Hyperbranched polymer dispersant and preparation method thereof, positive electrode slurry and lithium ion battery

Abstract

The invention provides a hyperbranched polymer dispersant and a preparation method thereof, positive electrode slurry and a lithium ion battery, and relates to the field of lithium ion batteries. The preparation method of the hyperbranched polymer dispersant comprises the following steps: mixing trimethylolpropane, cyclic ester, an end-capping reagent and a first catalyst, and carrying out polymerization reaction to obtain a hyperbranched main chain; mixing the hyperbranched main chain with alkylene oxide containing double bonds, a second catalyst and a first solvent, and performing activation reaction to obtain an activated main chain; and sequentially connecting the activated main chain with an anchoring segment, a steric hindrance segment and a conductive segment to obtain the hyperbranched polymer dispersant. According to the hyperbranched polymer dispersing agent, the anchoring section, the steric hindrance section and the conductive section are sequentially connected to the activated main chain, so that the obtained hyperbranched polymer dispersing agent has an excellent viscosity reduction effect and an excellent pole piece resistivity reduction effect, and the electrochemical performance of a battery is improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and more particularly to a hyperbranched polymer dispersant and its preparation method, a positive electrode slurry, and a lithium-ion battery. Background Technology

[0002] As lithium-ion batteries develop towards higher energy density (≥350Wh / kg), the solid content of electrode slurries is gradually increasing to 63%~72%, and the positive and negative electrode material systems are also diversifying. Against this backdrop, dispersants need to simultaneously meet two core requirements: low viscosity processability and low electrical resistance. The former determines the slurry coating efficiency and coating uniformity, while the latter directly affects the battery's fast charging and cycle performance. However, existing dispersants struggle to balance these two requirements, becoming a key bottleneck restricting the industrialization of batteries. The main problems include: 1. Limited Functionality: Existing dispersants present a contradiction: "viscosity reduction and conductivity are mutually exclusive." Existing dispersants may reduce viscosity but result in high resistance, or they may sacrifice viscosity reduction to achieve conductivity. Traditional dispersants primarily address the dispersion stability of the slurry, and their molecular structure design does not consider the impact on the electrochemical performance of the electrode. For example, Chinese patent CN119133454A discloses a polymer dispersant that, while effectively reducing slurry viscosity, its insulating polymer backbone may hinder electron transport in the electrode, leading to increased sheet resistance and consequently affecting the battery's rate performance and capacity.

[0003] 2. Lack of synergistic effect: A single dispersion mechanism (such as relying solely on steric hindrance) has limited effectiveness in complex multi-component electrode slurry systems, making it difficult to simultaneously achieve both the slurry's processing performance and the final performance of the electrode. Chinese patent CN118507730 A discloses a compound dispersant composition that can reduce slurry viscosity and electrode resistivity; however, the compound system relies on the synergistic effect of its components, making it difficult to balance viscosity reduction, stability, and resistivity reduction performance.

[0004] Therefore, there is an urgent need to develop a dispersant that can simultaneously reduce viscosity and resistivity. Summary of the Invention

[0005] The purpose of this application is to provide a hyperbranched polymer dispersant and its preparation method, a positive electrode slurry, and a lithium-ion battery to solve the above-mentioned problems.

[0006] To achieve the above objectives, this application adopts the following technical solution: A method for preparing a hyperbranched polymer dispersant, comprising: Trimethylolpropane, cyclic ester, end-capping agent and first catalyst are mixed and polymerized to obtain hyperbranched backbone; The hyperbranched backbone is mixed with an epoxide containing double bonds, a second catalyst, and a first solvent to carry out an activation reaction, thereby obtaining an activated backbone. The activated backbone is mixed with styrene monomer, acid anhydride monomer and initiator, and the anchoring section is polymerized to obtain the activated backbone with the anchoring section attached. The activated main chain of the anchoring section is mixed with hydroxyethyl methacrylate and subjected to steric hindrance polymerization to obtain the activated main chain of the anchoring section. The activated main chain of the steric hindrance segment is mixed with 3-hexylthiophene, 1,4-phenyldiboronic acid and an oxidant to carry out a conductive segment polymerization reaction to obtain a hyperbranched polymer dispersant.

[0007] According to embodiments of this application, the cyclic ester includes ε-caprolactone; And / or, the capping agent comprises polyethylene glycol monomethyl ether; And / or, the first catalyst is Sn(Oct)2; And / or, the mass ratio of the trimethylolpropane to the cyclic ester and the capping agent is (1-1.6):(9-20):(0.1-0.8); And / or, the mass of the first catalyst accounts for 0.1%-1% of the total mass of the trimethylolpropane, the cyclic ester, and the capping agent; And / or, the polymerization reaction is carried out under inert gas protection, the polymerization temperature is 75-120°C, and the polymerization time is 3-10 hours.

[0008] According to an embodiment of this application, the first solvent comprises DMF; And / or, the second catalyst comprises triethylamine; And / or, the double-bonded epoxides include glycidyl methacrylate; And / or, the activation reaction temperature is 60-100℃, and the activation reaction time is 2-6h; And / or, the molar ratio of the trimethylolpropane to the double-bonded epoxide is (0.5-1):(1.8-4). And / or, the molar ratio of the double-bonded epoxide to the second catalyst is (6-12):(0.5-2).

