Emulsion of cathode ceramic slurry for new energy vehicle battery and its preparation method

Abstract

The present invention belongs to the technical field of battery negative electrode ceramic slurries, and particularly relates to an emulsion of a battery negative electrode ceramic slurry for new energy vehicles and a preparation method thereof. The emulsion comprises the following raw materials in parts by weight: 80-90 parts of graphite powder, 7-13 parts of alumina powder, 1-3 parts of styrene-butadiene emulsion, and 0.4-0.7 parts of modified sodium carboxymethylcellulose; the styrene-butadiene emulsion is prepared from raw materials such as styrene, butadiene, acrylic acid, itaconic acid, tert-dodecyl mercaptan, sodium dodecylbenzenesulfonate, and sodium alkylphenol polyoxyethylene ether sulfate. The present invention synergistically uses the styrene-butadiene emulsion with modified sodium carboxymethylcellulose, graphite powder and other raw materials to optimize the rheological properties of the slurry and ensure the comprehensive performance of the electrode sheet.

Description

Technical Field

[0001] The present invention belongs to the technical field of battery negative electrode ceramic slurries, and particularly relates to an emulsion of a battery negative electrode ceramic slurry for new energy vehicles and a preparation method thereof. Background Art

[0002] In the field of new energy vehicles, battery performance is one of the key factors determining the overall performance of vehicles. With the rapid development of the new energy vehicle market, higher and higher requirements are put forward for aspects such as the energy density, charge and discharge efficiency, cycle life, and safety of batteries. As an important part of the battery, the performance of the battery negative electrode material directly affects various performance indicators of the battery. When facing the increasing performance requirements, traditional battery negative electrode materials gradually expose some limitations. For example, during high-rate charge and discharge processes, the structural stability of the electrode material is insufficient, which easily leads to rapid capacity decay and affects the cycle life of the battery; in addition, the conductivity of some negative electrode materials is limited, which to a certain extent restricts the charge and discharge efficiency of the battery and cannot meet the requirements of new energy vehicles in aspects such as fast charging. To overcome these problems, researchers have begun to explore new negative electrode materials and preparation technologies. Due to their unique physical and chemical properties, such as high hardness, high chemical stability, and good high-temperature resistance, ceramic materials have gradually been introduced into the research of battery negative electrode materials.

[0003] The patent with the application number CN201811568275.X provides a negative electrode composite slurry, its preparation method, and a lithium battery negative electrode sheet. The negative electrode composite slurry is formed by mixing ultrafine glass fibers, ceramic powder, binder one, binder two, styrene-butadiene emulsion or styrene-acrylic emulsion, and water in a certain proportion. Using the composite slurry to prepare a lithium battery negative electrode sheet can effectively improve the safety performance of the lithium battery. By mixing ultrafine glass fibers and ceramic powder in the negative electrode composite slurry, the two are evenly dispersed to form a negative electrode composite coating with a three-dimensional structure, which not only ensures the heat insulation effect but also has good lithium ion transmission effect, reduces the problem of lithium ion diffusion channel blockage, and ensures the rate performance of the lithium battery. Experimental results show that the lithium battery using this negative electrode composite slurry has significantly improved safety in the nail penetration test, and the capacity retention rate is also significantly better than that of the comparative battery without adding ultrafine glass fibers. As a binder material used in the lithium battery negative electrode, although the amount of styrene-butadiene emulsion in the lithium battery negative electrode material system is small, it plays a crucial role in the battery performance. Given that lithium batteries will be applied in various complex environments, from high temperature to low temperature, from high humidity to severe mechanical vibration scenarios, etc., this has put forward more stringent requirements for various indicators of styrene-butadiene emulsion. The patent with the application number CN202110355747.9 provides a preparation method of a ceramic slurry, a ceramic separator, and a lithium ion battery. The preparation method of the ceramic slurry adds a stabilizer, a dispersant, ceramic powder, etc. in sequence and disperses them through specific steps, processes them with a sand mill, and finally adds a wetting agent to obtain the ceramic slurry; the slurry prepared by this method has good stability, is evenly dispersed, and is not easy to stratify or agglomerate. The ceramic separator prepared using this slurry is obtained by coating and baking on a base film, has high air permeability and good heat resistance, and the safety performance of the lithium ion battery containing this separator is significantly improved and the service life is extended. Experimental results show that compared with the comparative method, the slurry prepared by the inventive method has better stability, dispersion uniformity, and wettability, and the ceramic separator prepared has better air permeability. However, although sodium carboxymethylcellulose can play an important role as a stabilizer in the ceramic slurry, there are also some potential disadvantages. The flexibility of sodium carboxymethylcellulose is relatively poor, which will cause cracks or uneven coating layers during the coating process of the slurry, thereby affecting the overall performance of the ceramic separator. In addition, under different pH values or ionic strengths, the solubility and stability of sodium carboxymethylcellulose will change, which will cause stratification or precipitation phenomena during the storage or use of the slurry, affecting the uniformity and stability of the slurry. Summary of the Invention

[0004] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide an emulsion of a negative electrode ceramic slurry for a new energy vehicle battery and a preparation method thereof. A modified carboxymethyl cellulose sodium is prepared by three-step chemical reactions. By introducing long-chain alkyl groups, amide groups and ester groups, the adhesion to the active material is enhanced, and the flexibility and dispersion stability of the slurry are improved. The modified carboxymethyl cellulose sodium and styrene-butadiene emulsion, graphite powder, etc. act synergistically to optimize the rheological properties, improve the coating uniformity, and ensure the overall performance of the electrode sheet.

