Water-soluble granular binder, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of lithium-ion battery binders, and relates to a water-soluble granular binder, and a preparation method therefor and a use thereof. The technical problem to be solved by the present invention is to provide a water-soluble granular binder. The binder comprises organic polymer particles, and the morphology of the organic polymer particles is secondary particles formed by aggregating primary particles. Polymerization monomers of the organic polymer particles comprise a hydrophilic monomer and a lipophilic monomer. The hydrophilic monomer includes an unsaturated acid monomer. The weight percentage ratio of the hydrophilic monomer to the lipophilic monomer is 30-70%:70-30%. The water-soluble granular binder of the present invention is particles having a specific morphology, is convenient for storage and transportation, and can be quickly dissolved in water. The binder is applied to preparation of a negative electrode slurry and can improve the stability of the slurry. The binder exhibits good binding performance, can increase the solid content of a slurry in an existing silicon-carbon slurry formulation, improve production efficiency, and can effectively suppress volume expansion and suppress full-charge rebound of an electrode sheet.

Description

Water-soluble particulate binders, their preparation methods and applications

[0001] Cross-reference to related applications

[0002] This application claims the benefit and priority of Chinese patent application CN2025103731187, filed on March 27, 2025, which is incorporated herein by reference and for all other purposes. Technical Field

[0003] This invention relates to water-soluble particulate binders, their preparation methods, and applications, belonging to the field of lithium-ion battery binder technology. Background Technology

[0004] Silicon, as one of the next-generation anode materials for lithium-ion batteries, boasts advantages such as high specific capacity, low cost, and abundant natural reserves. However, the volume expansion (approximately 300%) of silicon during charge-discharge and storage hinders its commercialization and widespread application. Unlike traditional carbon materials, the massive volume expansion of silicon easily causes the active material particles to break down, leading to electrical network bridging, affecting battery cycle life, increasing internal resistance, and ultimately causing rapid battery failure. To constrain the excessive expansion of silicon, high-modulus binders are typically used to limit this volume expansion.

[0005] PAA polymers are widely used as binders in silicon anodes. Their molecular chains contain numerous carboxyl groups, which enable them to exert strong interactions with the silicon-based substrate during electrode fabrication processes such as coating and baking, thus providing robust adhesion. Therefore, PAA binders have achieved good electrochemical performance in silicon anodes.

[0006] Patent application number 202010542779.5 discloses a battery adhesive, a lithium-ion battery negative electrode sheet, and a lithium-ion battery. This adhesive exhibits higher adhesion strength and can increase the proportion of active material (negative electrode material), thereby increasing the battery's energy density. However, this solid adhesive is prone to agglomeration and stickiness, affecting later use, and the solid needs to be neutralized before it can dissolve in water, increasing later application costs. Furthermore, using the neutralized adhesive as a product would increase transportation costs.

[0007] Summary of the Invention

[0008] To address the above deficiencies, the technical problem solved by this invention is to provide a water-soluble particulate binder.

[0009] The present invention relates to a water-soluble particulate binder comprising organic polymer particles, wherein the organic polymer particles are formed by the aggregation of primary particles into secondary particles, and the polymer monomers of the organic polymer particles include hydrophilic monomers and lipophilic monomers, wherein the hydrophilic monomers include monomers containing double bonds and acids, and the weight percentage of the hydrophilic monomers and lipophilic monomers is 30-70% : 70-30%.

[0010] In one embodiment of the present invention, the particle size D50 of the primary particles is 1 μm to 1000 μm, and the particle size D50 of the secondary particles is 100 μm to 2000 μm.

[0011] In one embodiment of the present invention, the hydrophilic monomer further includes at least one of a double-bonded salt monomer and a double-bonded amide monomer; the lipophilic monomer includes at least one of a double-bonded benzene ring monomer, a double-bonded nitrile monomer, and a double-bonded ester monomer.