[0009] According to embodiments of this application, the acid anhydride monomer includes maleic anhydride, and the styrene monomer includes dodecylstyrene; And / or, the initiator includes AIBN; And / or, the molar ratio of the double-bonded epoxide to the styrene monomer is (0.8-2):(0.2-0.8). And / or, the temperature of the polymerization reaction in the anchoring section is 55-80℃, and the time of the polymerization reaction in the anchoring section is 4-8h; And / or, the molar ratio of the styrene monomer to the acid anhydride monomer and the initiator is (0.8-1.2):(0.8-1.2):(0.01-0.1).

[0010] According to an embodiment of this application, the molar ratio of the styrene monomer to the hydroxyethyl methacrylate is (0.5-1.1):(1-4). And / or, the temperature of the steric hindrance polymerization reaction is 70-90°C, and the time of the steric hindrance polymerization reaction is 3-6 hours. According to an embodiment of this application, the molar ratio of 1,4-phenyldiboronic acid to 3-hexylthiophene is 1:(6-20). And / or, the oxidant includes FeCl3; And / or, the molar ratio of the 3-hexylthiophene to the oxidant is 1:(0.01-0.1). And / or, the molar ratio of the hydroxyethyl methacrylate to the 3-hexylthiophene is 1:(0.17-0.34). And / or, the temperature of the polymerization reaction of the conductive segment is 75-100℃, and the time of the polymerization reaction of the conductive segment is 3-4h.

[0011] According to an embodiment of this application, the hyperbranched polymer dispersant is prepared by the hyperbranched polymer dispersant preparation method described above.

[0012] This application also provides a positive electrode slurry, including the hyperbranched polymer dispersant described above.

[0013] According to embodiments of this application, the content of the dispersant in the positive electrode slurry is 0.1-0.2 wt%; And / or, the positive electrode slurry further includes a conductive agent, the content of which in the positive electrode slurry is 1-1.4 wt%.

[0014] This application also provides a lithium-ion battery, including the positive electrode slurry described above.

[0015] Compared with the prior art, the beneficial effects of this application include: The dispersant of this application simultaneously reduces viscosity and resistivity. By sequentially attaching anchoring segments, steric hindrance segments, and conductive segments to the activated main chain, the hyperbranched polymer dispersant obtained in this application exhibits excellent viscosity-reducing and electrode resistivity-reducing effects. This dispersant can efficiently disperse solid components in electrode slurries, significantly reduce slurry viscosity, is suitable for high-solids-content processing, and can also participate in the construction of the electrode's conductive network, effectively reducing the electrode's surface resistance.

[0016] Specifically, the dispersant of this application has an anchoring section, a steric hindrance section, and a conductive section. The anchoring section can firmly bind the dispersant to the particles in the electrode slurry, which is beneficial to improving the dispersion performance of the dispersant. The steric hindrance section provides strong spatial repulsion force, ensuring the long-term stability and low viscosity of the slurry. The conductive section can reduce resistivity, realizing the synergy of dispersion and conductivity.

[0017] In addition, the preparation method of the dispersant of this application has the advantages of inexpensive and readily available raw materials, mild reaction conditions, and simple operation, and has good prospects for industrialization.

[0018] Since the dispersant in this application has the effect of reducing resistance, when the dispersant is used in the positive electrode slurry, the amount of conductive agent in the positive electrode slurry can be reduced, which can save production costs and avoid the adverse problem of increased viscosity caused by excessive addition of conductive agent. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly described below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation on the scope of this application.

[0020] Figure 1 This is a synthetic route diagram of the hyperbranched main chain in Embodiment 1 of this application; Figure 2 This is a synthetic route diagram for activating the main chain in Example 1 of this application; Figure 3 This is a synthetic route diagram of the activated main chain of the anchoring section in Embodiment 1 of this application; Figure 4 This is a synthetic route diagram of the activated main chain of the steric hindrance segment in Embodiment 1 of this application; Figure 5 This is a synthetic route diagram of the activated main chain for the attached conductive segment in Embodiment 1 of this application. Detailed Implementation

[0021] As used in this article: "Prepared from" is synonymous with "comprising". The terms "comprising", "including", "having", "containing", or any other variations thereof as used herein are intended to cover non-exclusive inclusion. For example, a composition, step, method, article, or apparatus that includes the listed elements is not necessarily limited to those elements, but may include other elements not expressly listed or elements inherent to such composition, step, method, article, or apparatus.

[0022] The conjunction "composed of..." excludes any unspecified elements, steps, or components. If used in a claim, this phrase makes the claim closed, excluding materials other than those described, except for associated conventional impurities. When the phrase "composed of..." appears in a clause of the body of a claim rather than immediately following it, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0023] When a quantity, concentration, or other value or parameter is expressed as a range, a preferred range, or a range defined by a series of upper and lower preferred values, this should be understood as specifically disclosing all ranges formed by any pair of any upper or preferred value with any lower or preferred value, regardless of whether the range is disclosed individually. For example, when the range “1–5” is disclosed, the described range should be interpreted as including ranges “1–4”, “1–3”, “1–2”, “1–2 and 4–5”, “1–3 and 5”, etc. When numerical ranges are described herein, unless otherwise stated, the range is intended to include its endpoints and all integers and fractions within that range.

