Dispersing agent, preparation method of dispersing agent, negative electrode slurry and application of negative electrode slurry

Abstract

The invention discloses a dispersing agent and a preparation method thereof as well as negative electrode slurry and application thereof, and relates to the technical field of dispersing agents. The dispersing agent disclosed by the invention is prepared from the following components: a styrene-N-vinyl pyrrolidone-vinylamine segmented copolymer and poly (methacrylic acid polyethylene glycol ester) laurate; the mass ratio of the styrene-N-vinyl pyrrolidone vinyl amine segmented copolymer to the poly (methacrylic acid polyethylene glycol ester) laurate is (3 to 6): 1. The steric hindrance effect of the styrene-N-vinyl pyrrolidone-vinylamine block copolymer and the dynamic wettability of the poly (methacrylic acid polyethylene glycol ester) laurate cooperate with each other, the dispersing and wetting effects are achieved at the same time, the dispersing performance is remarkably improved, and the obtained dispersing agent is suitable for being used in negative electrode slurry and can be used as a negative electrode material. The dispersion stability of the sizing material is improved.

Description

Technical Field

[0001] This invention relates to the field of dispersant technology, and in particular to a dispersant and its preparation method, a negative electrode slurry and its application. Background Technology

[0002] With the development of new energy vehicles and energy storage industries, the lithium-ion battery industry continues to face the core demands of high performance, high stability, and low-cost manufacturing. In the anode manufacturing process, the preparation of aqueous slurries using carbon-based materials such as graphite is a core technology. Its dispersion uniformity and long-term stability directly determine the coating quality, electrode performance, and even the final battery's energy density, rate capability, and cycle life. However, graphite materials have a large specific surface area and strong hydrophobicity, making them prone to severe agglomeration and sedimentation in aqueous environments due to van der Waals forces. This leads to a sharp increase in slurry viscosity, deterioration of rheological properties, and limited solid content, resulting in coating defects, uneven electrode resistance, and battery performance degradation. Currently widely used traditional dispersants, such as sodium carboxymethyl cellulose (CMC) and polyacrylic acid (PAA), while improving wettability to some extent, face problems such as insufficient dispersion efficiency, poor storage stability of the dispersed slurry leading to easy water separation and sedimentation, and the introduction of excessive insulating polymers that damage the electrode conductive network and increase interfacial impedance. Therefore, developing dispersants that combine dispersibility and wettability, excellent dispersion efficiency, and the ability to improve slurry stability and electrode electrical properties has become a key technological challenge for promoting the performance and cost advantages of lithium-ion battery electrodes, and has significant industrial application value. Summary of the Invention

[0003] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, the object of the present invention is to provide a dispersant that, through the steric hindrance effect of styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and the dynamic wetting properties of poly(polyethylene glycol methacrylate) laurate, simultaneously achieves dispersion and wetting effects, significantly improving dispersion performance.

[0004] A second aspect of the present invention is to provide a method for preparing a dispersant.

[0005] A third aspect of the present invention is to provide a negative electrode slurry.

[0006] A fourth aspect of the present invention is to provide a negative electrode.

[0007] A fifth aspect of the present invention is to provide a lithium-ion battery.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: A first aspect of the present invention is to provide a dispersant comprising a styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and poly(polyethylene glycol methacrylate) laurate; wherein the mass ratio of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer to the poly(polyethylene glycol methacrylate) laurate is (3~6):1.

[0009] The dispersant of this invention contains a styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and poly(polyethylene glycol methacrylate) laurate. The styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, as the main dispersant, is an amphiphilic block polymer containing hydrophobic segments (polystyrene segments) and hydrophilic segments (polyvinylamine segments). It can effectively adsorb onto the surface of particles in the slurry, forming a steric hindrance effect, preventing particle agglomeration, and improving dispersibility and dispersion stability. The poly(polyethylene glycol methacrylate) laurate, as an auxiliary dispersant, can reduce the surface tension of the slurry, promote wetting contact between the negative electrode material and the solvent, shorten the dispersion time, improve the wettability of the dispersion, and assist the main dispersant in improving particle deagglomeration efficiency, thus improving dispersion efficiency. This invention overcomes the limitations of traditional single-mechanism dispersants by combining the steric hindrance effect of styrene-N-vinylpyrrolidone-ethyleneamine block copolymer with the dynamic wetting synergy of poly(polyethylene glycol methacrylate) laurate. It achieves both wetting and dispersion effects, significantly improving the dispersion performance of the dispersant, especially the dispersion efficiency and dispersion stability (i.e., the stability of the dispersed slurry).