[0005] The technical solution adopted by the present invention to achieve the above object is as follows:

[0006] An emulsion of a negative electrode ceramic slurry for a new energy vehicle battery, comprising the following raw materials in parts by weight: 80-90 parts of graphite powder, 7-13 parts of alumina powder, 1-3 parts of styrene-butadiene emulsion, and 0.4-0.7 part of modified carboxymethyl cellulose sodium;

[0007] The styrene-butadiene emulsion comprises the following raw materials in parts by weight: 25-35 parts of styrene, 20-25 parts of butadiene, 1-3 parts of acrylic acid, 0.5-1 part of itaconic acid, 0.2-0.5 part of tert-dodecyl mercaptan, 0.4-0.6 part of sodium dodecylbenzenesulfonate, 0.5-2 parts of sodium alkylphenol polyoxyethylene ether sulfate, 1-2 parts of acrylamide, 0.4-1 part of sodium persulfate, 0.1-1 part of solid caustic soda, 0.1-0.2 part of liquid caustic soda, 40-50 parts of water, 0.5-1.0 part of defoamer, and 0.5-1.0 part of preservative.

[0008] Furthermore, the preparation method of the modified carboxymethyl cellulose sodium is as follows:

[0009] S1. Under a nitrogen atmosphere and stirring conditions, methyl oleate is dispersed in absolute ethanol, then ethanolamine is added and mixed evenly. Then, a methanol sodium methanol solution is added dropwise, and the addition is completed within 0.5-1.5 h. The temperature is raised to 40-60 °C, and the reaction is carried out for 6-8 h. After cooling and purification, an intermediate is obtained;

[0010] S2. Under stirring conditions, 2,5-dimethylhexanoic acid is dispersed in N,N-dimethylformamide, then the intermediate obtained in step S1 and p-toluenesulfonic acid are added, and the temperature is raised to 75-95 °C, and the reaction is carried out for 6-10 h. After cooling and purification, a modified oleate is obtained;

[0011] S3. Carboxymethyl cellulose sodium is dispersed in deionized water, and stirred at 55-65 °C until dissolved. After cooling to room temperature, an aqueous solution of potassium persulfate is added dropwise, and the addition is completed within 40-60 min. Stirring is continued for 10-20 min, then the modified oleate obtained in step S2 is added, and the temperature is raised to 70-90 °C, and the stirring reaction is carried out for 2-4 h. After cooling and purification, modified carboxymethyl cellulose sodium is obtained;

[0012] Among them, the synthesis route of the modified oleate is as follows:

[0013] ;

[0014] .

[0015] In the present invention, methyl oleate and ethanolamine are used as starting materials, and an intermediate is obtained under the catalysis of sodium methoxide; then, using the intermediate and 2,5-dimethylhexanoic acid as raw materials, a modified oleate is obtained under the action of p-toluenesulfonic acid; finally, using the modified oleate as a modifier, carboxymethyl cellulose sodium is chemically grafted under the action of potassium persulfate to obtain modified carboxymethyl cellulose sodium.

[0016] In order to functionalize and modify carboxymethyl cellulose sodium, in step S1, the mass ratio of methyl oleate to ethanolamine is 10-15:4, the addition amount of methyl oleate in absolute ethanol is 0.15-0.20 g / mL, the volume ratio of absolute ethanol to sodium methoxide methanol solution is 40:5-10, and the molar concentration of the sodium methoxide methanol solution is 3.5-4.5 mol / L; in step S2, the mass ratio of 2,5-dimethylhexanoic acid, the intermediate, and p-toluenesulfonic acid is 2-3:5:0.08-0.12, and the addition amount of 2,5-dimethylhexanoic acid in N,N-dimethylformamide is 0.18-0.26 g / mL; in step S3, the mass ratio of carboxymethyl cellulose sodium to the modified oleate is 1:0.5-0.8, the addition amount of carboxymethyl cellulose sodium in deionized water is 0.08-0.11 g / mL, the volume ratio of deionized water to the potassium persulfate aqueous solution is 10:0.3-0.5, and the molar concentration of the potassium persulfate aqueous solution is 0.09-0.11 mol / L.

[0017] Furthermore, the defoaming agent is polydimethylsiloxane; the preservative is one or several of phenoxyethanol, ethylhexylglycerin, and p-hydroxybenzoic acid.

[0018] Furthermore, the preparation method of the styrene-butadiene latex is as follows:

[0019] (1) Add acrylic acid, solid caustic soda, and 0.15-0.25 parts of sodium dodecylbenzenesulfonate to 22-26 parts of water, stir until dissolved to obtain an aqueous phase;

[0020] (2) Add tert-dodecyl mercaptan to 20-23 parts of styrene, stir for 20-40 min to obtain an oil phase;

[0021] (3) Under stirring conditions, sodium alkylphenol polyoxyethylene ether sulfate, acrylamide, itaconic acid, 0.5 - 2.5 parts of butadiene, the remaining sodium dodecylbenzenesulfonate, and the remaining styrene are added to the remaining water. After vacuum pumping, the temperature is raised to 75 - 80 °C, 0.2 - 0.3 parts of sodium persulfate are added, and the reaction is carried out at 93 - 97 °C for 20 - 40 min. Then, the aqueous phase, oil phase, the remaining sodium persulfate, and the remaining butadiene are added, and the mixture is kept warm at 95 - 100 °C for 0.5 - 1.5 h. Finally, liquid alkali is added, and 0.2 - 0.4 parts of defoamer are added for physical degassing. After natural cooling to 45 °C, preservative and the remaining defoamer are added, mixed evenly, filtered, and discharged to obtain the product.

[0022] The present invention also provides a preparation method for an emulsion of a battery negative electrode ceramic slurry for new energy vehicles, comprising the following steps: dispersing modified sodium carboxymethyl cellulose in deionized water, stirring at 60 - 70 °C until dissolved, cooling to room temperature, adding styrene-butadiene latex, and stirring for 15 - 25 min to obtain a mixed emulsion; mechanically mixing graphite powder and alumina powder to obtain a mixed powder; adding the mixed emulsion to the mixed powder, stirring for 40 - 60 min, then grinding, and removing bubbles by vacuum after sieving to obtain the product.