[0024] In these embodiments, unless otherwise specified, the portions and percentages are all by weight.

[0025] "Parts by mass" refers to the basic unit of measurement that expresses the mass ratio of multiple components. One part can represent any unit mass, such as 1g or 2.689g. If we say that component A has "a" parts by mass and component B has "b" parts by mass, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it can mean that the mass of component A is aK and the mass of component B is bK (where K is any number representing a multiplier). It is important to understand that, unlike parts by mass, the sum of the mass parts of all components is not limited to 100 parts.

[0026] "And / or" is used to indicate that one or both of the described situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0027] A method for preparing a hyperbranched polymer dispersant, comprising: Trimethylolpropane, cyclic ester, end-capping agent and first catalyst are mixed and polymerized to obtain hyperbranched backbone; The hyperbranched backbone is mixed with an epoxide containing double bonds, a second catalyst, and a first solvent to carry out an activation reaction, thereby obtaining an activated backbone. The activated backbone is mixed with styrene monomer, acid anhydride monomer and initiator, and the anchoring section is polymerized to obtain the activated backbone with the anchoring section attached. The activated main chain of the anchoring section is mixed with hydroxyethyl methacrylate and subjected to steric hindrance polymerization to obtain the activated main chain of the anchoring section. The activated main chain of the steric hindrance segment is mixed with 3-hexylthiophene, 1,4-phenyldiboronic acid and an oxidant to carry out a conductive segment polymerization reaction to obtain a hyperbranched polymer dispersant.

[0028] The polymer prepared in this application simultaneously possesses anchoring, steric hindrance, and conductive segments. The anchoring segments contain strongly polar or ionizable groups, which can be firmly adsorbed onto the surface of active materials and conductive agent particles through van der Waals forces, hydrogen bonds, or ionic bonds, effectively dispersing the solid components in the electrode slurry. The steric hindrance segments have a large spatial volume effect, creating physical barriers between particles, preventing particle proximity and agglomeration, and thus improving the stability of the dispersant. The raw materials forming the conductive segments are conductive, thereby making the conductive segments conductive as well, providing additional pathways for electron transport and reducing electrode resistance.

[0029] In high-solids-content electrode slurry systems, traditional dispersants generally suffer from poor viscosity-reducing effects. To achieve a coatable viscosity, a large amount of solvent is often required, resulting in a low solids content in the slurry. This leads to low coating and drying efficiency, increased energy consumption, and the potential for migration and re-agglomeration of active materials during electrode film formation. This affects the uniformity of the electrode structure and the overall performance of the battery, ultimately deteriorating its electrochemical performance. The dispersant presented in this application exhibits excellent viscosity-reducing effects and is suitable for high-solids-content electrode slurry systems.

[0030] The dispersant of this application exhibits excellent viscosity-reducing effects, maintaining a remarkable viscosity-reducing effect even when added at a low content in the cathode slurry. Furthermore, the dispersant of this application is suitable for preparing slurries with a high solids content of 63% to 72%, which is beneficial for improving production efficiency, reducing energy consumption, and further enhancing the electrochemical performance of the battery.

[0031] According to embodiments of this application, the cyclic ester includes ε-caprolactone; And / or, the capping agent comprises polyethylene glycol monomethyl ether; And / or, the first catalyst is Sn(Oct)2 (stannous octoate); And / or, the mass ratio of the trimethylolpropane to the cyclic ester and the capping agent is (1-1.6):(9-20):(0.1-0.8); For example, the mass ratio of trimethylolpropane to cyclic ester and capping agent is any value between 1:9:0.1, 1:20:0.8, 1:19:0.5, 1.3:19:0.5, 1.6:19:0.5, 1.6:20:0.8 or (1-1.6):(9-20):(0.1-0.8).

[0032] And / or, the mass of the first catalyst accounts for 0.1%-1% of the total mass of the trimethylolpropane, the cyclic ester, and the capping agent; For example, the mass of the first catalyst is any value between 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1%, or 0.1%-1% of the total mass of trimethylolpropane, cyclic ester, and capping agent.

[0033] And / or, the polymerization reaction is carried out under inert gas protection, the polymerization temperature is 75-120°C, and the polymerization time is 3-10 hours.

[0034] For example, the polymerization temperature is any value between 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 105℃, 110℃, 115℃, 120℃ or 75-120℃, and the polymerization time is any value between 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h or 3-10h.

[0035] According to an embodiment of this application, the first solvent comprises DMF; And / or, the second catalyst comprises triethylamine; And / or, the double-bonded epoxides include glycidyl methacrylate; And / or, the activation reaction temperature is 60-100℃, and the activation reaction time is 2-6h; for example, the activation reaction temperature is any value between 60℃, 65℃, 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃ or 60-100℃, and the activation reaction time is any value between 2h, 3h, 4h, 5h, 6h or 2-6h.