[0010] It should be understood that the dispersant provided in the first aspect of the present invention can be in the form of a solid powder or a micelle solution; wherein the number average particle size of the solid powder of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer is ≤50μm, and the number average particle size of the solid powder of poly(polyethylene glycol methacrylate) laurate is 20~100μm; when the two are dispersed in water to form a micelle solution, the number average particle size of the micelle particles formed by the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer is 40~50nm, and the number average particle size of the micelle particles formed by the poly(polyethylene glycol methacrylate) laurate is 20~100nm.

[0011] Preferably, in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the mass ratio of polystyrene segments to polyvinylamine segments is 1:(1~2).

[0012] More preferably, in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the mass ratio of polystyrene segments to polyvinylamine segments is 1:(1.2~1.8).

[0013] More preferably, and even more preferably, in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the mass ratio of polystyrene segments to polyvinylamine segments is 1:(1.4~1.6).

[0014] Preferably, in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the number average molecular weight of the polystyrene segments is 10,000 to 15,000.

[0015] More preferably, the number-average molecular weight of the polystyrene segments is 11,000 to 13,000.

[0016] Preferably, in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the precursor of the polyvinylamine segment is a poly(N-vinylpyrrolidone) segment; the number average molecular weight of the poly(N-vinylpyrrolidone) segment is 16,000 to 20,000. It should be understood that the poly(N-vinylpyrrolidone) segment precursor means that in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer of the present invention, the polyvinylamine segment is obtained by hydrolysis of the poly(N-vinylpyrrolidone) segment. In the present invention, a styrene prepolymer is polymerized with N-vinylpyrrolidone to obtain a styrene-N-vinylpyrrolidone copolymer, and then the styrene-N-vinylpyrrolidone copolymer is hydrolyzed, causing some of the N-vinylpyrrolidone segments to hydrolyze into ethyleneamine segments, thus obtaining the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer. The degree of hydrolysis is 40-50%.

[0017] More preferably, the number-average molecular weight of the poly(N-vinylpyrrolidone) segments is 17,000 to 19,000.

[0018] Specifically, the preparation method of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer includes the following steps: S01. Styrene, initiator and RAFT chain transfer agent are mixed and reacted to obtain styrene prepolymer; S02. The styrene prepolymer obtained in step S01 is mixed and reacted with N-vinylpyrrolidone (NVP) to obtain a styrene-N-vinylpyrrolidone block copolymer, denoted as PS-b-PNVP; S03. The PS-b-PNVP obtained in step S02 is subjected to a hydrolysis reaction to convert the poly(N-vinylpyrrolidone) segments into polyvinylamine segments, thereby obtaining the styrene-N-vinylpyrrolidone-vinylamine block copolymer.

[0019] Preferably, in step S01, the reaction temperature is 65~75℃; and the reaction time is 22~26h.

[0020] Preferably, in step S01, the initiator is azobiscyanopentanoic acid (ACVA) and / or azobisisobutyronitrile (AIBN).

[0021] Preferably, in step S01, the RAFT chain transfer agent comprises cyanodithiobenzoate (CPDB).

[0022] Preferably, in step S01, the reaction is carried out in an organic solvent; the organic solvent may be toluene.

[0023] Preferably, in step S01, the molar ratio of styrene, RAFT chain transfer agent and initiator is (180~220):1:(0.1~0.3).

[0024] Preferably, in step S02, the reaction temperature is 75~85℃; and the reaction time is 16~20h.

[0025] Preferably, in step S02, the reaction is carried out in an organic solvent, such as tetrahydrofuran (THF).

[0026] Preferably, in step S02, the mass ratio of the styrene prepolymer to the N-vinylpyrrolidone is 1:(1~2).

[0027] Preferably, in step S03, the hydrolysis reaction is carried out in a hydrochloric acid solution; the concentration of the hydrochloric acid solution is 1~2 mol / L.

[0028] Preferably, in step S03, the temperature of the hydrolysis reaction is 55~65℃; and the time of the hydrolysis reaction is 5~7h.

[0029] Preferably, the poly(polyethylene methacrylate) laurate is obtained by esterification of poly(polyethylene methacrylate) and lauric acid.

[0030] Specifically, the preparation method of the poly(polyethylene glycol methacrylate) laurate includes the following steps: S11. Poly(poly(methacrylate)) and an initiator are mixed and subjected to free radical polymerization to obtain poly(poly(methacrylate)); S12. The poly(polyethylene glycol methacrylate) obtained in step S11 is mixed with lauric acid and subjected to esterification reaction to obtain crude poly(polyethylene glycol methacrylate) laurate. S13. The crude poly(polyethylene glycol methacrylate) laurate obtained in step S12 is purified to obtain poly(polyethylene glycol methacrylate) laurate.