[0023] The present invention has the following beneficial effects:

[0024] The present invention uses a three-step method to introduce long-chain alkyl groups, amide groups, and ester groups into the molecular structure of sodium carboxymethyl cellulose, significantly improving its performance in the emulsion of the battery negative electrode ceramic slurry. The introduction of long-chain alkyl groups builds a "flexible bridge" between molecular chains, which can increase the movement space between molecular chains, weaken the binding force between molecular chains, enable them to move and deform more freely, and during the processing of the electrode sheet such as rolling and bending, the molecular chains can better adapt to external forces through this free movement, thereby reducing the occurrence of brittle fractures and greatly improving the flexibility of the sodium carboxymethyl cellulose-based composite material. The introduction of long-chain alkyl groups and amide groups changes the surface properties of the slurry system. The long-chain alkyl groups, due to their own structural characteristics, enhance the interaction with the active substances, making the slurry dispersion more uniform. The amide groups can adsorb on the surface of the active material particles through their own polarity and steric hindrance to prevent the particles from aggregating due to mutual attraction. The combined action of these two groups improves the surface energy of the slurry and reduces the aggregation phenomenon between particles, thereby enhancing the dispersion stability of the slurry. In addition, the amide groups have high polarity, which can not only form hydrogen bonds with functional groups such as hydroxyl groups and carboxyl groups on the surface of the current collector to improve the bonding performance of the composite slurry, but also form a hydrogen bond network between the modified sodium carboxymethyl cellulose molecules to enhance the intermolecular force. When subjected to external forces, this network can disperse the stress and prevent the active material from detaching from the current collector due to local stress concentration, thereby further improving the bonding performance and peel strength of the composite slurry.

[0025] The modified sodium carboxymethyl cellulose can improve the bonding performance of the system. As a binder supplement, styrene-butadiene latex binds graphite powder, alumina powder, etc. firmly together and attaches them to the current collector, forming a stable electrode structure, reducing the shedding and loss of active substances, thus ensuring the normal insertion and extraction of lithium ions, and further improving the high-temperature capacity retention rate of the electrode sheet. The modified sodium carboxymethyl cellulose synergistically acts with styrene-butadiene latex and other additives to uniformly disperse the active materials in the slurry, avoiding agglomeration and sedimentation, ensuring the uniformity and stability of the slurry, optimizing the coating process, and ensuring the consistency of the electrode sheet. When the modified sodium carboxymethyl cellulose is used in combination with other materials and coated on the surface of the current collector, it can form a denser membrane structure, improve the conductivity of the electrode sheet, and further help reduce the resistivity of the electrode sheet. Specific embodiments

[0026] The technical solutions in the embodiments of the present application will be clearly and completely described below in conjunction with the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present application.

[0027] Sodium carboxymethyl cellulose, with a density of 1.6 g / cm³ and a melting point of 274 °C, was purchased from Baiyundu Biotechnology Co., Ltd.; graphite powder, with a mesh number of 1000 mesh and a fixed carbon content of 99.99%, model PWGX-22(1000), was purchased from Jiaxing Nake New Materials Co., Ltd.; alumina powder, with a mesh number of 800 mesh, model JC-A30P, was purchased from Qinghe County Chaotai Metal Materials Co., Ltd.; sodium alkylphenol polyoxyethylene ether sulfate, with an active substance content of 80%, model OP4SA, was purchased from Nantong Aches Chemical Co., Ltd.; polydimethylsiloxane, model 201, was purchased from Jinan Yingyu Chemical Co., Ltd. The raw materials used in the following examples are all ordinary commercially available products. Example 1

[0028] An emulsion of a negative electrode ceramic slurry for a new energy vehicle battery comprises the following raw materials in parts by weight: 85 parts of graphite powder, 11 parts of alumina powder, 2 parts of styrene-butadiene latex, and 0.6 part of modified sodium carboxymethyl cellulose;

[0029] The preparation method of the modified sodium carboxymethyl cellulose is as follows:

[0030] S1. Under a nitrogen atmosphere and stirring conditions, disperse methyl oleate in absolute ethanol, then add ethanolamine and mix evenly. Then, dropwise add a sodium methoxide methanol solution, and finish the addition within 1 h. Heat up to 50 °C and react for 7 h. After the reaction is completed, naturally cool to room temperature, and obtain an intermediate through vacuum distillation and vacuum drying. Among them, the mass ratio of methyl oleate to ethanolamine is 12:4, the addition amount of methyl oleate in absolute ethanol is 0.18 g / mL, the volume ratio of absolute ethanol to the sodium methoxide methanol solution is 40:7, and the molar concentration of the sodium methoxide methanol solution is 4 mol / L.

[0031] S2. Under stirring conditions, disperse 2,5-dimethylhexanoic acid in N,N-dimethylformamide, then add the intermediate obtained in step S1 and p-toluenesulfonic acid, heat up to 85 °C, react for 8 h, naturally cool to room temperature, add a saturated sodium bicarbonate aqueous solution, continue stirring for 40 min, then add ethyl acetate for extraction, separate the layers, and obtain an ester phase. After vacuum distillation and vacuum drying, obtain a modified oleate. Among them, the mass ratio of 2,5-dimethylhexanoic acid, the intermediate, and p-toluenesulfonic acid is 2.5:5:0.1, the addition amount of 2,5-dimethylhexanoic acid in N,N-dimethylformamide is 0.22 g / mL, and the volume ratio of N,N-dimethylformamide, the saturated sodium bicarbonate aqueous solution, and ethyl acetate is 1:1:2.