[0036] And / or, the molar ratio of the trimethylolpropane to the double-bonded epoxide is (0.5-1):(1.8-4); for example, the molar ratio of the trimethylolpropane to the double-bonded epoxide is any value between 0.5:1.8, 0.5:2.8, 0.5:4, 1:1.8, 1:2.8, 1:4 or (0.5-1):(1.8-4).

[0037] And / or, the molar ratio of the double-bonded epoxide to the second catalyst is (6-12):(0.5-2). For example, the molar ratio of the double-bonded epoxide to the second catalyst is any value between 6:0.5, 10.6:0.5, 12:0.5, 6:1, 10.6:1, 12:1, 6:2, 10.6:2, 12:2, or (6-12):(0.5-2).

[0038] Through activation reactions, double-bonded epoxides can be introduced into the ends of hyperbranched main chains to obtain activated main chains, which can then serve as prepolymers that can be further grafted.

[0039] According to embodiments of this application, the acid anhydride monomer includes maleic anhydride, and the styrene monomer includes dodecylstyrene; And / or, the initiator includes AIBN; And / or, the molar ratio of the double-bonded epoxide to the styrene monomer is (0.8-2):(0.2-0.8); for example, the molar ratio of the double-bonded epoxide to the styrene monomer is any value between 0.8:0.2, 1:0.2, 2:0.2, 0.8:0.4, 1:0.4, 2:0.4, 0.8:0.6, 1:0.6, 2:0.6, 0.8:0.8, 1:0.8, 2:0.8 or (0.8-2):(0.2-0.8).

[0040] And / or, the temperature of the anchoring section polymerization reaction is 55-80°C, and the time of the anchoring section polymerization reaction is 4-8h; for example, the temperature of the anchoring section polymerization reaction is any value between 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 55-80°C, and the time of the anchoring section polymerization reaction is any value between 4h, 5h, 6h, 7h, 8h or 4-8h.

[0041] And / or, the molar ratio of the styrene monomer to the acid anhydride monomer and the initiator is (0.8-1.2):(0.8-1.2):(0.01-0.1). For example, the molar ratio of styrene monomer to anhydride monomer and initiator can be any value between 0.8:0.8:0.01, 1:0.8:0.01, 1.2:0.8:0.01, 0.8:1:0.01, 1:1:0.01, 1.2:1:0.01, 0.8:1.2:0.01, 1:1.2:0.01, 1.2:1.2:0.01, 0.8:0.8:0.04, 1:0.8:0.04, 1.2:0.8:0.04, 0.8:1:0.04, 1:1:0.04, 1.2:1:0.04, 1.2:1.2:0.04, 1.2:1.2:0.1, or (0.8-1.2):(0.8-1.2):(0.01-0.1).

[0042] According to embodiments of this application, the molar ratio of the styrene monomer to the hydroxyethyl methacrylate is (0.5-1.1):(1-4); for example, the molar ratio of the styrene monomer to the hydroxyethyl methacrylate is any value between 0.5:1, 1:1, 1.1:1, 0.5:2, 1:2, 1.1:2, 0.5:3, 1:3, 1.1:3, 0.5:3.4, 1:3.4, 1.1:3.4, 0.5:4, 1:4, 1.1:4 or (0.5-1.1):(1-4). And / or, the temperature of the steric hindrance polymerization reaction is 70-90°C, and the time of the steric hindrance polymerization reaction is 3-6 hours. For example, the temperature of the steric hindrance polymerization reaction is any value between 70°C, 75°C, 80°C, 85°C, 90°C, or 70-90°C, and the time of the steric hindrance polymerization reaction is any value between 3 hours, 4 hours, 5 hours, 6 hours, or 3-6 hours.

[0043] According to embodiments of this application, the molar ratio of 1,4-phenyldiboronic acid to 3-hexylthiophene is 1:(6-20); for example, the molar ratio of 1,4-phenyldiboronic acid to 3-hexylthiophene is any value between 1:6, 1:7, 1:8, 1:9, 1:10, 1:11, 1:12, 1:13, 1:14, 1:15, 1:16, 1:17, 1:18, 1:19, 1:20 or 1:(6-20).

[0044] And / or, the oxidant includes FeCl3; And / or, the molar ratio of the 3-hexylthiophene to the oxidant is 1:(0.01-0.1); for example, the molar ratio of the 3-hexylthiophene to the oxidant is any value between 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.06, 1:0.07, 1:0.08, 1:0.09, 1:0.1 or 1:(0.01-0.1).

[0045] And / or, the molar ratio of hydroxyethyl methacrylate to 3-hexylthiophene is 1:(0.17-0.34); for example, the molar ratio of hydroxyethyl methacrylate to 3-hexylthiophene is any value between 1:0.17, 1:0.2, 1:0.34 or 1:(0.17-0.34).

[0046] And / or, the temperature of the conductive segment polymerization reaction is 75-100°C, and the time of the conductive segment polymerization reaction is 3-4 hours. For example, the temperature of the conductive segment polymerization reaction is any value between 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, or 75-100°C, and the time of the conductive segment polymerization reaction is any value between 3 hours, 4 hours, or 3-4 hours.