[0031] Preferably, the reaction temperature of the free radical polymerization reaction in step S11 is 60~70℃; the reaction time is 10~14h.

[0032] Preferably, in step S11, the molar ratio of polyethylene glycol methacrylate to initiator is (180~220):1.

[0033] More preferably, the initiator comprises azobisisobutyronitrile (AIBN) and / or azobiscyanopentanoic acid (ACVA).

[0034] Preferably, the free radical polymerization reaction in step S11 is carried out in water.

[0035] Preferably, the esterification reaction in step S12 is carried out at a temperature of 80-120°C and for a reaction time of 5-7 hours.

[0036] Preferably, the esterification reaction in step S12 is carried out in an organic solvent; the organic solvent includes toluene.

[0037] Preferably, a catalyst, such as p-toluenesulfonic acid (PTSA), is added during the esterification reaction in step S12.

[0038] Preferably, the purification in step S13 includes the following steps: removing impurities from crude poly(polyethylene glycol methacrylate) laurate by silica gel column chromatography and rotary evaporation, followed by ultrafiltration and drying to obtain the poly(polyethylene glycol methacrylate) laurate.

[0039] Preferably, the molar ratio of the hydroxyl groups in the poly(polyethylene methacrylate) to the lauric acid is 1:(1~2).

[0040] More preferably, the molar ratio of the hydroxyl groups in the poly(polyethylene methacrylate) to the lauric acid is 1:(1~1.5).

[0041] More preferably, the molar ratio of the hydroxyl groups in the poly(polyethylene methacrylate) to the lauric acid is 1:(1~1.3).

[0042] Preferably, the grafting rate of lauric acid in the poly(polyethylene methacrylate) laurate is ≥85%. Specifically, the grafting rate of lauric acid is 85-95%. More preferably, the grafting rate of lauric acid is 85-90%.

[0043] A second aspect of the present invention is to provide a method for preparing the dispersant described in the first aspect of the present invention, comprising the following steps: The styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and the poly(polyethylene glycol methacrylate) laurate are mixed to obtain the dispersant.

[0044] Preferably, the mixing is performed using a three-dimensional mixer.

[0045] Preferably, the mixing speed is 500~800 rpm; the mixing time is 20~40 min.

[0046] A third aspect of the present invention is to provide a negative electrode slurry containing the dispersant described in the first aspect of the present invention.

[0047] Preferably, the mass content of the dispersant in the negative electrode slurry is 0.5-5%.

[0048] More preferably, the mass content of the dispersant in the negative electrode slurry is 0.5-2%.

[0049] More preferably, the mass content of the dispersant in the negative electrode slurry is 1-2%.

[0050] A fourth aspect of the present invention is to provide a negative electrode, wherein the raw materials for preparing the negative electrode include the negative electrode slurry described in the third aspect of the present invention.

[0051] A fifth aspect of the present invention provides a lithium-ion battery, the lithium-ion battery comprising the negative electrode described in the fourth aspect of the present invention.

[0052] Compared with the prior art, the beneficial effects of the present invention are: 1) This invention provides a dispersant that achieves both dispersion and wetting effects by synergistically combining the steric hindrance effect of styrene-N-vinylpyrrolidone-ethyleneamine block copolymer with the dynamic wetting properties of poly(polyethylene glycol methacrylate) laurate. This significantly improves dispersion performance while also taking into account wetting properties, especially enhancing dispersion efficiency and dispersion stability. Consequently, the storage stability and wetting properties of the dispersed slurry are also improved.

[0053] 2) The dispersant of the present invention has excellent dispersibility, high dispersion efficiency and dispersion stability, and also has processing performance for negative electrode slurry. It is suitable for preparing negative electrode slurry, and the dispersibility and dispersion stability of the obtained negative electrode slurry are improved. The sedimentation rate of the slurry after 72 hours does not exceed 5%, and it has good wettability with a contact angle of less than 25°.

[0054] 3) The raw materials for preparing the negative electrode provided by this invention include the negative electrode slurry of this invention. This negative electrode slurry contains the dispersant of this invention, which improves both dispersibility and wettability. When applied to the negative electrode, it also enhances electrical performance, such as reducing interfacial impedance, increasing capacity retention, and reducing volume expansion. Therefore, this negative electrode slurry is suitable for preparing negative electrodes, especially for lithium-ion batteries. Attached Figure Description

[0055] Figure 1 This is a particle size distribution diagram of the styrene-N-vinylpyrrolidone block copolymer in Example 1.