[0012] In one embodiment of the present invention, the monomers containing double bonds include at least one of (meth)acrylic acid, (meth)propylene sulfonic acid, maleic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyloxyhydroxypropyl sulfonic acid, β-acryloyloxypropionic acid, and 2-fluoroacrylic acid; the monomers containing double bonds include at least one of (meth)acrylate, (meth)propylene sulfonate, maleate, itaconic acid, allyloxyhydroxypropyl sulfonate, β-acryloyloxypropionic acid, and 2-fluoroacrylate; wherein the salt is a lithium salt, sodium salt, or potassium salt; the monomers containing double bonds include acrylamide, methacrylamide, N,N-diethylacrylamide, N,N-diethylmethylacrylamide, N-ethylacrylamide, N-ethylmethylacrylamide, N,N-dimethylacrylamide, N, At least one of N-dimethylmethacrylamide, N-methacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, and N-isopropylmethacrylamide; monomers containing a double-bonded benzene ring, including at least one of styrene, methylstyrene, tetrapropylenebenzene, methyl p-vinylphenyl ether, divinylbenzene, stilbene, tristyrene, and tetrastyrene; monomers containing a double-bonded nitrile, including at least one of acrylonitrile, methacrylonitrile, isobutylenenitrile, 2-pentenenitrile, 5-hexenenitrile, and 6-heptenenitrile; monomers containing a double-bonded ester, including methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, and methyl methacrylate. Hydroxybutyl acrylate, butyl acrylate, butyl methacrylate, n-octyl acrylate, isooctyl acrylate, isooctyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, isobornyl acrylate, isobornyl methacrylate, propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, phenyl methacrylate, hexadecyl acrylate, sulfonyl acrylate, sulfonyl methacrylate, glycidyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, vinyl methacrylate, benzyl methacrylate, phenyl methacrylate, hexadecyl methacrylate.

[0013] In one embodiment of the present invention, the hydrophilic monomers contain 1-70 parts by weight of double-bonded acid monomers, 0-70 parts by weight of double-bonded salt monomers, and 0-70 parts by weight of double-bonded amide monomers; the lipophilic monomers contain 0-70 parts by weight of double-bonded benzene ring monomers, 0-70 parts by weight of double-bonded nitrile monomers, and 0-70 parts by weight of double-bonded ester monomers, wherein the number of monomers containing double-bonded benzene ring monomers, double-bonded nitrile monomers, and double-bonded ester monomers is not simultaneously 0.

[0014] In one embodiment of the present invention, the weight-average molecular weight of the organic polymer particles is 300,000 to 3,000,000.

[0015] In one embodiment of the present invention, the organic polymer particles account for more than 95% by weight of the water-soluble particulate binder.

[0016] The present invention also provides a method for preparing the water-soluble particulate binder described herein.

[0017] The method for preparing the water-soluble particulate binder of the present invention includes the following steps:

[0018] 1) Copolymerization: Under a protective atmosphere, the monomer is added to water, an initiator is added to initiate the polymerization reaction, a solid-liquid mixture is obtained, and then the precipitate is collected;

[0019] 2) Neutralization: Add the precipitate obtained in step 1) to the mixed solvent, stir, and neutralize until the pH of the supernatant is 6.5-9. Take out the polymer, place it in organic solvent A and stir for at least 60 minutes. Take out the polymer and dry it to obtain the water-soluble particulate binder.

[0020] In one embodiment of the present invention, in step 2), the mixed solvent is organic solvent B and water, and the mass ratio of organic solvent B to water is 30:70 to 95:5; preferably, the mass ratio of organic solvent B to water is 70:30.

[0021] In one embodiment of the present invention, the organic solvent A is at least one selected from N-methylpyrrolidone, isopropanol, ethanol, methanol, and acetonitrile, and the organic solvent B is at least one selected from N-methylpyrrolidone, isopropanol, ethanol, methanol, and acetonitrile.

[0022] This invention also provides the application of the water-soluble particulate binder described herein in the preparation of lithium-ion battery anode slurry.