[0047] In some embodiments, after the conductive segment polymerization reaction is completed, the preparation method further includes: precipitating, filtering and drying the reaction product obtained from the conductive segment polymerization reaction in a poor solvent to obtain the hyperbranched ternary structure dispersant.

[0048] For example, undesirable solvents include petroleum ether.

[0049] This application also provides a hyperbranched polymer dispersant, which is prepared by the preparation method of the hyperbranched polymer dispersant described above.

[0050] This application also provides a positive electrode slurry, including the hyperbranched polymer dispersant described above.

[0051] According to embodiments of this application, the content of the dispersant in the positive electrode slurry is 0.1-0.2 wt%; for example, the content of the dispersant in the positive electrode slurry is 0.1 wt%, 0.11 wt%, 0.12 wt%, 0.13 wt%, 0.14 wt%, 0.15 wt%, 0.16 wt%, 0.17 wt%, 0.18 wt%, 0.19 wt%, 0.2 wt%, or any value between 0.1-0.2 wt%.

[0052] The positive electrode slurry also includes a conductive agent, the content of which is 1-1.4 wt%. For example, the content of the conductive agent in the positive electrode slurry is 1 wt%, 1.1 wt%, 1.2 wt%, 1.3 wt%, 1.4 wt%, or any value between 1 and 1.4 wt%.

[0053] The conductive agent content in existing cathode slurries is typically above 2 wt%, and the addition of conductive agent will cause the viscosity of the cathode slurry to increase. Compared with existing cathode slurries, adding the dispersant of this application to the cathode slurry can significantly reduce the amount of conductive agent used while maintaining the conductivity of the cathode slurry.

[0054] In some embodiments, the conductive agent includes at least one of conductive carbon black and conductive carbon nanotubes.

[0055] In some embodiments, the positive electrode slurry further includes a positive electrode active material, a binder, and a second solvent.

[0056] Furthermore, the second solvent includes NMP, the positive electrode active material includes lithium iron phosphate, and the binder includes polyvinylidene fluoride.

[0057] In some embodiments, the mass ratio of the positive electrode active material to the conductive carbon black, conductive carbon nanotubes, dispersant, and binder in the positive electrode slurry is 93~97:0.5~0.7:0.5~0.7:0.1~0.2:2.

[0058] This application also provides a lithium-ion battery, including the positive electrode slurry described above.

[0059] The implementation schemes of this application will be described in detail below with reference to specific embodiments. However, those skilled in the art will understand that the following embodiments are only for illustrating this application and should not be regarded as limiting the scope of this application. Unless otherwise specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments used without specified manufacturers are all conventional products that can be purchased commercially.

[0060] The raw material information for the following examples and comparative examples is shown in Table 1 below.

[0061] Table 1. Raw material information for the examples and comparative examples.

[0062] I. Preparation of Dispersants Example 1 Example 1 provides a hyperbranched polymer dispersant, the preparation method of which includes: (1) Preparation of hyperbranched backbone: refer to Figure 1 Add the following to a dry 500 mL four-necked flask: TMP (5.0 g, 0.037 mol), MPEG (20.0 g, 0.02 mol), and ε-caprolactone (CL, 80.0 g, 0.699 mol), and purge with nitrogen three times. Heat to 110℃, add Sn(Oct)2 (0.5 g, 0.0012 mol, accounting for 0.5% of the total monomer mass), stir at 300 rpm, and keep the reaction at this temperature for 8 h; Cool to 60°C, add DMF (100 mL) to dilute, and obtain a hyperbranched polyether ester backbone solution (molecular weight 2000~5000).

[0063] (2) Main chain end group activation: refer to Figure 2 Add glycidyl methacrylate (GMA, 15.0 g, 0.105 mol) to the main chain solution from the first step, and heat to 80°C; Triethylamine (TEA) (1.0 g, 0.0099 mol) was added, and the reaction was maintained at this temperature for 4 h. The methacrylate double bond was introduced through the ring-opening reaction of the epoxy group and the main chain hydroxyl group. Unreacted GMA was removed by vacuum distillation to obtain the activated hyperbranched backbone.

[0064] (3) Step-by-step grafting of three functional segments: a. Anchoring section splicing steps refer to Figure 3The reaction system includes an activated main chain solution (100 g) and DMF (50 mL), and the reaction system is heated to 70 °C. A mixture of monomers, namely dodecylstyrene (12.0 g, 0.041 mol), MAH (4.0 g, 0.041 mol), and AIBN (0.3 g, 0.0018 mol), was added to the reaction system and reacted for 6 h under nitrogen protection. b. Steps for grafting steric hindrance segments refer to Figure 4 HEMA (18.0 g, 0.138 mol) was added to the above system a, the temperature was raised to 85 °C, and the reaction was continued for 5 h; c. Conductive segment grafting steps refer to Figure 5 Add 3HT (8.0 g, 0.047 mol) and BDB (0.5 g, 0.0029 mol) to the above b system, heat to 90℃, and add FeCl3 (0.2 g, 0.0012 mol, oxidant). After a 4-hour heat treatment, 3HT forms oligothiophene chains with a degree of polymerization of 3-5 under the control of BDB, which are then grafted onto the main chain branches. (4) Purification and post-processing: Cool to room temperature, slowly add the reaction solution dropwise into 5 times its volume of petroleum ether, stir to precipitate, and filter to collect the solid; Dissolve the precipitate with DMF (50 mL), then add it dropwise to petroleum ether to recrystallize again. Repeat twice (to remove unreacted monomers and low molecular weight byproducts). Vacuum drying for 12 h yielded a pale yellow powdery dispersant with a yield of 75.6%.

