim 6, characterized in that, The reactive dispersant is an acrylamide-modified dispersant having the following general structural formula: 。 8. The preparation method according to any one of claims 1-4, characterized in that, The amount of the reactive dispersant is 0.05-5% of the mass of the monomer before neutralization in the aqueous phase mixture in step S1; and / or, the mass ratio of the petroleum hydrocarbon solvent in the oil phase solution to the aqueous phase mixture is 0.1-10:1; and / or, the amount of carboxyl-containing monomer added accounts for 20-40 wt% of the total monomer, the amount of acrylamide added accounts for 10-40 wt% of the total monomer, and the amount of acrylonitrile added accounts for 40-50 wt% of the total monomer.

9. The preparation method according to any one of claims 1-4, characterized in that, The amount of the reactive dispersant is 0.5-3% of the mass of the monomer before neutralization in the aqueous phase mixture in step S1; and / or, the mass ratio of the petroleum hydrocarbon solvent in the oil phase solution to the aqueous phase mixture is 1-5:

1.

10. The preparation method according to any one of claims 1-4, characterized in that, The aqueous mixture further comprises a crosslinking agent, which is a small molecule compound containing two or more terminal double bonds. The amount of crosslinking agent added is 0-0.1 wt% of the unneutralized monomer, based on the amount of carboxyl monomer.

11. The preparation method according to claim 10, characterized in that, The crosslinking agent is one or more of divinylbenzene, allyl methacrylate, diallyl phthalate, pentaerythritol triallyl ether, ethylene glycol dimethacrylate, and N,N-methylenebisacrylamide.

12. The preparation method according to any one of claims 1-4, characterized in that, The aqueous mixture described in S1 also contains an initiator, which is a water-soluble thermal initiator and / or a redox initiator.

13. The preparation method according to claim 12, characterized in that, The initiator is one or more of the following: ammonium sulfate, sodium persulfate, potassium persulfate, tert-butyl hydroperoxide, hydrogen peroxide, isoascorbic acid, sodium metabisulfite, and sodium bisulfite.

14. The preparation method according to any one of claims 1-4, characterized in that, S1 The carboxyl-containing monomer is pre-neutralized by adding a neutralizing agent, wherein the neutralizing agent is an inorganic alkali metal hydroxide.

15. The preparation method according to any one of claims 1-4, characterized in that, S1 The carboxyl-containing monomer is pre-neutralized by adding a neutralizing agent, wherein the neutralizing agent is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, lithium carbonate, sodium carbonate, and potassium carbonate; and / or, based on the carboxyl-containing monomer, the amount of the post-crosslinking agent added is 0.1-0.8 wt% of the unneutralized monomer.

16. A powder battery binder prepared by the preparation method according to any one of claims 1-15.

17. The use of the powder battery binder prepared by the preparation method according to any one of claims 1-15 or the powder battery binder according to claim 16 as a positive and negative electrode binder for lithium-ion batteries.

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