Functional binder, preparation method thereof and lithium ion battery

Abstract

The invention relates to the technical field of lithium ion batteries, in particular to a functional binder, a preparation method thereof and a lithium ion battery. The functional binder has a three-dimensional network structure and comprises the following raw material components: a main binder, functional polyurethane and a cross-linking agent, the functional polyurethane contains a heterocyclic group and a functional group, the heterocyclic group contains a hydrogen bond acceptor and a hydrogen bond donor, and the functional group comprises an ion-conducting group and / or an electron-conducting group; the cross-linking agent contains a hydrogen bond donor, a hydrogen bond acceptor and a positive charge group. The main binder has basic bonding performance; functional polyurethane can exert the flexibility and elasticity. The functional polyurethane and the cross-linking agent also form a hydrogen bond complementary pairing mode, so that the cross-linking agent can accurately identify heterocyclic groups on the functional polyurethane, and the bonding strength is high. And the cross-linking agent and the main binder generate an electrostatic adsorption effect. Therefore, the functional binder has relatively high flexibility, elasticity, bonding performance, lithium ion conduction and / or electron conduction performance.

Description

Technical Field

[0001] This application relates to the field of lithium-ion battery technology, and in particular to functional binders and their preparation methods, and lithium-ion batteries. Background Technology

[0002] The negative electrode of lithium-ion batteries often incorporates silicon-based materials on top of traditional active materials such as graphite to improve the energy density of the battery. However, silicon-based materials undergo significant volume expansion and contraction during charging and discharging; their conductivity is also inferior to materials like graphite; and the lithium-ion conductivity of the negative electrode needs further improvement.

[0003] Therefore, some technical solutions optimize binders. For example, some solutions introduce materials that promote lithium-ion and electron conduction into the existing binder to improve its performance, thereby enhancing the reaction kinetics of the negative electrode, increasing the ion conductivity of the SEI film, and reducing the battery's internal resistance. However, these binders still have many problems. First, the introduced materials can only function as lithium-ion and electron conductors in isolation, making it difficult to synergize with the original binder. Second, even when crosslinking agents are introduced to crosslink these materials with the original binder, the crosslinking is often random, forming a disordered three-dimensional network with significant differences in product performance, resulting in instability and difficulty in industrial mass production. Third, to ensure the effectiveness of the introduced materials, a high dosage is often required to form an electron and ion conduction network. Fourth, the introduced materials lack viscosity, flexibility, and elasticity, making it difficult for the optimized binder to accommodate the volume changes of the silicon-based material.

[0004] Therefore, existing techniques for optimizing adhesives have limited effectiveness or are insufficient to achieve multiple performance aspects, and further improvements are still needed. Summary of the Invention

[0005] The purpose of this application is to provide a functional binder and its preparation method, and a lithium-ion battery, aiming to solve the technical problem that existing negative electrode binders are not effective in optimizing ion conduction, electronic conduction and other properties.

[0006] To achieve the above-mentioned objectives, the technical solution adopted in this application is as follows: In a first aspect, this application provides a functional adhesive having a three-dimensional network structure and comprising the following raw material components: a main adhesive, a functional polyurethane, and a crosslinking agent; The main adhesive contains carboxyl groups; Functional polyurethanes contain heterocyclic groups and functional groups. The heterocyclic groups contain hydrogen bond acceptors and hydrogen bond donors, and the functional groups include ion-conducting groups and / or electron-conducting groups. Crosslinking agents contain hydrogen bond donors, hydrogen bond acceptors, and positively charged groups.

[0007] The main binder in the above raw material components refers to the binder commonly used in negative electrodes, which contains carboxyl groups to provide basic bonding properties. Functional polyurethane leverages the flexibility and elasticity of polyurethane to improve the mechanical properties of the functional binder. The functional groups also endow the functional polyurethane with strong lithium-ion conductivity and / or electronic conductivity. The crosslinking agent acts as a bridge between the main binder and the functional polyurethane: First, the heterocyclic groups in the functional polyurethane provide strong hydrogen bond acceptors and donors, and the crosslinking agent also contains hydrogen bond donors and acceptors; at least two pairs of complementary hydrogen bonds can be formed between them, similar to the pairing patterns in DNA and RNA. This not only allows the crosslinking agent to accurately recognize the heterocyclic groups on the functional polyurethane, thus binding at specific positions in the functional polyurethane to form a complementary hydrogen bond structure, but also improves the bonding strength between the two. Second, the crosslinking agent contains positively charged groups, while the carboxyl groups in the main binder are negatively charged, resulting in electrostatic adsorption between them, further enhancing the bonding strength. Therefore, these three raw material components can spontaneously assemble, and the crosslinking agent can bind to specific positions in the main binder and functional polyurethane, forming an ordered three-dimensional crosslinked network and significantly improving the bonding strength. This allows the functional polyurethane and the main binder to fully exert their synergistic effect, enhancing the modification effect. Consequently, this functional binder possesses high ion conductivity and / or electronic conductivity, adhesion, flexibility, and elasticity, which can improve the reaction kinetics of the negative electrode, increase the ion conductivity of the SEI film, and reduce the internal resistance of the battery, making it particularly suitable for negative electrode systems containing silicon-based materials.

[0008] Secondly, a method for preparing the functional adhesive described in this application includes the following steps: The functional adhesive is obtained by mixing the components, including the main adhesive, functional polyurethane and crosslinking agent.