[0065] GPC determined the molecular weight (Mn) of the dispersant obtained in Example 1 to be 3800.

[0066] Example 2 The dispersant was prepared according to the method of Example 1. The difference between Example 2 and Example 1 is that in step c of the conductive segment grafting in Example 2, the amount of 3HT was reduced to 4.0 g (0.0235 mol), and the other raw materials and steps were the same as in Example 1.

[0067] Example 3 The dispersant was prepared according to the method of Example 1. The difference between Example 3 and Example 1 is that in step (1) of Example 3, the amount of TMP was increased to 8.0 g (0.059 mol), and the other raw materials and steps were the same as in Example 1.

[0068] Comparative Example 1 Comparative Example 1 uses a conventional linear dispersant, specifically polypyrrolidone (PVP K30), which was purchased commercially.

[0069] Comparative Example 2 The dispersant was prepared according to the method of Example 1. The difference between Comparative Example 2 and Example 1 is that the dodecyl styrene in the anchoring section grafting step a in Comparative Example 2 was replaced with dodecyl acrylate (which has no benzene ring and cannot be stacked π-π). The other raw materials and steps were the same as in Example 1.

[0070] Comparative Example 3 The dispersant was prepared according to the method of Example 1. The difference between Comparative Example 3 and Example 1 is that TMP was not added in step (1) of Comparative Example 3, and ethylene glycol was used to replace TMP in the same molar amount. The other raw materials and steps were the same as in Example 1.

[0071] Comparative Example 4 The dispersant was prepared according to the method of Example 1. The difference between Comparative Example 4 and Example 1 is that Comparative Example 4 omits the anchoring segment grafting step a, and directly performs steric hindrance segment grafting step b on the product of step (2). Everything else is the same as Example 1.

[0072] The dispersant prepared in Comparative Example 4 does not contain an anchoring segment, but only a steric hindrance segment and a conductive segment.

[0073] Comparative Example 5 The dispersant was prepared according to the method of Example 1. The difference between Comparative Example 5 and Example 1 is that Comparative Example 5 omits the conductive segment grafting step c, while Comparative Example 4 directly performs the purification and post-treatment of the product completed by the steric hindrance segment grafting step b. The rest is the same as Example 1.

[0074] The dispersant prepared in Comparative Example 5 does not contain conductive segments, but only steric hindrance segments and anchoring segments.

[0075] Comparative Example 6 The dispersant was prepared according to the method of Example 1. The difference between Comparative Example 6 and Example 1 is that Comparative Example 5 omits the steric hindrance grafting step b, while Comparative Example 4 directly performs the conductive segment grafting step c on the product completed in the anchoring segment grafting step a. Everything else is the same as in Example 1.

[0076] The dispersant prepared in Comparative Example 6 does not contain steric hindrance segments, but only anchoring and conductive segments.

[0077] Comparative Example 7 Comparative Example 7 used commercially available dispersant PVP K30 as the dispersant.

[0078] II. Performance Testing The dispersants prepared in Examples 1-3 and Comparative Examples 1-7 were used to formulate positive electrode slurries.

[0079] In Examples 1-3 and Comparative Examples 1-6, the mass ratio of positive electrode active material to conductive carbon black, conductive carbon nanotubes, dispersant, and binder was 96.8:0.5:0.5:0.2:2. In Examples 1-3 and Comparative Examples 1-6, the amount of conductive agent accounted for 1 wt% of the positive electrode slurry.

[0080] Compared with Examples 1-3 and Comparative Examples 1-6, Comparative Example 7 increases the amount of conductive agent. In Comparative Example 7, the amount of conductive agent accounts for 2 wt% of the positive electrode slurry. Specifically, in Comparative Example 7, the mass ratio of positive electrode active material to conductive carbon black, conductive carbon nanotubes, dispersant, and binder is 95.8:1:1:0.2:2.

[0081] Weigh the positive electrode active material, conductive carbon black, conductive carbon nanotubes, dispersant, and binder according to the above content relationship. The positive electrode active material is lithium iron phosphate, the binder is polyvinylidene fluoride, the solvent is N-methylpyrrolidone, and the slurry solid content is 68%-72% (when the initial viscosity of the slurry is too high, subsequent processing cannot be carried out. To facilitate processing, the solid content is reduced by adding a solvent).

[0082] (1) The adhesive is dissolved in the solvent by high-speed stirring to prepare white glue; (2) Add conductive carbon black, conductive carbon nanotube slurry (purchased, the solid content of conductive carbon nanotube slurry is 5%), and the dispersant of the example or comparative example to white glue and stir evenly to prepare black glue. (3) Add the positive electrode active material to the black glue and stir at high speed to obtain the positive electrode slurry.