[0023] This invention relates to a water-soluble particulate binder that can be used in lithium-ion battery anode slurries to improve the solid content and stability of the slurry, facilitating subsequent processing. Simultaneously, the binder exhibits excellent adhesion properties, enhancing the peel strength of the electrode and effectively suppressing the expansion of the silicon-carbon anode electrode.

[0024] In one embodiment of the present invention, the negative electrode slurry is a silicon-carbon negative electrode slurry.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] This invention relates to a water-soluble particulate binder, which consists of particles with a specific morphology, facilitating storage and transportation and allowing for rapid dissolution in water. This binder is used in the preparation of negative electrode slurries, improving slurry stability. It exhibits excellent adhesion properties, enhancing the peel strength between the negative electrode material and the electrode sheet. The adhesive strength of this binder is approximately 40-50% higher than that of solution-based binders. Existing silicon-carbon slurry formulations often include carbon nanotube dispersions, which typically have low solids content, while commercially available solution-based PAA binders contain 6-12%. Therefore, powder-based PAA binders can increase the slurry's solids content, improve production efficiency, and effectively suppress volume expansion and electrode rebound when fully charged. Attached Figure Description

[0027] Figure 1 is a SEM image of the product of Embodiment 1 of the present invention.

[0028] Figure 2 is a SEM image of the product of Comparative Example 1 of the present invention.

[0029] Figure 3 is a SEM image of the product of Comparative Example 2 of the present invention. Detailed Implementation

[0030] The present invention relates to a water-soluble particulate binder comprising organic polymer particles, wherein the organic polymer particles are formed by the aggregation of primary particles into secondary particles, and the polymer monomers of the organic polymer particles include hydrophilic monomers and lipophilic monomers, wherein the hydrophilic monomers include monomers containing double bonds and acids, and the weight percentage of the hydrophilic monomers and lipophilic monomers is 30-70% : 70-30%.

[0031] In one embodiment of the present invention, the particle size D50 of the primary particles is 1 μm to 1000 μm, and the particle size D50 of the secondary particles is 100 μm to 2000 μm.

[0032] In one embodiment of the present invention, the hydrophilic monomer further includes at least one of a double-bonded salt monomer and a double-bonded amide monomer; the lipophilic monomer includes at least one of a double-bonded benzene ring monomer, a double-bonded nitrile monomer, and a double-bonded ester monomer.

[0033] In one embodiment of the present invention, the double-bonded acid monomer includes at least one of (meth)acrylic acid, (meth)propenesulfonic acid, maleic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyloxyhydroxypropylsulfonic acid, β-acryloyloxypropionic acid, and 2-fluoroacrylic acid.

[0034] The double-bonded salt monomers include at least one of (meth)acrylate, (meth)propene sulfonate, maleate, itaconic acid, allyloxyhydroxypropyl sulfonate, β-acryloyloxypropionate, and 2-fluoroacrylate; wherein the salt is a lithium salt, sodium salt, or potassium salt.

[0035] The amide monomers containing double bonds include at least one of acrylamide, methacrylamide, N,N-diethylacrylamide, N,N-diethylmethylacrylamide, N-ethylacrylamide, N-ethylmethylacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethylacrylamide, N-methylacrylamide, N-methylmethylacrylamide, N-isopropylacrylamide, and N-isopropylmethylacrylamide.

[0036] Monomers containing double-bonded benzene rings include at least one of styrene, methylstyrene, tetrapropylenebenzene, methyl p-vinylphenyl ether, divinylbenzene, stilbene, tristyrene, and tetrastyrene.

[0037] The nitrile monomers containing double bonds include at least one of acrylonitrile, methacrylonitrile, isobutylene nitrile, 2-pentene nitrile, 5-hexene nitrile, and 6-heptene nitrile.