[0056] Figure 2 The particle size change of the micelle solution of the styrene-N-vinylpyrrolidone block copolymer in Example 1 after standing for 7 days.

[0057] Figure 3 The change in solid content of the graphite negative electrode slurry prepared using the dispersant in Example 1.

[0058] Figure 4 Temperature stability of the graphite anode slurry prepared using the dispersant in Example 1.

[0059] Figure 5 The 1C capacity retention rate of the battery prepared from the graphite negative electrode slurry prepared using the dispersant in Example 1. Detailed Implementation

[0060] The present invention will be further described in detail below through specific embodiments. Unless otherwise specified, the raw materials, reagents, or apparatus used in the embodiments and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0061] The following detailed descriptions, using different embodiments and comparative examples, provide further context.

[0062] Example 1 A dispersant comprising a styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and poly(polyethylene glycol methacrylate) laurate; wherein the mass ratio of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer to the poly(polyethylene glycol methacrylate) laurate is 4:1.

[0063] In the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the mass ratio of polystyrene segments to polyvinylamine segments is 1:1.4 (calculated based on monomer units); the preparation method of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer includes the following steps: S01. 20 mmol of styrene, 0.1 mmol of RAFT chain transfer agent (cyanodithiobenzoate) and 0.02 mmol of azobisisobutyronitrile were added to toluene (mass-volume ratio of styrene to toluene was 1 g: 50 mL), nitrogen was bubbled for 30 min to remove oxygen, and the reaction was carried out in an oil bath at 70 °C for 24 h with magnetic stirring at 500 rpm during the reaction. Then, a methanol-water mixture (volume ratio of methanol to water was 4:1) was added dropwise to the obtained reaction solution, and the precipitate was separated by centrifugation to obtain styrene prepolymer (number average molecular weight 12000). S02. Take 5g of the styrene prepolymer obtained in step S01, dissolve it in tetrahydrofuran, add 7.5g of N-vinylpyrrolidone and 0.05mmol of azobisisobutyronitrile, and react at 80℃ for 18h under nitrogen protection. Then, drop the resulting reaction solution into 200mL of glacial acetic acid, precipitate, filter, and dialyze in PBS buffer at pH=7 for 24h (changing the dialysate every 4 hours). The molecular weight cutoff of the dialysis membrane is 3500Da, and a styrene-N-vinylpyrrolidone block copolymer (the number average molecular weight of the polyN-vinylpyrrolidone segments is 18000) is obtained. The styrene-N-vinylpyrrolidone block copolymer of this embodiment was dispersed in water to form a micelle solution with a concentration of 0.1 mg / mL. Dynamic light scattering (DLS) analysis revealed that the number-average particle size of the micelles was 45 ± 5 nm. Simultaneously, three batches of parallel samples of the styrene-N-vinylpyrrolidone block copolymer were prepared using the same method, and their particle size distribution and 7-day particle size change were tested. Figure 1 and Figure 2 As shown; S03. The styrene-N-vinylpyrrolidone block copolymer obtained in step S02 was dissolved in a mixture of tetrahydrofuran and 1 mol / L hydrochloric acid (the volume ratio of tetrahydrofuran to hydrochloric acid was 3:1). The mixture was refluxed at 60°C for 6 hours to partially hydrolyze the poly(N-vinylpyrrolidone) segments (degree of hydrolysis of 40-50%) into polyvinylamine segments. The polyvinylamine segments were dialyzed in PBS buffer at pH=7 (molecular weight cutoff of 3500 Da), and then freeze-dried to obtain the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer. The degree of hydrolysis was measured by potentiometric titration. The number of amine groups was determined by acid-base titration using the basicity of the ethyleneamine groups. The ratio of the number of amine groups to the number of repeating units of the poly(N-vinylpyrrolidone) segments was the degree of hydrolysis. It should be noted that, due to the ring-opening reaction that occurs during the hydrolysis of poly(N-vinylpyrrolidone) segments, the molecular structure changes, resulting in a difference between the final mass of the polyethyleneamine segment and the initial mass of the N-vinylpyrrolidone monomer. This is a reasonable stoichiometric change.

[0064] The styrene-N-vinylpyrrolidone-ethyleneamine block copolymer obtained in step S03 was dispersed in water (concentration 0.1 mg / mL), and the average micelle size was 43 ± 3 nm as determined by dynamic light scattering.

