Water-based binder with high ionic conductivity and self-repairing function, preparation method of water-based binder, silicon negative electrode, battery and power-related equipment

Abstract

The invention provides a water-based binder with high ionic conductivity and a self-repairing function, a preparation method of the water-based binder, a silicon negative electrode, a battery and electric equipment, and relates to the field of batteries. The preparation method of the aqueous binder comprises the following steps: carrying out a first reaction on poly (1, 4-butylene adipate) glycol and isophorone diisocyanate under the action of a catalyst to obtain an NCO-terminated prepolymer; after cooling, adding a sulfonate-containing chain extender 2-[(2-aminoethyl) amino] ethanesulfonate into the system, and carrying out a first chain extension reaction; adding a micromolecule chain extender diethylene glycol into the system, and carrying out a secondary chain extension reaction; and adding glacial acetic acid into the system, and emulsifying and dispersing to obtain the water-based binder. According to the water-based binder provided by the invention, the peel strength is improved by 47% or above, the ionic conductivity is improved by 3-5 orders of magnitude compared with that of a traditional water-based binder PAA, and the cycle stability of a battery is excellent.

Description

Technical Field

[0001] This application relates to the field of batteries, and more particularly to an aqueous binder with high ionic conductivity and self-healing function, its preparation method, a silicon anode, a battery, and electrical equipment. Background Technology

[0002] Silicon (Si) is considered the most promising anode material for next-generation high-energy-density lithium-ion batteries due to its extremely high theoretical specific capacity. However, silicon undergoes a huge volume change (>300%) during charge and discharge, which leads to the pulverization of active materials, repeated rupture and reconstruction of the solid electrolyte interphase (SEI) film, and damage to the electrode structure, ultimately resulting in rapid capacity decay and shortened cycle life.

[0003] Binders are one of the key components in overcoming the above challenges. Currently, the main technical means to address the volume expansion of silicon anodes include: 1. Hydrogen-bonding-based adhesives: such as polyacrylic acid (PAA) and carboxymethyl cellulose (CMC), whose carboxyl groups (-COOH) or hydroxyl groups (-OH) can form hydrogen bonds with the oxide layer (SiO2) on the silicon surface, providing stronger adhesion (e.g., patent application CN114512660A). However, these adhesives generally have low electronic / ionic conductivity, and the hydrogen bond network is prone to irreversible damage under repeated volume expansion stress, making them unable to maintain stable cycling over a long period.

[0004] 2. Conductive polymer binders: such as polypyrrole and polyaniline, which have good electronic conductivity and help improve the conductive network of electrodes (e.g., patent application CN113437314A). However, their adhesion is usually weak, and they are difficult to use in aqueous processing systems. They are also not environmentally friendly and require the use of toxic solvents such as NMP.

[0005] 3. Adhesives incorporating sulfonyl groups: Patent application document (CN115411266A) discloses the incorporation of sulfonyl groups (-SO2) into non-aqueous adhesives. - This approach utilizes the strong polarity and lithium-ion transport capabilities of organic solvents. However, it remains based on organic solvent systems, failing to address environmental and cost issues, and does not incorporate dynamic self-healing capabilities.

[0006] The existing technical solutions have the following inherent contradictions: 1) Environmentally friendly water-based binders (such as PAA and CMC) have limited functions, poor ionic conductivity, and static hydrogen bond networks are prone to fatigue failure; 2) High-performance binders (such as sulfonyl polymers and conductive polymers) are mostly non-water-based systems, which pose environmental pollution, high cost, and safety risks; 3) Existing solutions mainly suppress volume expansion by "passively bearing" rather than by "actively repairing" the problem, resulting in insufficient long-term cycling stability of the electrodes. Summary of the Invention

[0007] The purpose of this application is to provide an aqueous binder with high ionic conductivity and self-healing function, a method for preparing the same, a silicon anode, a battery, and electrical equipment, in order to solve the above-mentioned problems.