[0038] Monomers containing double bonds include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, butyl acrylate, butyl methacrylate, n-octyl acrylate, isooctyl acrylate, isooctyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, isobornyl acrylate, isobornyl methacrylate, propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, phenyl methacrylate, hexadecyl acrylate, sulfonyl acrylate, sulfonyl methacrylate, glycidyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, vinyl methacrylate, benzyl methacrylate, phenyl methacrylate, and hexadecyl methacrylate.

[0039] In this invention, "(meth)propylene..." means "propylene..." or "methpropylene...", for example, (meth)acrylic acid means acrylic acid or methacrylic acid, and (meth)propylene sulfonic acid means propylene sulfonic acid or methpropylene sulfonic acid.

[0040] In one embodiment of the present invention, the hydrophilic monomer contains 1 to 70 parts by weight of double bond acid monomers, 0 to 70 parts by weight of double bond salt monomers, and 0 to 70 parts by weight of double bond amide monomers.

[0041] By weight, the lipophilic monomers contain 0-70 parts of double-bonded benzene ring monomers, 0-70 parts of double-bonded nitrile monomers, and 0-70 parts of double-bonded ester monomers, and the number of double-bonded benzene ring monomers, double-bonded nitrile monomers, and double-bonded ester monomers is not 0 at the same time.

[0042] In one embodiment of the present invention, the weight-average molecular weight of the organic polymer particles is 300,000 to 3,000,000.

[0043] In one embodiment of the present invention, the organic polymer particles account for more than 95% by weight of the water-soluble particulate binder.

[0044] The method for preparing the water-soluble particulate binder of the present invention includes the following steps:

[0045] 1) Copolymerization: Under a protective atmosphere, the monomer is added to water, and an initiator is added to initiate the polymerization reaction, resulting in a solid-liquid mixture. The precipitate is then collected.

[0046] 2) Neutralization: Add the precipitate obtained in step 1) to the mixed solvent, stir, and neutralize until the pH of the supernatant is 6.5-9. Take out the polymer, place it in organic solvent A and stir for at least 60 minutes. Take out the polymer and dry it to obtain the water-soluble particulate binder.

[0047] The preparation method of this invention uses water as a solvent for polymerization reaction, followed by neutralization in a mixed solvent, to obtain binder particles with specific morphologies. This allows for flexible control of molecular weight and rapid dissolution, thereby improving the performance of the binder.

[0048] Step 1) is a copolymerization reaction. Water is used as the solvent, and the monomers copolymerize under the action of an initiator to obtain a copolymer precipitate. This reaction can use any type of initiator commonly used in the art, as long as it can initiate the polymerization reaction. The reaction temperature and time are related to the selected initiator and the type of monomer; those skilled in the art can make conventional selections according to actual needs.

[0049] Step 2) is primarily a neutralization reaction, neutralizing all or part of the carboxylic acid or sulfonic acid in the polymer into a salt to increase its hydrophilicity, allowing the resulting product to be easily dispersed in water. Neutralization in a mixed solvent can give the polymer a specific morphology. In one embodiment of the invention, in step 2), the mixed solvent is organic solvent B and water, and the mass ratio of organic solvent B to water is 30:70 to 95:5; preferably, the mass ratio of organic solvent B to water is 70:30.

[0050] After neutralization, the polymer is removed and placed in organic solvent A, which allows the polymer particles to shrink fully, making the precipitate loose and non-sticky.

[0051] In one embodiment of the present invention, the organic solvent A is not limited to at least one of N-methylpyrrolidone, isopropanol, ethanol, methanol, and acetonitrile, and the organic solvent B is not limited to at least one of N-methylpyrrolidone, isopropanol, ethanol, methanol, and acetonitrile.

[0052] This invention relates to a water-soluble particulate binder that can be used in lithium-ion battery anode slurries to improve the solid content and stability of the slurry, facilitating subsequent processing. Simultaneously, the binder exhibits excellent adhesion properties, enhancing the peel strength of the electrode and effectively suppressing the expansion of the silicon-carbon anode electrode.