[0032] The NMR results of the modified oleate are as follows: 1 H NMR(300MHz, DMSO-d6) δ 8.01 (s, 1H), 5.43 (t, 2H), 4.34 (t, 2H), 3.28 (t, 2H), 2.32 - 2.35 (m, 1H), 2.13 - 2.16 (m, 6H), 1.55 - 1.60 (m, 5H), 1.26 - 1.30 (m, 20H), 1.12 - 1.16 (m, 5H), 0.88 - 0.91 (m, 9H);

[0033] S3. Disperse sodium carboxymethyl cellulose in deionized water, stir at 60 °C until dissolved, cool naturally to room temperature, then dropwise add an aqueous solution of potassium persulfate, complete the dropwise addition in 50 min, continue stirring for 15 min, then add the modified oleate obtained in step S2, raise the temperature to 80 °C, stir and react for 3 h, cool naturally to room temperature, perform precipitation separation with 95% ethanol, extract with acetone in a Soxhlet extractor for 10 h after drying, and vacuum dry to obtain modified sodium carboxymethyl cellulose. The grafting rate of the modified sodium carboxymethyl cellulose is 23.6%. The mass ratio of the sodium carboxymethyl cellulose to the modified oleate is 1:0.7. The addition amount of sodium carboxymethyl cellulose in the deionized water is 0.09 g / mL. The volume ratio of the deionized water to the aqueous solution of potassium persulfate is 10:0.4. The molar concentration of the aqueous solution of potassium persulfate is 0.1 mol / L. The calculation formula for the grafting rate of the modified sodium carboxymethyl cellulose is: grafting rate (%) = (output of modified sodium carboxymethyl cellulose - input amount of sodium carboxymethyl cellulose) / input amount of sodium carboxymethyl cellulose × 100%.

[0034] The styrene-butadiene emulsion comprises the following raw materials in parts by weight: 30 parts of styrene, 20 parts of butadiene, 1 part of acrylic acid, 0.5 part of itaconic acid, 0.2 part of tert-dodecyl mercaptan, 0.5 part of sodium dodecylbenzenesulfonate, 0.5 part of sodium alkylphenol polyoxyethylene ether sulfate, 1 part of acrylamide, 0.5 part of sodium persulfate, 0.3 part of solid caustic soda, 0.2 part of liquid caustic soda, 48 parts of water, 0.5 part of defoaming agent, 0.5 part of preservative; the defoaming agent is polydimethylsiloxane, and the preservative is phenoxyethanol;

[0035] The preparation method of the styrene-butadiene emulsion is as follows:

[0036] (1) Prepare the aqueous phase: Add 24 parts of water to the reactor, start stirring, then add acrylic acid, caustic soda flakes, and 0.2 part of sodium dodecylbenzenesulfonate, and stir for 1 h until completely dissolved;

[0037] (2) Prepare the oil phase: Add 23 parts of styrene to the reactor, start stirring, add tert-dodecyl mercaptan, and stir for 30 min;

[0038] (3) Add the remaining water into the reaction kettle, start stirring, add sodium alkylphenol polyoxyethylene ether sulfate, acrylamide, itaconic acid, 1.5 parts of butadiene, the remaining sodium dodecylbenzenesulfonate and the remaining styrene. Then evacuate the reaction kettle to -0.07 MPa, fill it with nitrogen to 0 MPa, evacuate it to -0.07 MPa again, heat up to 78 °C, quickly add 0.2 parts of sodium persulfate, control the reaction temperature at 95 °C, and the reaction time is 30 min. Then feed the aqueous phase, oil phase, the remaining sodium persulfate and the remaining butadiene, control the feeding temperature at 90 °C, and the feeding time is 4.5 h. After the feeding is completed, keep it warm at 98 °C for 1 h, add liquid alkali to adjust the pH value, and add 0.3 parts of defoamer for physical degassing. Naturally cool down to 45 °C, add preservative and the remaining defoamer, mix evenly, filter through a 325-mesh sieve, and discharge to obtain. The solid content of the styrene-butadiene emulsion prepared in this example is 50%, the viscosity < 300 cp, the particle size is 120 - 160 nm, and the pH is 6 - 7.

[0039] A preparation method of an emulsion for the negative electrode ceramic slurry of a new energy vehicle battery includes the following steps: Disperse modified sodium carboxymethyl cellulose in deionized water, stir until dissolved at 65 °C, cool to room temperature, add styrene-butadiene emulsion, and stir for 20 min at 250 rpm to obtain a mixed emulsion; Mechanically mix graphite powder and alumina powder, with a stirring speed of 40 rpm and a time of 20 min to obtain a mixed powder; Add the mixed emulsion to the mixed powder, stir for 50 min at 450 rpm and then carry out ball milling. Use zirconia balls for ball milling treatment. The diameter of the zirconia balls is 2.0 mm, the rotation speed of the ball milling treatment is 40 rpm, the ball milling time is 3 h, the ball-to-material ratio is 4:1. After the ball milling is completed, pass through a 325-mesh sieve and vacuum-remove bubbles to obtain. Among them, the mass ratio of modified sodium carboxymethyl cellulose to deionized water is 0.6:70. Example 2

[0040] An emulsion for the negative electrode ceramic slurry of a new energy vehicle battery includes the following raw materials in parts by weight: 80 parts of graphite powder, 7 parts of alumina powder, 1 part of styrene-butadiene emulsion, 0.4 part of modified sodium carboxymethyl cellulose;

[0041] The preparation method of the modified sodium carboxymethyl cellulose is as follows:

[0042] S1. Under a nitrogen atmosphere and stirring conditions, disperse methyl oleate in absolute ethanol, then add ethanolamine and mix evenly. Then, dropwise add a sodium methoxide methanol solution, and finish the dropping within 0.5 h. Heat up to 60 °C and react for 6 h. After the reaction is completed, naturally cool to room temperature, and obtain the intermediate through vacuum distillation and vacuum drying. Among them, the mass ratio of methyl oleate to ethanolamine is 10:4, the addition amount of methyl oleate in absolute ethanol is 0.15 g / mL, the volume ratio of absolute ethanol to the sodium methoxide methanol solution is 40:5, and the molar concentration of the sodium methoxide methanol solution is 3.5 mol / L.