[0008] To achieve the above objectives, this application adopts the following technical solution: A method for preparing an aqueous adhesive with high ionic conductivity and self-healing function, comprising: The NCO-terminated prepolymer was obtained by reacting poly(1,4-butanediol adipate) and isophorone diisocyanate in the presence of a catalyst. After cooling, 2-[(2-aminoethyl)amino]ethanesulfonate, a chain extender containing sulfonate, was added to the system to carry out the first chain extension reaction; Add diethylene glycol, a small molecule chain extender, to the system to carry out a secondary chain extension reaction; Glacial acetic acid was added to the system, and the aqueous binder was obtained by emulsification and dispersion.

[0009] Using sodium 2-[(2-aminoethyl)amino]ethanesulfonate (AAS) as a hydrophilic chain extender is an effective and specific implementation method for introducing sulfonyl groups.

[0010] Preferably, the method for preparing the water-based adhesive with high ionic conductivity and self-healing function satisfies one or more of the following conditions: (1) The mass ratio of the poly(1,4-butanediol adipate) diol to the isophorone diisocyanate is (40-60%):(40-60%). Optionally, the mass ratio of the poly(1,4-butanediol adipate) diol to the isophorone diisocyanate can be any value between 40%:60%, 50%:50%, 60%:40%, or (40-60%):(40-60%). (2) The catalyst comprises dibutyltin dilaurate, and the amount used is 0.01wt%-0.05wt% of the total mass of the water-based binder with high ionic conductivity and self-healing function; Optionally, the amount of catalyst can be any value between 0.01wt%, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, or 0.01wt%-0.05wt% of the total mass of the water-based binder with high ionic conductivity and self-healing function; (3) The temperature of the first reaction is 83-87℃ and the time is 2-3h; Optionally, the temperature of the first reaction can be any value between 83°C, 84°C, 85°C, 86°C, 87°C or 83-87°C, and the time can be any value between 2h, 2.5h, 3h or 2-3h. (4) The final temperature of the cooling process is 58-62℃; Optionally, the endpoint temperature for cooling can be any value between 58°C, 59°C, 60°C, 61°C, 62°C, or 58°C-62°C. (5) The amount of the sulfonate chain extender is 3wt%-8wt% of the total mass of the water-based adhesive with high ionic conductivity and self-healing function; Optionally, the amount of the sulfonate chain extender can be any value between 3wt%, 4wt%, 5wt%, 6wt%, 7wt%, 8wt%, or 3wt%-8wt% of the total mass of the water-based adhesive with high ionic conductivity and self-healing function. (6) During the first chain extension reaction, the pH of the system is controlled at 7-8 and the reaction time is 1-2 hours; Optionally, during the first chain extension reaction, the pH of the system is controlled at any value between 7, 7.5, 8 or 7-8, and the reaction time can be any value between 1h, 1.5h, 2h or 1-2h. (7) The amount of the small molecule chain extender is 5wt%-10wt% of the total mass of the water-based adhesive with high ionic conductivity and self-healing function; Optionally, the amount of the small molecule chain extender can be any value between 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or 5wt%-10wt% of the total mass of the water-based adhesive with high ionic conductivity and self-healing function. (8) The pH of the system after adding the glacial acetic acid is 6-7; Optionally, the pH of the system after adding the glacial acetic acid can be any value between 6, 6.5, 7, or 6-7; (9) The emulsification and dispersion are carried out using high-speed shearing at 2000-5000 rpm; Optionally, the shearing speed can be any value between 2000 rpm, 3000 rpm, 4000 rpm, 5000 rpm, or 2000-5000 rpm; (10) The solid content of the water-based adhesive is 28-32%.

[0011] Optionally, the solid content of the water-based adhesive can be any value between 28%, 29%, 30%, 31%, 32%, or 28-32%.

[0012] Preferably, the process after emulsification and dispersion further includes: Diethylamine was added to carry out a further chain extension reaction.

[0013] This application also provides an aqueous adhesive with high ionic conductivity and self-healing function, which is prepared using the method for preparing the aqueous adhesive with high ionic conductivity and self-healing function.

[0014] Preferably, the molar ratio of hydroxyl groups to sulfonate groups in the molecular chain of the water-based adhesive is (5-20):1; The molar content of hydroxyl groups (-OH) in the polymer is 5-20 times that of sulfonates (-SO3Na) to form a hydrogen bond network of sufficient density.