[0053] In one embodiment of the present invention, the negative electrode slurry is a silicon-carbon negative electrode slurry. The specific embodiments of the present invention will be further described below with reference to examples, but these are not intended to limit the present invention to the scope of the described embodiments.

[0054] Example 1

[0055] Add 5 parts acrylamide, 8 parts N-vinylpyrrolidone, and 566 parts distilled water to a reaction vessel, stir to dissolve, and rotate at 300 r / min. Purge with nitrogen for 30 min to remove oxygen. Heat to 70°C, then add 38 parts acrylic acid, 45 parts acrylonitrile, and 4 parts butyl acrylate, and maintain the temperature at 70°C. Then add 0.05 parts ammonium persulfate to initiate the reaction. After reacting for 9 h, remove the precipitate, filter the supernatant, and place the precipitate in a mixed solvent of N-methylpyrrolidone:water = 7:3 to neutralize the pH to 6.5–9. Then place the precipitate in ethanol, stir thoroughly to shrink, and dry to obtain a water-soluble granular adhesive.

[0056] Examples 2-9

[0057] Following the method of Example 1, some parameters were changed to obtain a water-soluble particulate binder. The changed parameters are shown in Table 1.

[0058] Table 1

[0059]

[0060]

[0061] Comparative Example 1

[0062] Add 5 parts acrylamide, 8 parts N-vinylpyrrolidone, and 566 parts distilled water to a reaction vessel, stir to dissolve, and rotate at 300 r / min; purge oxygen with nitrogen for 30 min; heat to 70℃, then add 38 parts acrylic acid, 45 parts acrylonitrile, and 4 parts butyl acrylate, and maintain the temperature at 70℃; then add 0.05 parts ammonium persulfate to initiate the reaction, and after reacting for 9 h, remove the precipitate, neutralize the pH to 6.5–9, and obtain a PAA solution.

[0063] Comparative Example 2

[0064] The PAA solution obtained in Comparative Example 1 was spray-dried to obtain binder powder.

[0065] Comparative Example 3

[0066] The PAA solution obtained in Comparative Example 1 was dried and then pulverized to obtain a granular adhesive.

[0067] Comparative Example 4

[0068] The secondary particle adhesive obtained in Example 1 was further pulverized to obtain adhesive powder.

[0069] The products prepared in Examples 1-8 and Comparative Examples 1-2 were observed using scanning electron microscopy. The SEM image of the water-soluble particulate binder prepared in Example 1 is shown in Figure 1, and the SEM images of the water-soluble particulate binders prepared in the other examples are similar to Figure 1. The SEM image of the product of Comparative Example 1 is shown in Figure 2, and the SEM image of the product of Comparative Example 2 is shown in Figure 3. It can be seen that the product of this invention consists of secondary particles formed by the aggregation of primary particles, whereas particles directly spray-dried or dried using PAA solution and then pulverized cannot form secondary particles.

[0070] Determining the particle size of the product of this invention

[0071] Particle size testing: The particle size was tested using a laser particle size analyzer (Mastersizer 3000). Analysis mode: general; Particle type: non-spherical; Opacity: 4-10%; Refractive index: 1.36; Absorption rate: 0.01; Medium: ethanol.

[0072] The results are shown in Table 2.

[0073] Table 2

[0074]

[0075] The dissolution time and molecular weight of the products in the examples were determined, and the results are shown in Table 3.

[0076] Table 3

[0077]

[0078] The solid content test method is as follows: Take 3-5 g of adhesive, spread it evenly on a tray, start the equipment, and after the weight is baked to a constant value, the equipment will stop automatically. Read the solid content value. Test parameters: 115℃, 70s automatic program, drying method moisture analyzer (LHS16-A, accuracy: 0.1g, Shanghai Tianmei Balance Instrument Co., Ltd.)

[0079] The viscosity test method is as follows: Prepare a 6% aqueous solution of adhesive, take 350g of adhesive solution with a measuring cup (about 70 mm in diameter and about 130 mm in height), keep the temperature constant to 25℃, and measure the viscosity using a viscosity tester (Brookfield DV2T).