[0083] The slurry testing method is as follows: 1. The viscosity of the slurry was tested using a digital rotor viscometer, L4 rotor, for 30 seconds, and the viscosity was recorded at 30 rpm.

[0084] Because the initial viscosity of the slurries in Comparative Examples 1-4 and 6-7 was too high, subsequent processing steps could not be performed. To facilitate processing, solvents were added to the slurries in Comparative Examples 1-4 and 6-7 to reduce the solid content.

[0085] 2. Electrode resistivity testing was performed using a four-probe tester, and the electrode areal density was controlled at 240 g / m² on one side. 2 about.

[0086] Battery assembly: 18650 cylindrical battery, capacity 1500mAh. The positive electrode is a lithium iron phosphate electrode containing the dispersant of the examples or comparative examples, the negative electrode is a graphite electrode, the electrolyte is 1 mol / L LiPF6-EC / DEC / DMC=1:1:1 (volume ratio), and the separator is a polypropylene porous membrane with a thickness of 20 μm.

[0087] Battery testing: The Xinwei CT-4008-5V10A battery testing system was used. The test procedure is as follows: The battery was charged and discharged at a current of 0.5C for 500 cycles. It was then charged to the upper limit voltage of 3.7V, with a cutoff current of 0.01C, left to rest for 5 minutes, and then discharged to the lower limit voltage of 2.0V.

[0088] Table 2 Test results of Examples 1-3 and Comparative Examples 1-7

[0089] Wherein, 0h viscosity refers to the viscosity of the freshly prepared positive electrode slurry, 48h viscosity refers to the viscosity of the prepared positive electrode slurry after standing at room temperature for 48 hours, and viscosity growth rate = (48h viscosity - 0h viscosity) / 0h viscosity × 100%.

[0090] As can be seen from Table 2, the hyperbranched polymer dispersants of Examples 1-3 simultaneously exhibit excellent dispersion stability (low initial viscosity, low viscosity growth rate), good electronic conductivity (low resistivity), and significant cycle durability, with their overall effect being significantly better than that of Comparative Examples 1-7.

[0091] Compared with Example 1, the electrode resistance of Example 2 is higher, which may be due to the reduced amount of conductive segments in the preparation method of Example 2, resulting in an incomplete electron conduction network.

[0092] Compared with Example 1, the dispersion performance, tack stabilization performance and electrical resistance performance of Example 3 were all reduced. This may be due to the excessive branching of Example 3, which led to a decrease in the solubility of the dispersant.

[0093] The poor dispersion stability of Comparative Example 2 may be due to the lack of π-π interaction provided by the benzene ring structure in the dispersant prepared in Comparative Example 2, which relies solely on hydrophobic interaction for anchoring, resulting in insufficient anchoring force.

[0094] The slurry stability of Comparative Example 3 is poor, which may be because the dispersant prepared in Comparative Example 3 adopts a linear main chain structure. The linear main chain cannot provide effective steric hindrance, and the particles are prone to agglomeration.

[0095] The slurry in Comparative Example 4 had a high initial viscosity, poor adhesion stabilization, and high electrode resistivity. This may be because the dispersant prepared in Comparative Example 4 did not contain an anchoring section, resulting in poor adsorption of lithium iron phosphate particles and an inability to effectively reduce viscosity. The electrode resistivity of Comparative Example 5 is high. This may be because the dispersant prepared in Comparative Example 5 does not contain conductive segments, and the dispersant cannot form an effective conductive network.

[0096] The adhesion stabilization effect of Comparative Example 6 is poor. This may be because the dispersant prepared in Comparative Example 6 does not contain steric hindrance segments, and cannot provide effective steric hindrance, resulting in rapid aggregation of dispersed particles.

[0097] Comparative Example 7 used a conventional dispersant with a higher amount of conductive agent. Examples 1 and 3 used the dispersant of this application, and the amount of conductive agent in them was less than that in Comparative Example 7. The electrode resistivity of Comparative Example 7 was higher than that of Examples 1 and 3. This shows that using the dispersant of this application can still reduce resistivity even with a reduced amount of conductive agent. Moreover, the viscosity growth rate of Comparative Example 7 was higher than that of Examples 1-3, and the cycle retention rate was worse than that of Examples 1-3. The overall performance of Comparative Example 7 was inferior to that of Examples 1-3. As shown in Table 2, at a relatively high solid content of around 72%, the initial viscosity of the cathode slurry using the dispersant of this application can be stably controlled at 10000 mPa. Below s, compared to using the traditional linear dispersant PVP (Comparative Example 1) at a solid content of around 67%, the pressure is greater than 15000 mPa. Regarding the initial viscosity of s, this application achieves a significant reduction in viscosity at higher solid content, which is beneficial for high-speed and uniform coating of high solid content slurries.

[0098] Furthermore, the cathode slurry formulated with the dispersant of this application exhibits excellent storage stability. After standing at room temperature for 48 hours, the viscosity fluctuation range of the slurry can be controlled within ±50% of the initial value, with no significant post-thickening phenomenon. In contrast, traditional dispersants show a larger viscosity increase after 48 hours under the same conditions, leading to slurry spoilage. This application can effectively extend the usable time of the slurry.