[0065] The esterification rate of lauric acid in poly(polyethylene glycol methacrylate) laurate is 85%, and the preparation method includes the following steps: S11. Dissolve 20 mmol of polyethylene glycol methacrylate (PEGMA-475) and 0.1 mmol of azobisisobutyronitrile in water, bubble with nitrogen for 15 min, and react in a water bath at 65 °C for 12 h. During the reaction, the magnetic stirring speed is 800 rpm. Then, dialyze the resulting reaction solution (molecular weight cutoff 1000 Da) and freeze-dry to obtain poly(polyethylene glycol methacrylate) (number average molecular weight 10000). S12. Take 5g of poly(polyethylene glycol methacrylate) (containing 6mmol of hydroxyl groups) obtained in step S11, 7.2mmol of lauric acid, and 0.36mmol of p-toluenesulfonic acid and dissolve them in toluene; install a water separator and reflux at 100℃ for 6h to obtain the reaction solution; S13. The reaction solution obtained in step 12 was subjected to silica gel column chromatography to remove p-toluenesulfonic acid, rotary evaporation to remove toluene, and then separated by ultrafiltration (100 kDa) and spray-dried to obtain poly(polyethylene glycol methacrylate) laurate. The chromatogram was analyzed using 1H NMR spectroscopy. 1 The esterification rate of lauric acid was determined to be 85% by ¹H NMR.

[0066] The poly(polyethylene glycol methacrylate) laurate obtained in this example was dispersed in water to form a 0.01 wt% micelle solution with a micelle size of 48 ± 3 nm.

[0067] The method for preparing the dispersant in this embodiment is as follows: A dispersant was obtained by mixing styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and poly(polyethylene glycol methacrylate) laurate in a three-dimensional mixer at a speed of 500-800 rpm for 30 min.

[0068] Example 2 A dispersant, differing from Example 1 in that: the mass ratio of polystyrene segments to polyethyleneamine segments is 1:1; the mass ratio of styrene prepolymer to N-vinylpyrrolidone in the preparation of the styrene-N-vinylpyrrolidone-vinylamine block copolymer is 1:1.15; the rest is the same as in Example 1.

[0069] Example 3 A dispersant, differing from Example 1 in that: the mass ratio of polystyrene segments to polyethyleneamine segments is 1:1.8; the mass ratio of styrene prepolymer to N-vinylpyrrolidone is 1:2 during the preparation of the styrene-N-vinylpyrrolidone-vinylamine block copolymer; the rest is the same as in Example 1.

[0070] Example 4 A dispersant, which differs from Example 1 in that: in the preparation of poly(polyethylene glycol methacrylate) laurate, the molar ratio of hydroxyl groups to lauric acid in step S12 is 1:0.8; the rest is the same as in Example 1.

[0071] Example 5 A dispersant, which differs from Example 1 in that: in the preparation of poly(polyethylene glycol methacrylate) laurate, the molar ratio of hydroxyl groups to lauric acid in step S12 is 1:1.5; the rest is the same as in Example 1.

[0072] Example 6 A dispersant differs from Example 1 in that the mass ratio of styrene-N-vinylpyrrolidone-ethyleneamine block copolymer to poly(polyethylene glycol methacrylate) laurate is 5:1; the rest is the same as in Example 1, and the dynamic surface tension of the (dispersant of the present invention) is 35.2 mN / m.

[0073] Comparative Example 1 A dispersant, differing from Example 1 in that it contains styrene-N-vinylpyrrolidone block copolymer and poly(polyethylene glycol methacrylate) laurate; that is, the hydrolysis reaction of styrene-N-vinylpyrrolidone block copolymer (step S03) is not carried out; otherwise, it is the same as Example 1.

[0074] Comparative Example 2 A dispersant, differing from Example 1 in that it contains a styrene-acrylic acid block copolymer and poly(polyethylene methacrylate) laurate; the styrene-acrylic acid copolymer is prepared by copolymerization; otherwise, it is the same as Example 1. The preparation method of styrene-acrylic acid copolymer is as follows: In the reaction vessel, deionized water and ethanol are added as solvents, and then a portion (5-10% of the total monomer mass) of acrylic acid and styrene monomers are added to form a monomer mixture. The initiator ammonium persulfate and the remaining acrylic acid and styrene monomers are pre-dissolved in a small amount of deionized water in a constant pressure dropping funnel. The monomer mass ratio of styrene to acrylic acid is 1:1.4. Stirring and heating are started to heat the reaction system to the reflux temperature of 85°C. After the temperature stabilizes, slowly add the initiator solution and the remaining monomer (90-95% of the total monomer mass) mixture; control the dropping rate and complete the addition within 3-5 hours to avoid explosive polymerization; after the addition is complete, continue to keep the reaction at reflux temperature for 2-3 hours to allow the monomer to react fully. After the reaction was complete, the system was cooled to room temperature. The solvent and unreacted monomers were removed by rotary evaporation or other methods. The resulting polymer solid was dried in a vacuum oven at 60°C to constant weight, yielding a light yellow to brown solid powder, which is the styrene-acrylic acid copolymer.