[0080] The pH test method is as follows: Prepare a 0.6% aqueous solution of the adhesive, use a digital pH meter (Mettler S400K) with three-slope correction to measure the pH value of the sample and record the test results.

[0081] Molecular weight determination method: Gel permeation chromatography (GPC) was used. A mobile phase was prepared in a centrifuge tube. An appropriate amount of sample was dissolved in buffer solution, mixed thoroughly, and allowed to stand for at least 5 hours. An appropriate amount of supernatant was transferred to a sample vial. The program was opened, the corresponding method was selected, the flow rate was set, and the curve was monitored. Injection was initiated after the curve stabilized. After injection, the corresponding curve was selected, the data processing method was opened, and the weight-average molecular weight (Mw) and molecular weight distribution of the polymer were tested.

[0082] Method for determining dissolution time:

[0083] Dissolve the adhesive powder to prepare a 1% solids solution and record the dissolution time until the gel content is ≤5ppm.

[0084] Method for determining gel content:

[0085] 1) Weigh 495g of distilled water and place it in a vibratory mixer at 600 rpm / min;

[0086] 2) Prepare a 0.1% adhesive solution with distilled water, and weigh 5g of adhesive powder using weighing paper;

[0087] 3) Slowly add the adhesive powder to distilled water under stirring and stir at a constant speed for 1 hour for later use;

[0088] 4) Weigh the filter screen and record the weight as m1, then fold it into a funnel for later use;

[0089] 5) Pour all the adhesive solution into the filter screen, rinse the beaker three times with an appropriate amount of distilled water, and pour the washing solution into the filter screen each time.

[0090] 6) Wash the filter screen with distilled water until no glue residue remains. Drain the distilled water, then place it in a forced-air oven to bake at 110℃ for 2 hours (if there are many clumps of glue, extend the baking time until the filter screen reaches a constant weight).

[0091] 7) Weigh the dried filter screen and record the weight as m2;

[0092] 8) Calculate gel content (ppm): Gel content = (m2-m1) / 5 / 1000000.

[0093] Preparation of silicon anode paste

[0094] The slurry formulation is as follows: by weight percentage, main material (silicon-carbon composite material with a specific capacity of 750mAh·g-1) 94.45%, conductive carbon black SP 1%, CMC 0.5%, binder 2.0%, SBR 2.0%, and single-arm carbon nanotube dispersion 0.05%.

[0095] Slurry preparation process: After kneading the main material, SP and CMC with water, add binder powder, test the viscosity, add water to adjust the viscosity to the qualified level, add SBR and stir slowly, then discharge to obtain negative electrode slurry.

[0096] The parameters of the silicon anode slurry were measured, and the results are shown in Table 4.

[0097] Table 4

[0098]

[0099] It is evident that the binder of the present invention, when configured into a silicon anode slurry, can improve the solid content and static stability of the slurry.

[0100] Negative electrode performance test

[0101] The above-mentioned negative electrode slurry was prepared into a negative electrode sheet. The preparation method was as follows: the negative electrode slurry was coated onto copper foil using a small coating machine, dried in an oven tunnel, and then the electrode sheet was cut using a sheet cutter, weighed, and the double-sided surface density was controlled to be 120 g / m². 2 Then, the electrode sheets are pressed using a roller press to a compaction density of 1.55 g / cm³. 3 ,to obtain the negative electrode sheet;

[0102] Adhesion strength test method: Cut the electrode sheet into 40 mm pieces. For a 100 mm diameter electrode, adhere the coated side of the electrode tightly to a stainless steel plate with double-sided tape. Peel the electrode 20-30 mm off the stainless steel plate and secure it with tape, with the other end of the tape fixed between the upper and lower clamps. First, calibrate and zero the plate, set the test width, electrode peeling length to 50 mm, and peeling speed to 20 mm / min, then begin the test. The peel strength curve and average value will then be obtained. When processing the data, delete the start and end segments of the test to obtain the standard curve. Calculate the adhesive force using the formula: Adhesive Force = FN / 0.04, where FN is the average peel force in N, and 0.04 is the average electrode width in m.