[0099] The electrode prepared using the dispersant of Example 1 has a resistivity that is reduced by about 72% compared to the electrode using the conventional PVP dispersant (Comparative Example 1), and exhibits superior electrochemical performance.

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

[0101] Furthermore, those skilled in the art will understand that although some embodiments herein include certain features included in other embodiments but not others, combinations of features from different embodiments are intended to be within the scope of this application and form different embodiments. For example, in the foregoing claims, any of the claimed embodiments can be used in any combination. The information disclosed in this background section is intended only to enhance the understanding of the general background of this application and should not be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

Claims

1. A method for preparing a hyperbranched polymer dispersant, characterized in that, include: Trimethylolpropane, cyclic ester, end-capping agent and first catalyst are mixed and polymerized to obtain hyperbranched backbone; The hyperbranched backbone is mixed with an epoxide containing double bonds, a second catalyst, and a first solvent to carry out an activation reaction, thereby obtaining an activated backbone. The activated backbone is mixed with styrene monomer, acid anhydride monomer and initiator, and the anchoring section is polymerized to obtain the activated backbone with the anchoring section attached. The activated main chain of the anchoring section is mixed with hydroxyethyl methacrylate and subjected to steric hindrance polymerization to obtain the activated main chain of the anchoring section. The activated main chain of the steric hindrance segment is mixed with 3-hexylthiophene, 1,4-phenyldiboronic acid and an oxidant to carry out a conductive segment polymerization reaction to obtain a hyperbranched polymer dispersant.

2. The method for preparing the hyperbranched polymer dispersant according to claim 1, characterized in that, The cyclic esters include ε-caprolactone; And / or, the capping agent comprises polyethylene glycol monomethyl ether; And / or, the first catalyst is Sn(Oct)2; And / or, the mass ratio of the trimethylolpropane to the cyclic ester and the capping agent is (1-1.6):(9-20):(0.1-0.8); And / or, the mass of the first catalyst accounts for 0.1%-1% of the total mass of the trimethylolpropane, the cyclic ester, and the capping agent; And / or, the polymerization reaction is carried out under inert gas protection, the polymerization temperature is 75-120°C, and the polymerization time is 3-10 hours.

3. The method for preparing the hyperbranched polymer dispersant according to claim 1, characterized in that, The first solvent includes DMF; And / or, the second catalyst comprises triethylamine; And / or, the double-bonded epoxides include glycidyl methacrylate; And / or, the activation reaction temperature is 60-100℃, and the activation reaction time is 2-6h; And / or, the molar ratio of the trimethylolpropane to the double-bonded epoxide is (0.5-1):(1.8-4). And / or, the molar ratio of the double-bonded epoxide to the second catalyst is (6-12):(0.5-2).

4. The method for preparing the hyperbranched polymer dispersant according to claim 1, characterized in that, The acid anhydride monomers include maleic anhydride, and the styrene monomers include dodecyl styrene; And / or, the initiator includes AIBN; And / or, the molar ratio of the double-bonded epoxide to the styrene monomer is (0.8-2):(0.2-0.8). And / or, the temperature of the polymerization reaction in the anchoring section is 55-80℃, and the time of the polymerization reaction in the anchoring section is 4-8 h; And / or, the molar ratio of the styrene monomer to the acid anhydride monomer and the initiator is (0.8-1.2):(0.8-1.2):(0.01-0.1).

5. The method for preparing the hyperbranched polymer dispersant according to claim 1, characterized in that, The molar ratio of the styrene monomer to the hydroxyethyl methacrylate is (0.5-1.1):(1-4). And / or, the temperature of the steric hindrance polymerization reaction is 70-90℃, and the time of the steric hindrance polymerization reaction is 3-6h.

6. The method for preparing the hyperbranched polymer dispersant according to any one of claims 1-5, characterized in that, The molar ratio of 1,4-phenyldiboronic acid to 3-hexylthiophene is 1:(6-20). And / or, the oxidant includes FeCl3; And / or, the molar ratio of the 3-hexylthiophene to the oxidant is 1:(0.01-0.1). And / or, the molar ratio of the hydroxyethyl methacrylate to the 3-hexylthiophene is 1:(0.17-0.34). And / or, the temperature of the polymerization reaction of the conductive segment is 75-100℃, and the time of the polymerization reaction of the conductive segment is 3-4h.

7. A hyperbranched polymer dispersant, characterized in that, The hyperbranched polymer dispersant is prepared by the method for preparing the hyperbranched polymer dispersant according to any one of claims 1-6.

8. A positive electrode slurry, characterized in that, Includes the hyperbranched polymer dispersant as described in claim 7.

9. The positive electrode slurry according to claim 8, characterized in that, The dispersant content in the positive electrode slurry is 0.1-0.2 wt%; And / or, the positive electrode slurry further includes a conductive agent, the conductive agent being present in the positive electrode slurry at a content of 1-1.4 wt%.

10. A lithium-ion battery, characterized in that, Includes the positive electrode slurry as described in claim 8 or 9.

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