[0075] Comparative Example 3 A dispersant, differing from Example 1 in that it contains only a styrene-N-vinylpyrrolidone-ethyleneamine block copolymer; otherwise, it is the same as Example 1.

[0076] Comparative Example 4 A dispersant, specifically a commercially available PVP dispersant, wherein PVP (polyvinylpyrrolidone) has a molecular weight of 40 kDa.

[0077] Comparative Example 5 A dispersant, a conventional commercially available CMC dispersant, wherein the degree of substitution of CMC (carboxymethyl cellulose) is DS=0.7.

[0078] Test Example 1 Preparation of graphite anode slurry: The dispersants of Examples 1-5 and Comparative Examples 1-4 were used to prepare graphite anode slurry. By mass percentage, the graphite anode slurry comprised the following components: 95% graphite, 1.2% dispersant, 3% conductive carbon black, and the balance being deionized water. The preparation method is as follows: The dispersant and conductive carbon black were mixed at 500 rpm for 30 min, then graphite and deionized water were added, and the mixture was mixed at 2500 rpm and 25℃ for 1.5 h. After degassing under vacuum of -0.09 MPa for 12 min, the graphite negative electrode slurry was obtained.

[0079] The slurry is evenly coated onto the copper foil current collector, and after drying and rolling, it forms a negative electrode sheet.

[0080] Test Example 2 Preparation of silicon-based anode slurry: The dispersants from Example 6 and Comparative Example 5 were used to prepare silicon-based anode slurry.

[0081] The silicon-based anode slurry in Example 6 comprises the following components by mass percentage: 90% silicon-carbon composite (S1000 type silicon-carbon composite material, Shenzhen BTR New Energy Materials Co., Ltd.), 2% dispersant, 0.1% ammonia (5% by mass), 5% multi-walled carbon nanotubes (NC7000, Jiangsu Tiannai Technology Co., Ltd.), 0.05% leveling agent, and the balance being deionized water; its preparation method is as follows: The dispersant was mixed with ammonia water, and the pH was adjusted to 8.5. Then other components were added and mixed at 3000 rpm and 30℃ for 2 hours. Polyether-modified siloxane (BYK-333) was added as a leveling agent and mixed to obtain silicon-based negative electrode slurry.

[0082] The silicon-based anode slurry of Comparative Example 5, by mass percentage, comprises the following components: 90%, dispersant 1.5%, carbon nanotubes 5%, leveling agent 0.05%, and the balance being deionized water; its preparation method differs from that of the silicon-based anode slurry of Example 6 only in that ammonia and dispersant are not mixed.

[0083] The slurry is evenly coated onto the copper foil current collector, and after drying and rolling, it forms a negative electrode sheet.

[0084] Result detection The performance of the negative electrode slurry in the above test examples was tested using the following methods: Sedimentation rate: The sedimentation rate after standing for 72 hours was tested in accordance with GB / T 9269-2009.

[0085] Thixotropic index: Tested at 25°C using a rotational rheometer (equipped with a cone-plate clamp), the value is obtained at a shear rate of 0.1 s⁻¹. - ¹The viscosity after stabilization is similar to that at a shear rate of 10 s⁻¹ - ¹The ratio of the viscosity after stabilization.

[0086] Dynamic surface tension (mN / m): Tested at room temperature using the platinum plate method.

[0087] Initial coulombic efficiency: Tested using a CR2032 button cell. The cell structure was as follows: the negative electrode was used as the working electrode, a lithium metal sheet as the counter and reference electrode, and the electrolyte was a 1 mol / L LiPF6 solution dissolved in EC:EMC:DMC (volume ratio 1:1:1), with 10 wt% FEC film-forming additive added. The separator was a Celgard 2320 polypropylene membrane. The half-cell was assembled and cycled in an argon-protected glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). The graphite negative electrode had a charge / discharge rate of 0.1C, and the silicon-based negative electrode had a rate of 0.05C.

[0088] Capacity retention: Full cell test, graphite anode test voltage 2.5~4.2V, charge / discharge rate 5C; silicon-based anode test voltage 1.5~4.5V, charge / discharge rate 1C; 100 cycles at room temperature.