[0043] S2. Under stirring conditions, disperse 2,5-dimethylhexanoic acid in N,N-dimethylformamide, then add the intermediate obtained in step S1 and p-toluenesulfonic acid, heat up to 95 °C and react for 6 h. Naturally cool to room temperature, add a saturated sodium bicarbonate aqueous solution, continue stirring for 40 min, then add ethyl acetate for extraction and liquid separation to obtain an ester phase, and obtain the modified oleate through vacuum distillation and vacuum drying. Among them, the mass ratio of 2,5-dimethylhexanoic acid, the intermediate, and p-toluenesulfonic acid is 2:5:0.08, the addition amount of 2,5-dimethylhexanoic acid in N,N-dimethylformamide is 0.18 g / mL, and the volume ratio of N,N-dimethylformamide, the saturated sodium bicarbonate aqueous solution, and ethyl acetate is 1:1:2.

[0044] S3. Disperse sodium carboxymethyl cellulose in deionized water, stir until dissolved at 65 °C, naturally cool to room temperature, then dropwise add an aqueous potassium persulfate solution, and finish the dropping within 40 min. Continue stirring for 10 min, then add the modified oleate obtained in step S2, heat up to 90 °C, and stir and react for 2 h. Naturally cool to room temperature, perform precipitation separation with 95% ethanol, and after drying, extract with acetone in a Soxhlet extractor for 10 h, and vacuum dry to obtain modified sodium carboxymethyl cellulose. The grafting rate of the modified sodium carboxymethyl cellulose is 23.6%. Among them, the mass ratio of sodium carboxymethyl cellulose to the modified oleate is 1:0.5, the addition amount of sodium carboxymethyl cellulose in deionized water is 0.08 g / mL, the volume ratio of deionized water to the aqueous potassium persulfate solution is 10:0.3, and the molar concentration of the aqueous potassium persulfate solution is 0.09 mol / L. The calculation formula for the grafting rate of the modified sodium carboxymethyl cellulose is: grafting rate (%) = (output of modified sodium carboxymethyl cellulose - input amount of sodium carboxymethyl cellulose) / input amount of sodium carboxymethyl cellulose × 100%.

[0045] The styrene-butadiene emulsion comprises raw materials in the following parts by weight: 25 parts of styrene, 25 parts of butadiene, 2 parts of acrylic acid, 0.4 part of itaconic acid, 0.5 part of tert-dodecyl mercaptan, 0.4 part of sodium dodecylbenzenesulfonate, 1 part of sodium alkylphenol polyoxyethylene ether sulfate, 2 parts of acrylamide, 0.8 part of sodium persulfate, 0.6 part of solid caustic soda, 0.1 part of liquid caustic soda, 44 parts of pure water, 0.8 part of defoamer, and 0.7 part of preservative; the defoamer is polydimethylsiloxane, and the preservative is ethylhexylglycerol;

[0046] The preparation method of the styrene-butadiene emulsion is as follows:

[0047] (1) Prepare the aqueous phase: Add 22 parts of water to the reactor, start stirring, then add acrylic acid, caustic soda flakes, and 0.15 part of sodium dodecylbenzenesulfonate, and stir for 1 h until completely dissolved;

[0048] (2) Prepare the oil phase: Add 20 parts of styrene to the reactor, start stirring, add tert-dodecyl mercaptan, and stir for 20 min;

[0049] (3) Add the remaining water to the reaction kettle, start stirring, add sodium alkylphenol polyoxyethylene ether sulfate, acrylamide, itaconic acid, 0.5 part of butadiene, the remaining sodium dodecylbenzenesulfonate, and the remaining styrene, then evacuate the reaction kettle to -0.07 MPa, fill it with nitrogen to 0 MPa, evacuate it to -0.07 MPa again, raise the temperature to 75 °C, quickly add 0.3 part of sodium persulfate, control the reaction temperature at 93 °C, keep the reaction time for 40 min, then feed the aqueous phase, oil phase, the remaining sodium persulfate, and the remaining butadiene, control the feeding temperature at 90 °C, keep the feeding time for 4.5 h, after the feeding is completed, keep it warm at 95 °C for 1.5 h, add liquid caustic soda to adjust the pH value, add 0.2 part of defoamer for physical degassing, naturally cool it to 45 °C, add the preservative and the remaining defoamer, mix evenly, filter through a 325-mesh sieve, and discharge to obtain; the solid content of the styrene-butadiene emulsion prepared in this example is 50.5%, the viscosity < 300 cp, the particle size is 120 - 160 nm, and the pH is 6 - 7.

[0050] A method for preparing an emulsion of anode ceramic slurry for a battery for new energy vehicles comprises the following steps: dispersing modified sodium carboxymethyl cellulose in deionized water, stirring at 70°C until dissolved, cooling to room temperature, adding styrene butadiene emulsion, stirring at 250rpm for 15min to obtain a mixed emulsion; mechanically solid-phase mixing graphite powder and alumina powder at a stirring speed of 40rpm for 20min to obtain a mixed powder; adding the mixed emulsion to the mixed powder, stirring at 450rpm for 40min, and then ball milling, using zirconium oxide balls for ball milling, the diameter of the zirconium oxide balls is 2.0mm, the rotation speed of the ball milling is 40rpm, the ball milling time is 3h, the ball-to-material ratio is 4:1, and after ball milling, passing through a 325-mesh sieve, and vacuum removing bubbles to obtain the product; wherein the mass ratio of modified sodium carboxymethyl cellulose to deionized water is 0.6:70. Example 3

[0051] An emulsion of anode ceramic slurry for a new energy vehicle battery comprises the following raw materials in parts by weight: 90 parts of graphite powder, 13 parts of alumina powder, 3 parts of styrene-butadiene emulsion, and 0.7 parts of modified sodium carboxymethyl cellulose;

[0052] The preparation method of the modified sodium carboxymethyl cellulose is:

[0053] S1. In a nitrogen atmosphere and under stirring conditions, methyl oleate is dispersed in anhydrous ethanol, ethanolamine is added, mixed evenly, and then a methanol solution of sodium methoxide is added dropwise. The addition is completed in 1.5 hours, the temperature is raised to 40°C, and the reaction is performed for 8 hours. After the reaction is completed, the mixture is naturally cooled to room temperature, and the mixture is subjected to reduced pressure distillation and vacuum drying to obtain an intermediate; wherein the mass ratio of the methyl oleate to the ethanolamine is 15:4, the amount of methyl oleate added to the anhydrous ethanol is 0.2 g / mL, the volume ratio of the anhydrous ethanol to the methanol solution of sodium methoxide is 40:10, and the molar concentration of the methanol solution of sodium methoxide is 4.5 mol / L;

[0054] S2, under stirring conditions, 2,5-dimethylhexanoic acid is dispersed in N,N-dimethylformamide, and then the intermediate obtained in step S1 and p-toluenesulfonic acid are added, the temperature is raised to 75°C, the reaction is carried out for 10 hours, and the mixture is naturally cooled to room temperature, a saturated sodium bicarbonate aqueous solution is added, stirring is continued for 40 minutes, and then ethyl acetate is added for extraction, and the liquid is separated to obtain an ester phase, and the ester phase is subjected to reduced pressure distillation and vacuum drying to obtain a modified oleic acid ester; wherein the mass ratio of the 2,5-dimethylhexanoic acid, the intermediate, and p-toluenesulfonic acid is 3:5:0.12, the amount of 2,5-dimethylhexanoic acid added to N,N-dimethylformamide is 0.26 g / mL, and the volume ratio of N,N-dimethylformamide, saturated sodium bicarbonate aqueous solution, and ethyl acetate is 1:1:2;

[0055] S3. Disperse sodium carboxymethyl cellulose in deionized water, stir at 55 °C until dissolved, naturally cool to room temperature, then dropwise add an aqueous solution of potassium persulfate, complete the dropwise addition within 60 min, continue stirring for 20 min, then add the modified oleate obtained in step S2, raise the temperature to 70 °C, stir and react for 4 h, naturally cool to room temperature, perform precipitation separation with 95% ethanol, extract with acetone in a Soxhlet extractor for 10 h after drying, and vacuum dry to obtain modified sodium carboxymethyl cellulose. The grafting rate of the modified sodium carboxymethyl cellulose is 23.6%; wherein the mass ratio of sodium carboxymethyl cellulose to the modified oleate is 1:0.8, the addition amount of sodium carboxymethyl cellulose in the deionized water is 0.11 g / mL, the volume ratio of deionized water to the aqueous solution of potassium persulfate is 10:0.5, and the molar concentration of the aqueous solution of potassium persulfate is 0.11 mol / L. The calculation formula for the grafting rate of the modified sodium carboxymethyl cellulose is: grafting rate (%) = (output of modified sodium carboxymethyl cellulose - input amount of sodium carboxymethyl cellulose) / input amount of sodium carboxymethyl cellulose × 100%.

[0056] The styrene-butadiene emulsion comprises the following raw materials in parts by weight: 35 parts of styrene, 25 parts of butadiene, 3 parts of acrylic acid, 1 part of itaconic acid, 0.5 part of tert-dodecyl mercaptan, 0.6 part of sodium dodecylbenzenesulfonate, 1.5 parts of sodium alkylphenol polyoxyethylene ether sulfate, 1.5 parts of acrylamide, 0.4 part of sodium persulfate, 0.1 part of solid caustic soda, 0.8 part of liquid caustic soda, 50 parts of pure water, 1 part of defoaming agent, and 1 part of preservative; the defoaming agent is polydimethylsiloxane, and the preservative is p-hydroxybenzoic acid;

[0057] The preparation method of the styrene-butadiene emulsion is as follows:

[0058] (1) Prepare the aqueous phase: Add 26 parts of water to the reactor, start stirring, then add acrylic acid, caustic soda flakes, and 0.25 part of sodium dodecylbenzenesulfonate, and stir for 1 h until completely dissolved;

[0059] (2) Prepare the oil phase: Add 23 parts of styrene to the reactor, start stirring, add tert-dodecyl mercaptan, and stir for 40 min;

[0060] (3) Add the remaining water to the reaction kettle, start stirring, add sodium alkylphenol polyoxyethylene ether sulfate, acrylamide, itaconic acid, 2.5 parts of butadiene, the remaining sodium dodecylbenzenesulfonate and the remaining styrene. Then evacuate the reaction kettle to -0.07 MPa, fill it with nitrogen to 0 MPa, evacuate it to -0.07 MPa again, heat it up to 80 °C, quickly add 0.25 parts of sodium persulfate, control the reaction temperature at 97 °C, and the reaction time is 20 min. Then feed the aqueous phase, oil phase, the remaining sodium persulfate and the remaining butadiene, control the feeding temperature at 90 °C, and the feeding time is 4.5 h. After the feeding is completed, keep it warm at 100 °C for 0.5 h, add liquid alkali to adjust the pH value, and add 0.4 parts of defoamer for physical degassing. Naturally cool it to 45 °C, add preservative and the remaining defoamer, mix evenly, filter it through a 325-mesh sieve, and discharge it to obtain; the solid content of the styrene-butadiene latex prepared in this example is 49.5%, the viscosity < 300 cp, the particle size is 120 - 160 nm, and the pH is 6 - 7.