[0103] The results are shown in Table 5.

[0104] Table 5

[0105]

[0106] It is evident that the adhesive of this invention can improve the adhesion of the electrode sheet.

[0107] Full charge rebound rate test:

[0108] 1) Preparation of the positive electrode sheet: The positive electrode active material (nickel-cobalt-manganese ternary material S85E), conductive agent (SP), and binder are combined.

[0109] The binder (polyvinylidene fluoride PVDF) was mixed at a mass ratio of 97.0:1.0:2.0 and added to NMP at a solid content of 75% to form a uniform positive electrode slurry. The negative electrode slurry was coated onto aluminum foil using a small coating machine and dried in an oven. The electrode sheets were then cut using a sheet cutter, weighed, and their areal density was calculated. Finally, the electrode sheets were rolled to the compacted density using a roller press to obtain the positive electrode sheet.

[0110] 2) Preparation of the negative electrode sheet: as described above;

[0111] 3) Separator: Porous PP polymer film;

[0112] 4) Assembly of lithium-ion batteries: The positive electrode, separator, and negative electrode are wound in sequence to obtain the battery cell; the battery cell

[0113] The lithium-ion battery is obtained by encapsulating it with an aluminum-plastic film, baking to remove water, injecting electrolyte (EC / PC / EMC=27 / 5 / 68, 1mol / L LiPF6), vacuum sealing, standing, formation, secondary encapsulation, and shaping.

[0114] The full-charge rebound test method is as follows: The lithium-ion battery is charged and discharged at 25°C, within a voltage range of 2.5-4.2 V, at 0.5C. After 100 charge and discharge cycles, the ratio of the increase in electrode thickness to the electrode thickness before charge and discharge is recorded as the full-charge rebound rate, with the electrode fully charged and lithium-intercalated.

[0115] The results are shown in Table 6.

[0116] Table 6

[0117]

[0118] It is evident that the binder of this invention can effectively suppress the full-charge rebound of the electrode.

Claims

1. A water-soluble granular adhesive, characterized in that: The water-soluble granular binder includes organic polymer particles, and the shape of the organic polymer particles is secondary particles formed by the aggregation of primary particles. The polymer monomers of the organic polymer particles include hydrophilic monomers and lipophilic monomers. The hydrophilic monomers include monomers containing double bonds and acids. The weight percentage of hydrophilic monomers and lipophilic monomers is 30-70% : 70-30%.

2. The water-soluble particulate binder according to claim 1, characterized in that: The particle size D50 of primary particles is 1 μm to 1000 μm, and the particle size D50 of secondary particles is 100 μm to 2000 μm.

3. The water-soluble particulate binder according to claim 1, characterized in that: Hydrophilic monomers also include at least one of double-bonded salt monomers and double-bonded amide monomers; lipophilic monomers include at least one of double-bonded benzene ring monomers, double-bonded nitrile monomers, and double-bonded ester monomers.