[0089] Interfacial impedance (Rct): Anode sheets were prepared using the anode slurry prepared in the test example. Half-cells assembled with lithium metal were then tested at open-circuit potential using an electrochemical workstation (test frequency 0.1~10). 5 After (Hz), the charge transfer impedance value was obtained by fitting the equivalent circuit model using ZView software.

[0090] Volumetric expansion rate: The volumetric expansion rate was calculated by analyzing the electrode cross-section using scanning electron microscopy (SEM). Specifically, fresh electrodes and electrodes after 100 charge-discharge cycles were prepared, and cross-sectional SEM images were captured. The electrode thickness (including the active material layer and the current collector) was measured at at least five different locations, and the average value was taken. The volumetric expansion rate was calculated using the following formula: Volumetric expansion rate (%) = [(Average thickness after cycles - Average thickness before cycles) / Average thickness before cycles] × 100%.

[0091] Micelle particle size: Dynamic light scattering (DLS) was used to detect the dispersant concentration in the micelle solution, which was 0.1 mg / mL.

[0092] Contact angle: The static contact angle of the paste on the copper foil surface was tested by the seat drop method at 25°C, θ=25°C.

[0093] Dispersion time: Record the time required from the start of mixing until the slurry reaches a homogeneous state.

[0094] Solid content of slurry: determined by oven drying method, dried at 105℃ to constant weight.

[0095] Temperature stability (water separation rate): After standing at 40℃ for 7 days, the percentage of the volume of the separated water phase to the total volume was measured.

[0096] The test results are shown in Tables 1-6 and Figures 3-5 The corresponding examples and comparative examples in the following test results represent the test results of the negative electrode slurry obtained with the corresponding dispersant, or the electrode and battery prepared from the negative electrode slurry.

[0097] Table 1 Comparison of test results between Example 1 and Comparative Example 4

[0098] As shown in Table 1, compared with conventional commercially available dispersants, the graphite anode slurry obtained by the dispersant of the present invention has a lower sedimentation rate and thixotropic index. The battery electrical performance prepared with the graphite anode slurry containing the dispersant of the present invention is also improved, with a first-pass coulombic efficiency as high as 95.8%, while that of Comparative Example 1 is only 89.2%. Furthermore, the capacity retention rate (5C rate) in Example 1 is 82.3%, and the interfacial impedance is only 68 Ω·cm. 2 The interface impedance of Comparative Example 1 is nearly twice that of Example 1.

[0099] Table 2 Comparison of test results between Example 6 and Comparative Example 5

[0100] As can be seen from Table 2, compared with conventional commercially available dispersants, the dispersant of the present invention produces a silicon-based negative electrode slurry with a smaller contact angle, better wettability, and a significantly higher capacity retention rate at a 5C cycling rate than Comparative Example 5. At the same time, the volume expansion rate is also smaller, only 12%, while the volume expansion rate of Comparative Example 5 is more than twice that of Example 6.

[0101] Table 3 Comparison of test results for Examples 1-3

[0102] As shown in Table 3, in the dispersant of this invention, the change in the ratio of polystyrene segments to polyethyleneamine segments in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer affects its micelle size, sedimentation rate, and the interfacial impedance of the battery prepared from the resulting graphite anode slurry. That is, it has a significant impact on dispersion performance, and thus affects the electrochemical performance of the anode. Among them, the dispersant in Example 1 has better overall performance, with the best steric hindrance and charge balance effect, the lowest interfacial impedance and sedimentation rate, and a smaller micelle size. In Example 2, the lower proportion of polyethyleneamine segments leads to decreased dispersion stability, increased micelle size, and increased sedimentation rate. In Example 3, the higher proportion of polyethyleneamine segments results in positive charge adsorption of the conductive agent in the slurry, increasing the interfacial impedance.

[0103] Table 4 Comparison of test results between Example 1 and Examples 4-5

[0104] In Table 4, the dispersant of Example 1 exhibits the best overall performance, demonstrating the best balance between dispersibility and wettability. While maintaining a contact angle of only 22°, it also reduces dynamic surface tension and dispersion time. Furthermore, the micelle solution formed by the dispersant of Example 1 shows better stability. Although Example 5 also exhibits low contact angle, dynamic surface tension, and dispersion time, demonstrating excellent wettability and dispersion efficiency, its micelle solution suffers from poor storage stability, with particle size increasing by more than 15% after 7 days of static storage. In contrast, Example 1 achieves a simultaneous improvement in both dispersion efficiency and storage stability. The dispersant of Example 4, however, exhibits poor wettability and dispersion efficiency.