[0061] A preparation method of an emulsion for a battery negative electrode ceramic slurry for a new energy vehicle, comprising the following steps: Disperse modified sodium carboxymethyl cellulose in deionized water, stir it at 60 °C until dissolved, cool it to room temperature, add styrene-butadiene latex, and stir it at 250 rpm for 25 min to obtain a mixed emulsion; Mechanically mix graphite powder and alumina powder, the stirring speed is 40 rpm, and the time is 20 min to obtain a mixed powder; Add the mixed emulsion to the mixed powder, stir it at 450 rpm for 60 min and then carry out ball milling. Use zirconia balls for ball milling treatment, the diameter of the zirconia balls is 2.0 mm, the rotation speed of the ball milling treatment is 40 rpm, the ball milling time is 3 h, the ball-to-material ratio is 4:1. After the ball milling is completed, pass it through a 325-mesh sieve and vacuum-remove the bubbles to obtain; wherein, the mass ratio of modified sodium carboxymethyl cellulose to deionized water is 0.6:70. Example 4

[0062] An emulsion for a battery negative electrode ceramic slurry for a new energy vehicle, comprising the following raw materials in parts by weight: 83 parts of graphite powder, 10 parts of alumina powder, 2 parts of the styrene-butadiene latex prepared in Example 1, and 0.5 part of the modified sodium carboxymethyl cellulose prepared in Example 1.

[0063] A preparation method of an emulsion of a negative electrode ceramic slurry for a new energy vehicle battery, comprising the following steps: dispersing modified sodium carboxymethyl cellulose in deionized water, stirring until dissolved at 65 °C, cooling to room temperature, adding styrene-butadiene emulsion, and stirring at 250 rpm for 22 min to obtain a mixed emulsion; mechanically mixing graphite powder and alumina powder at a stirring speed of 40 rpm for 30 min to obtain a mixed powder; adding the mixed emulsion to the mixed powder, stirring at 450 rpm for 55 min, then performing ball milling, using zirconia balls for ball milling treatment, the diameter of the zirconia balls being 2.0 mm, the rotation speed of the ball milling treatment being 40 rpm, the ball milling time being 3 h, the ball-to-material ratio being 4:1, and after the ball milling is completed, passing through a 325-mesh sieve and vacuum removing air bubbles to obtain the product; wherein, the mass ratio of modified sodium carboxymethyl cellulose to deionized water is 0.6:70. Comparative Example 1

[0064] An emulsion of a negative electrode ceramic slurry for a new energy vehicle battery, comprising the following raw materials in parts by weight: 85 parts of graphite powder, 11 parts of alumina powder, 0.7 part of sodium carboxymethyl cellulose, and 2 parts of the styrene-butadiene emulsion prepared in Example 1.

[0065] A preparation method of an emulsion of a negative electrode ceramic slurry for a new energy vehicle battery is prepared according to the method described in Example 1. Comparative Example 2

[0066] An emulsion of a negative electrode ceramic slurry for a new energy vehicle battery, comprising the following raw materials in parts by weight: 85 parts of graphite powder, 11 parts of alumina powder, 0.7 part of the modified sodium carboxymethyl cellulose prepared in Example 1, and 3 parts of a commercially available styrene-butadiene emulsion (solid content 48%, relative density 0.95).

[0067] A preparation method of an emulsion of a negative electrode ceramic slurry for a new energy vehicle battery is prepared according to the method described in Example 1.

[0068] Perform relevant performance tests on the emulsions of the battery anode ceramic slurries prepared in Examples 1-4 and Comparative Examples 1-2. Dispersion stability test: Place the sample at a temperature of 25 °C and a humidity of 55% for 10 days, and observe the sedimentation state of the sample. Coat the emulsion of the battery anode ceramic slurry on the copper foil. After coating, dry it (bake at 105 °C for 2 h), roll press and die cut to obtain the anode sheet. The coating layer thickness is 80 μm. Observe the coating effect and conduct peel strength, flexibility, sheet resistivity, and high-temperature capacity retention rate tests; Peel strength test: Cut the sample into specimens with a length of 300 mm and a width of 10 mm. Fix the specimen on the steel plate with double-sided tape. Insert the steel plate side into the lower fixed clamp of the tensile machine, and insert the sheet side into the upper fixed clamp. Set the peel distance to 100 mm and the peel speed to 100 mm / min, and record the peel force during the test; Flexibility test: Conduct the test using the coiling needle experiment. The coiling needle diameter is 3.5 mm < d < 4.5 mm, and record the cracking situation of the specimen; Sheet resistivity test: Cut the sample into specimens with a diameter of 1.5 cm and conduct the test on a BER1300 sheet resistance meter; High-temperature capacity retention rate test: Weld the conductive electrode ears on the aluminum foil anode sheet and the above-mentioned anode sheet. Place the polyethylene separator between the anode sheet and the anode sheet, wind it into a bare battery cell and wrap it in an aluminum plastic film, and inject an electrolyte composed of EC∶EMC∶DEC volume ratio = 1∶1∶1 (containing 1.0 M of LiPF 6 ) and perform encapsulation, then form the battery. Control the test environment temperature to be (25 ± 2) °C. Charge the battery at a constant current of 0.5C to 4.25V, then charge it at a constant voltage of 4.25V until the current is 0.05C, let it stand for 10 min, and then discharge it at a constant current of 0.5C to 2.8V, and record the discharge capacity at 25 °C; Then control the test environment temperature to be (60 ± 2) °C. Charge the battery at a constant current of 0.5C to 4.25V, then charge it at a constant voltage of 4.25V until the current is 0.05C, let it stand for 10 min, and then discharge it at a constant current of 0.5C to 2.8V, and record the discharge capacity at 60 °C, and calculate the high-temperature capacity retention rate. The calculation formula is: High-temperature capacity retention rate (%) = Discharge capacity at 60 °C / Discharge capacity at 25 °C × 100%; The above tests are repeated three times and the average value is taken. The test results are shown in Table 1. It can be seen from the data in Table 1 that compared with Comparative Examples 1-2, the emulsions of the battery anode ceramic slurries prepared in Examples 1-4 have better dispersion stability. When this emulsion is coated on the anode substrate, it not only maintains a good coating effect, but also has excellent peel force and flexibility. In addition, the resistivity and high-temperature capacity retention rate of the anode sheet have also been greatly improved. It can be seen from the data in Example 1 and Comparative Examples 1-2 that the modified sodium carboxymethylcellulose and styrene-butadiene emulsion prepared by the present invention can synergistically enhance the efficiency and significantly improve the comprehensive performance of the ceramic slurry emulsion.