4. The water-soluble particulate binder according to claim 3, characterized in that: Monomers containing double bonds and acids include at least one of (meth)acrylic acid, (meth)propenesulfonic acid, maleic acid, itaconic acid, 2-acrylamido-2-methylpropanesulfonic acid, allyloxyhydroxypropylsulfonic acid, β-acryloyloxypropionic acid, and 2-fluoroacrylic acid; The monomers containing double bonds include at least one of (meth)acrylate, (meth)propenesulfonate, maleate, itaconic acid, allyloxyhydroxypropyl sulfonate, β-acryloyloxypropionate, and 2-fluoroacrylate; wherein the salt is a lithium salt, sodium salt, or potassium salt. The amide monomers containing double bonds include at least one of acrylamide, methacrylamide, N,N-diethylacrylamide, N,N-diethylmethacrylamide, N-ethylacrylamide, N-ethylmethacrylamide, N,N-dimethylacrylamide, N,N-dimethylmethacrylamide, N-methacrylamide, N-methylmethacrylamide, N-isopropylacrylamide, and N-isopropylmethacrylamide. Monomers containing double-bonded benzene rings include at least one of styrene, methylstyrene, tetrapropylenebenzene, methyl p-vinylphenyl ether, divinylbenzene, stilbene, tristyrene, and tetrastyrene; The nitrile monomers containing double bonds include at least one of acrylonitrile, methacrylonitrile, isobutylenenitrile, 2-pentenenitrile, 5-hexenenitrile, and 6-heptenenitrile; Monomers containing double bonds include methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, hydroxybutyl acrylate, hydroxybutyl methacrylate, butyl acrylate, butyl methacrylate, n-octyl acrylate, isooctyl acrylate, isooctyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, octadecyl acrylate, octadecyl methacrylate, isobornyl acrylate, isobornyl methacrylate, propyl acrylate, isobutyl acrylate, sec-butyl acrylate, tert-butyl acrylate, phenyl methacrylate, hexadecyl acrylate, sulfonyl acrylate, sulfonyl methacrylate, glycidyl methacrylate, tert-butylaminoethyl methacrylate, dimethylaminoethyl methacrylate, tert-butylaminoethyl methacrylate, vinyl methacrylate, benzyl methacrylate, phenyl methacrylate, and hexadecyl methacrylate.

5. The water-soluble particulate binder according to claim 1, characterized in that: By weight, the hydrophilic monomers contain 1 to 70 parts of double-bonded acid monomers, 0 to 70 parts of double-bonded salt monomers, and 0 to 70 parts of double-bonded amide monomers. By weight, the lipophilic monomers contain 0-70 parts of double-bonded benzene ring monomers, 0-70 parts of double-bonded nitrile monomers, and 0-70 parts of double-bonded ester monomers, and the number of double-bonded benzene ring monomers, double-bonded nitrile monomers, and double-bonded ester monomers is not 0 at the same time.

6. The water-soluble particulate binder according to claim 1, characterized in that: The weight-average molecular weight of the organic polymer particles is 300,000 to 3,000,000.

7. The water-soluble particulate binder according to claim 1, characterized in that: Organic polymer particles account for more than 95% of the weight of water-soluble granular binders.

8. A method for preparing the water-soluble particulate binder according to any one of claims 1 to 7, characterized in that, Includes the following steps: 1) Copolymerization: Under a protective atmosphere, the monomer is added to water, an initiator is added to initiate the polymerization reaction, a solid-liquid mixture is obtained, and then the precipitate is collected; 2) Neutralization: Add the precipitate obtained in step 1) to the mixed solvent, stir, and neutralize until the pH of the supernatant is 6.5-9. Take out the polymer, place it in organic solvent A and stir for at least 60 minutes. Take out the polymer and dry it to obtain the water-soluble particulate binder.

9. The method for preparing the water-soluble particulate binder according to claim 8, characterized in that: In step 2), the mixed solvent is organic solvent B and water, and the mass ratio of organic solvent B to water is 30:70 to 95:

5.

10. The method for preparing the water-soluble particulate binder according to claim 9, characterized in that: The mass ratio of organic solvent B to water is 70:

30.

11. The method for preparing the water-soluble particulate binder according to claim 9, characterized in that: The organic solvent A is at least one of N-methylpyrrolidone, isopropanol, ethanol, methanol, and acetonitrile, and the organic solvent B is at least one of N-methylpyrrolidone, isopropanol, ethanol, methanol, and acetonitrile.

12. The application of the water-soluble particulate binder according to any one of claims 1 to 7 in the preparation of lithium-ion battery negative electrode slurry.

13. The application of the soluble particulate binder according to claim 12 in the preparation of lithium-ion battery negative electrode slurry, characterized in that: The negative electrode slurry is a silicon-carbon negative electrode slurry.

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