[0105] Table 5 Comparison of test results between Example 1 and Comparative Examples 1-2

[0106] As shown in Table 5, the zeta potential of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer micelle solution (concentration 0.1 mg / mL, pH=6.5) in Example 1 is +25.3 ± 1.5 mV (n=3). This indicates that the micelle surface carries a moderate positive charge, which can enhance dispersion stability through electrostatic repulsion and steric hindrance effect. Compared with Comparative Examples 1 and 2, this method is more conducive to improving dispersion stability and electrochemical performance.

[0107] Table 6 Comparison of test results between Example 1 and Comparative Example 3

[0108] As shown in Table 6, compared to Example 1, Comparative Example 3, by omitting poly(polyethylene glycol methacrylate) laurate, exhibited significantly reduced wetting properties and dispersion stability, with a sedimentation rate as high as 7.9%. This demonstrates the importance of the synergistic effect of the steric hindrance effect of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and the dynamic wetting properties of poly(polyethylene glycol methacrylate) laurate in improving dispersion performance.

[0109] Figure 1 The figure shows the particle size distribution of the styrene-N-vinylpyrrolidone block copolymer in Example 1. As can be seen from the figure, the particle size of the three batches of styrene-N-vinylpyrrolidone block copolymer in Example 1 of this invention is distributed in the range of 40~55 nm.

[0110] Figure 2 The graph shows the particle size change of the styrene-N-vinylpyrrolidone block copolymer micelle solution in Example 1 after standing for 7 days. As can be seen from the graph, the particle size change of the styrene-N-vinylpyrrolidone block copolymer after 7 days of standing is small, indicating good stability of its micelle solution.

[0111] Figure 3 The change in solid content of the graphite anode slurry prepared using the dispersant in Example 1. Figure 3 The horizontal axis is in hours. Figure 3 It can be seen that the solid content of the slurry increases with the extension of storage time (1h~10h), but the overall increase is small and close to the theoretical value, indicating that its dispersion stability is better and its controllability is also better.

[0112] Figure 4 The temperature stability of the graphite anode slurry prepared using the dispersant in Example 1 is shown. It is evident that after standing at 40°C for 168 hours, the water separation rate of the slurry is only 5.7%, indicating a low water separation rate. This demonstrates that the slurry dispersed by the dispersant of this invention exhibits good temperature stability.

[0113] Figure 5 The 1C capacity retention rate of the battery prepared from the graphite anode slurry prepared using the dispersant in Example 1. From Figure 5 It can be seen that the battery prepared with this graphite anode slurry retains more than 85% of its capacity after 1000 cycles at 1C. This also demonstrates that the anode slurry obtained by the dispersant of this invention also enhances the electrochemical performance of the anode and the battery.

[0114] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A dispersant, characterized in that, The dispersant comprises styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and poly(polyethylene glycol methacrylate) laurate; the mass ratio of the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer to the poly(polyethylene glycol methacrylate) laurate is (3~6):

1.

2. The dispersant according to claim 1, characterized in that, In the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the mass ratio of polystyrene segments to polyvinylamine segments is 1:(1~2).

3. The dispersant according to claim 1 or 2, characterized in that, In the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the number average molecular weight of the polystyrene segments is 10,000 to 15,000. And / or, in the styrene-N-vinylpyrrolidone-ethyleneamine block copolymer, the precursor of the polyvinylamine segment is a poly(N-vinylpyrrolidone) segment; the number average molecular weight of the poly(N-vinylpyrrolidone) segment is 16,000 to 20,000.

4. The dispersant according to claim 1, characterized in that, The poly(polyethylene methacrylate) laurate is obtained by esterification of poly(polyethylene methacrylate) and lauric acid.

5. The dispersant according to claim 4, characterized in that, The molar ratio of the hydroxyl groups in the poly(polyethylene methacrylate) to the lauric acid is 1:(1~2). And / or, the esterification rate of the lauric acid is ≥85%.

6. A method for preparing the dispersant according to any one of claims 1 to 5, characterized in that, Includes the following steps: The styrene-N-vinylpyrrolidone-ethyleneamine block copolymer and the poly(polyethylene glycol methacrylate) laurate are mixed to obtain the dispersant.

7. A negative electrode slurry, characterized in that, The negative electrode slurry contains the dispersant according to any one of claims 1 to 5.

8. The negative electrode slurry according to claim 7, characterized in that, The mass content of the dispersant in the negative electrode slurry is 0.5-5%.

9. A negative electrode, characterized in that, The raw materials for preparing the negative electrode include the negative electrode slurry as described in claim 7.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the negative electrode as described in claim 9.

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