[0015] Optionally, the molar ratio of hydroxyl groups to sulfonate groups in the molecular chain of the water-based adhesive can be any value between 5:1, 10:1, 15:1, 20:1 or (5-20):1; the molar content of hydroxyl groups (-OH) in the polymer can be any value between 5, 10, 15, 20 or 5-20 times that of sulfonate (-SO3Na).

[0016] And / or, The weight-average molecular weight of the water-based adhesive is 150,000-350,000 g / mol.

[0017] Optionally, the weight-average molecular weight of the water-based adhesive can be any value between 150,000 g / mol, 200,000 g / mol, 250,000 g / mol, 300,000 g / mol, 350,000 g / mol, or 150,000-350,000 g / mol.

[0018] A specific molar ratio of hydroxyl to sulfonate groups (5:1 to 20:1) is key to achieving the synergistic effect of strong adhesion, high ionic conductivity and dynamic self-healing.

[0019] The weight-average molecular weight (Mw) should be controlled between 150,000 and 350,000 g / mol to balance film-forming properties, slurry viscosity and mechanical properties.

[0020] This application also provides a silicon anode, the raw material of which includes an anode slurry, said anode slurry comprising, by weight, 100% of the total mass: 70-85wt% silicon-carbon composite (can be any value between 70wt%, 75wt%, 80wt%, 85wt%, or 70-85wt%), 10-20wt% solid electrolyte (can be any value between 10wt%, 15wt%, 20wt%, or 10-20wt%), 5-10wt% binder (can be any value between 5wt%, 6wt%, 7wt%, 8wt%, 9wt%, 10wt%, or 5-10wt%), and 3-5wt% conductive agent (can be any value between 3wt%, 4wt%, 5wt%, or 3-5wt%). The adhesive is the water-based adhesive with high ionic conductivity and self-healing function.

[0021] Preferably, the silicon-carbon composite is SiC; The solid electrolyte includes Li6PS5Cl; The conductive agent includes SP and / or CNT.

[0022] This application also provides a method for preparing the silicon anode, comprising: The silicon-carbon composite, the solid electrolyte, the binder, the conductive agent, and an aqueous solvent are mixed, ball-milled, and then coated onto the surface of a current collector and dried to obtain the silicon anode.

[0023] This application also provides a battery including the aforementioned silicon negative electrode.

[0024] For example, a silicon anode is stacked with a sulfide solid electrolyte layer and a cathode layer to form an all-solid-state battery.

[0025] This application also provides an electrical device, including the aforementioned battery.

[0026] Electrical equipment can include, for example, electric vehicles, electric bicycles, and energy storage devices.

[0027] Compared with the prior art, the beneficial effects of this application include: The aqueous adhesive with high ionic conductivity and self-healing function, and its preparation method provided in this application, have the following advantages: 1. Excellent adhesion: The peel strength is increased by more than 47%. Due to the high-density hydrogen bonding, the peel strength of the electrode in this example is significantly higher than that in the comparative example, effectively inhibiting the shedding of active material. 2. High ionic conductivity: The introduction of sulfonate groups improves ionic conductivity by 3-5 orders of magnitude compared to traditional aqueous binders (PAA), which is superior to non-aqueous control samples and reduces battery polarization; 3. Excellent cycle stability: Thanks to the self-healing ability of dynamic hydrogen bonds, the battery in this embodiment can still retain more than 80% of its capacity after 100 cycles, and the buffering effect of volume expansion is significant. 4. Water-based and environmentally friendly: The entire preparation process requires no organic solvents, meeting the requirements of green manufacturing.

[0028] The waterborne adhesive with high ionic conductivity and self-healing function provided in this application and its preparation method are the first to successfully introduce sulfonate groups into a waterborne polyurethane (WPU) dispersion system, creating a waterborne adhesive with excellent adhesion, high ionic conductivity and self-healing ability. Attached Figure Description

[0029] 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.

[0030] Figure 1 This is a comparison chart of battery cycle data for the examples and comparative examples. Detailed Implementation

[0031] 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.