[0069] Table 1 Test Results of Emulsion Related Properties of Anode Ceramic Slurry for New Energy Vehicles

[0070]

[0071] Although the embodiments of the present application have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present application. The scope of the present application is defined by the appended claims and their equivalents.

Claims

1. An emulsion of anode ceramic slurry for a new energy vehicle battery, characterized in that: The method comprises the following raw materials in parts by weight: 80-90 parts of graphite powder, 7-13 parts of alumina powder, 1-3 parts of styrene-butadiene emulsion, and 0.4-0.7 parts of modified sodium carboxymethyl cellulose; The styrene-butadiene emulsion comprises the following raw materials in parts by weight: 25-35 parts of styrene, 20-25 parts of butadiene, 1-3 parts of acrylic acid, 0.5-1 parts of itaconic acid, 0.2-0.5 parts of tert-dodecyl mercaptan, 0.4-0.6 parts of sodium dodecylbenzene sulfonate, 0.5-2 parts of sodium alkylphenol polyoxyethylene ether sulfate, 1-2 parts of acrylamide, 0.4-1 parts of sodium persulfate, 0.1-1 parts of solid alkali, 0.1-0.2 parts of liquid alkali, 40-50 parts of water, 0.5-1.0 parts of defoaming agent, and 0.5-1.0 parts of preservative; The preparation method of the modified sodium carboxymethyl cellulose is: S1. Disperse methyl oleate in anhydrous ethanol under nitrogen atmosphere and stirring, add ethanolamine, mix well, and then dropwise add sodium methoxide methanol solution. The addition is completed within 0.5-1.5 hours, and the temperature is raised to 40-60° C., react for 6-8 hours, and then cool and purify to obtain an intermediate; S2. Disperse 2,5-dimethylhexanoic acid in N,N-dimethylformamide under stirring, add the intermediate obtained in step S1 and p-toluenesulfonic acid, raise the temperature to 75-95° C., react for 6-10 hours, and obtain modified oleic acid ester by cooling and purification; S3, dispersing sodium carboxymethyl cellulose in deionized water, stirring at 55-65°C until dissolved, cooling to room temperature, and then dropping potassium persulfate aqueous solution, the dropping is completed in 40-60 minutes, and stirring is continued for 10-20 minutes, and then adding the modified oleic acid ester obtained in step S2, heating to 70-90°C, stirring and reacting for 2-4 hours, cooling and purifying to obtain modified sodium carboxymethyl cellulose; In step S3, the mass ratio of sodium carboxymethyl cellulose to modified oleate is 1:0.5-0.8, the amount of sodium carboxymethyl cellulose added to the deionized water is 0.08-0.11 g / mL, the volume ratio of the deionized water to the potassium persulfate aqueous solution is 10:0.3-0.5, and the molar concentration of the potassium persulfate aqueous solution is 0.09-0.11 mol / L.

2. The emulsion of the negative electrode ceramic slurry for the battery for new energy vehicles according to claim 1, characterized in that: In step S1, the mass ratio of methyl oleate to ethanolamine is 10-15:4, the amount of methyl oleate added to the anhydrous ethanol is 0.15-0.20 g / mL, the volume ratio of anhydrous ethanol to the sodium methoxide methanol solution is 40:5-10, and the molar concentration of the sodium methoxide methanol solution is 3.5-4.5 mol / L.

3. The emulsion of the negative electrode ceramic slurry for the battery for new energy vehicles according to claim 1, characterized in that: The mass ratio of 2,5-dimethylhexanoic acid, intermediate and p-toluenesulfonic acid in step S2 is 2-3:5:0.08-0.12, and the amount of 2,5-dimethylhexanoic acid added to N,N-dimethylformamide is 0.18-0.26 g / mL.

4. The emulsion of the negative electrode ceramic slurry for the battery for new energy vehicles according to claim 1, characterized in that: The defoaming agent is polydimethylsiloxane.

5. The emulsion of the negative electrode ceramic slurry for the battery for new energy vehicles according to claim 1, characterized in that: The preservative is one or more of phenoxyethanol, ethylhexylglycerin and p-hydroxybenzoic acid.

6. The emulsion of the negative electrode ceramic slurry for the battery for new energy vehicles according to claim 1, characterized in that: The preparation method of the styrene-butadiene emulsion is: (1) Adding acrylic acid, solid alkali and part of sodium dodecylbenzene sulfonate to part of water, stirring until dissolved, to obtain an aqueous phase; (2) adding tert-dodecyl mercaptan to part of styrene and stirring for 20-40 minutes to obtain an oil phase; (3) Under stirring conditions, add sodium alkylphenol polyoxyethylene ether sulfate, acrylamide, itaconic acid, part of butadiene, remaining sodium dodecylbenzene sulfonate and remaining styrene to the remaining water, and after vacuuming, heat to 75-80°C, add part of sodium persulfate, and react at 93-97°C for 20-40 minutes, then add water phase, oil phase, remaining sodium persulfate and remaining butadiene, and keep warm at 95-100°C for 0.5-1.5 hours, and finally add liquid alkali, defoaming agent and preservative, mix well, filter and discharge to obtain the product.

7. The method for preparing an emulsion of anode ceramic slurry for a new energy vehicle battery according to any one of claims 1 to 6, characterized in that: The following steps are involved: Disperse modified sodium carboxymethyl cellulose in deionized water, stir at 60-70°C until dissolved, cool to room temperature, add styrene-butadiene emulsion, stir for 15-25 minutes to obtain a mixed emulsion; mechanically solid-phase mix graphite powder and alumina powder to obtain a mixed powder; add the mixed emulsion to the mixed powder, stir for 40-60 minutes, grind, sieve and remove bubbles in vacuum to obtain the product.

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