[0032] Example 1 This embodiment provides a water-based adhesive with high ionic conductivity and self-healing function, and the preparation method is as follows: ① Prepolymerization: In a dry reactor, add 50g of poly(1,4-butanediol adipate) diol (PBA, Mn=1000, providing flexibility and hydroxyl groups), 35g of isophorone diisocyanate (IPDI) and 0.05g of catalyst (dibutyltin dilaurate), and react for 2 hours at 85°C under nitrogen protection to obtain a -NCO-terminated prepolymer.

[0033] ② Hydrophilic chain extension (a key step in introducing sulfonyl groups): Cool the system to 60°C, add 10g of an aqueous solution (50% concentration) containing sodium 2-[(2-aminoethyl)amino]ethanesulfonate (AAS), a hydrophilic chain extender containing sulfonate, and control the pH of the system to 7-8 with 0.1mol / L NaOH solution to carry out the chain extension reaction for 1 hour, thereby incorporating the sulfonate groups into the polymer backbone.

[0034] ③ Further chain extension (introducing additional hydroxyl groups): Subsequently, 7g of diethylene glycol (DEG) was added as a small molecule chain extender to provide more hydroxyl sites and consume the remaining -NCO groups. The reaction continued until the characteristic absorption peak of the -NCO groups completely disappeared.

[0035] ④ Neutralization, emulsification and post-chain extension: Add glacial acetic acid to adjust the pH to 6-7, and add deionized water under high-speed shear at 2000 rpm for emulsification and dispersion to obtain a stable waterborne polyurethane dispersion (weight average molecular weight of 250,000 g / mol).

[0036] The S-WPU dispersion (30% solid content) synthesized using the above method was mixed evenly with deionized water at a weight ratio of silicon-carbon composite (SiC, Shenzhen BTR): conductive agent (SP): binder (S-WPU, based on solids) = 80:10:10, and then coated onto copper foil after drying to form a negative electrode sheet.

[0037] Example 2 Similar to Example 1, except that the synthesis formula was adjusted so that the amount of AAS added was 5% and the molar ratio of -OH / -SO3Na was controlled at 10:1.

[0038] Example 3 Similar to Example 2, carbon nanotubes (CNTs) accounting for 1% of the total solid mass were added during slurry preparation to synergistically construct a superior conductive network with S-WPU.

[0039] Comparative Example 1 Common polyacrylic acid (PAA) is used as a binder. The negative electrode slurry is prepared according to the silicon-carbon composite (SiO₂) formula. x The weight ratio of conductive agent (SP) to binder (PAA) is 80:10:10. The mixture is prepared by uniform mixing with deionized water and then coated onto copper foil. The mixture is then dried to form a negative electrode sheet.

[0040] Comparative Example 2 Referring to existing technology (CN111777984A), a polyimide (PI-SO2) binder containing sulfonyl groups is synthesized, requiring NMP as a solvent. The slurry preparation ratio is the same as Comparative Example 1, but the solvent is replaced with NMP.

[0041] The negative electrode sheets obtained in the examples and comparative examples were stacked and assembled with a sulfide solid electrolyte layer (LPSC) and a positive electrode layer (NCM811) to form an all-solid-state mold full cell.

[0042] The performance of the above-mentioned all-solid-state batteries was tested, and the results are shown in Table 1 below. Figure 1 As shown: Table 1 Performance Data

[0043] The concept of this invention lies in designing a water-based adhesive that integrates "strong adhesion," "high ionic conductivity," and "dynamic self-healing." The core lies in the simultaneous introduction of high-density hydroxyl (-OH) and sulfonyl (-SO3) groups into a water-based, environmentally friendly system through molecular design. - To achieve synergy among the three functions: 1. Hydroxyl groups provide strong adhesion and cohesion: A large number of hydroxyl groups form a strong hydrogen bond network with the silicon surface, providing initial strong adhesion and inhibiting the shedding of active materials.

[0044] 2. Sulfonyl groups enhance ionic conductivity and stabilize aqueous systems: The sulfonate group, as a permanent hydrophilic group, ensures excellent water solubility of the binder; simultaneously, the anions ionized from it are fixed to the polymer chain, effectively promoting lithium ionization (Li₂O₃). + ( ) Migration, reducing battery impedance.

[0045] 3. Dynamic reversible hydrogen bonds enable self-repair: A dynamic reversible hydrogen bond network can be formed between hydroxyl groups and between hydroxyl groups and sulfonyl groups. When silicon volume expansion leads to the formation of microcracks, this network can break and recombine, enabling the binder layer to self-repair and reintegrate the electrode structure, thereby achieving continuous and adaptive buffering against volume changes.

[0046] 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.

Claims

1. A method for preparing an aqueous adhesive with high ionic conductivity and self-healing function, characterized in that, include: The NCO-terminated prepolymer was obtained by reacting poly(1,4-butanediol adipate) and isophorone diisocyanate in the presence of a catalyst. After cooling, 2-[(2-aminoethyl)amino]ethanesulfonate, a chain extender containing sulfonate, was added to the system to carry out the first chain extension reaction; Add diethylene glycol, a small molecule chain extender, to the system to carry out a secondary chain extension reaction; Glacial acetic acid was added to the system, and the aqueous binder was obtained by emulsification and dispersion.

2. The method for preparing the water-based adhesive with high ionic conductivity and self-healing function according to claim 1, characterized in that, One or more of the following conditions must be met: (1) The mass ratio of the poly(1,4-butanediol adipate) diol to the isophorone diisocyanate is (40-60%):(40-60%). (2) The catalyst comprises dibutyltin dilaurate, and the amount used is 0.01wt%-0.05wt% of the total mass of the water-based binder with high ionic conductivity and self-healing function; (3) The temperature of the first reaction is 83-87℃ and the time is 2-3h; (4) The final temperature of the cooling process is 58-62℃; (5) The amount of the sulfonate chain extender is 3wt%-8wt% of the total mass of the water-based adhesive with high ionic conductivity and self-healing function; (6) During the first chain extension reaction, the pH of the system is controlled at 7-8 and the reaction time is 1-2 hours; (7) The amount of the small molecule chain extender is 5wt%-10wt% of the total mass of the water-based adhesive with high ionic conductivity and self-healing function; (8) The pH of the system after adding the glacial acetic acid is 6-7; (9) The emulsification and dispersion are carried out using high-speed shearing at 2000-5000 rpm; (10) The solid content of the water-based adhesive is 28-32%.

3. The method for preparing the water-based adhesive with high ionic conductivity and self-healing function according to claim 1 or 2, characterized in that, The emulsification and dispersion process further includes: Diethylamine was added to carry out a further chain extension reaction.

4. A water-based adhesive with high ionic conductivity and self-healing function, characterized in that, It is prepared using the method for preparing the water-based adhesive with high ionic conductivity and self-healing function according to any one of claims 1-3.

5. The water-based adhesive with high ionic conductivity and self-healing function according to claim 4, characterized in that, The molar ratio of hydroxyl groups to sulfonate groups in the molecular chain of the water-based adhesive is (5-20):1; And / or, The weight-average molecular weight of the water-based adhesive is 150,000-350,000 g / mol.

6. A silicon anode, characterized in that, Its raw materials include negative electrode slurry, which, calculated by total mass of 100%, includes: 70-85wt% silicon-carbon composite, 10-20wt% solid electrolyte, 5-10wt% binder and 3-5wt% conductive agent; The adhesive is the water-based adhesive with high ionic conductivity and self-healing function as described in claim 4 or 5.

7. The silicon anode according to claim 6, characterized in that, The silicon-carbon composite is SiC; The solid electrolyte includes Li6PS5Cl; The conductive agent includes SP and / or CNT.

8. A method for preparing a silicon anode as described in claim 6 or 7, characterized in that, include: The silicon-carbon composite, the solid electrolyte, the binder, the conductive agent, and an aqueous solvent are mixed, ball-milled, and then coated onto the surface of a current collector and dried to obtain the silicon anode.

9. A battery, characterized in that, Includes the silicon anode as described in claim 6 or 7.

10. An electrical-related device, characterized in that, Includes the battery as described in claim 9.

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