[0009] The preparation method of this application includes the above-mentioned functional polyurethane containing heterocyclic groups and functional groups, which gives the functional polyurethane lithium-ion conductivity and / or electronic conductivity. This polyurethane is then mixed with components including a main binder and a crosslinking agent. Both the heterocyclic groups and the crosslinking agent contain hydrogen bond donors and acceptors, which can form at least two pairs of complementary hydrogen bonds, resulting in precise recognition and high bonding strength. The crosslinking agent also contains positively charged groups, which can electrostatically adsorb with the carboxyl groups in the main binder. This preparation method is process-controllable, and these components can spontaneously assemble to form an ordered three-dimensional crosslinked network. The resulting functional binder has good adhesion, flexibility, and elasticity, as well as high ion conductivity and / or electronic conductivity. It can improve the reaction kinetics of the negative electrode, increase the ion conductivity of the SEI film, and reduce the internal resistance of the battery, making it particularly suitable for negative electrode systems containing silicon-based materials.

[0010] Thirdly, this application provides a lithium-ion battery, wherein the raw material components of the negative electrode film layer of the lithium-ion battery include the functional binder described above, or include the functional binder prepared by the preparation method described above.

[0011] Because the aforementioned functional binders possess high viscosity, elasticity, flexibility, lithium-ion conductivity, and / or electronic conductivity, they can improve the reaction kinetics of the negative electrode, increase the ionic conductivity of the SEI film, and reduce the internal resistance of the battery. They are also suitable for various negative electrode active materials, especially silicon-based materials, buffering the stress impact caused by the volume expansion of silicon-based materials and stabilizing the capacity performance and charge-discharge life of the negative electrode made of silicon-based materials during battery cycling. Therefore, the negative electrode film layer of the lithium-ion battery of this application has good structural stability, is not prone to cracking or detachment, and the lithium-ion battery exhibits high cycle stability, rate performance, and lifespan. Attached Figure Description

[0012] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0013] Figure 1 This is a graph showing the ionic conductivity test results of the functional polyurethane synthesized in Example A1 of this application; Figure 2 This is a graph showing the ionic conductivity test results of the functional polyurethane synthesized in Example A2 of this application; Figure 3 This is the infrared spectrum of the functional polyurethane synthesized in Embodiment A3 of this application; Figure 4 This is a comparison chart of constant current charge-discharge tests performed on coin cells of embodiment B1 and blank group B1 in this application; Figure 5 This is a comparison chart of the constant potential electrochemical impedance spectroscopy test of coin cells in Example B2 and Blank Group B2 of this application; Figure 6 This is a comparison chart of constant current charge-discharge tests performed on coin cells of embodiment B3 and blank group B3 in this application; Figure 7 This is a comparison chart of constant current charge-discharge tests performed on coin cells of embodiment B4 and blank group B4 in this application; Figure 8 This is a comparison chart of cyclic voltammetry tests performed on button cells of embodiment B5 and blank group B5 in this application; Figure 9This is a schematic diagram illustrating the mechanism of interaction between the functional binder and the surface of the silicon-based material before the negative electrode film layer is heated. Figure 10 This is a schematic diagram illustrating the mechanism of interaction between the functional binder inside the functional binder and the surface of the silicon-based material after the negative electrode film layer is heated. Detailed Implementation

[0014] To make the technical problems, technical solutions, and beneficial effects of this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0015] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. A and B can be singular or plural. The character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0016] In this application, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or similar expressions mean any combination of these items, including any combination of single or multiple items.

[0017] It should be understood that in the various embodiments of this application, the order of the above processes does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0018] The weights of the relevant components mentioned in the embodiments of this application can refer not only to the specific content of each component, but also to the proportional relationship between the weights of the components. Therefore, any scaling up or down of the content of the relevant components according to the embodiments of this application is within the scope disclosed in the embodiments of this application. Specifically, the mass in the embodiments of this application can be a well-known unit of mass in the chemical industry, such as µg, mg, g, or kg.

[0019] The terms "first" and "second" are used for descriptive purposes only, to distinguish objects, such as substances, from one another, and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. For example, without departing from the scope of the embodiments of this application, a first feature may also be referred to as a second feature, and similarly, a second feature may also be referred to as a first feature. Thus, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0020] The first aspect of this application provides a functional adhesive having a three-dimensional network structure and comprising the following raw material components: a main adhesive, a functional polyurethane, and a crosslinking agent; The main binder contains carboxyl groups; the functional polyurethane contains heterocyclic groups and functional groups, the heterocyclic groups contain hydrogen bond acceptors and hydrogen bond donors, and the functional groups include ion-conducting groups and / or electronic groups; the crosslinking agent contains hydrogen bond donors, hydrogen bond acceptors and positively charged groups.

[0021] The main binder in the above raw material components refers to the binder commonly used in negative electrodes, which contains carboxyl groups to provide basic bonding properties. Functional polyurethane leverages the flexibility and elasticity of polyurethane to improve the mechanical properties of the functional binder. The functional groups also endow the functional polyurethane with strong lithium-ion conductivity and / or electronic conductivity. The crosslinking agent acts as a bridge between the main binder and the functional polyurethane: First, the heterocyclic groups in the functional polyurethane provide strong hydrogen bond acceptors and donors, and the crosslinking agent also contains hydrogen bond donors and acceptors; at least two pairs of complementary hydrogen bonds can be formed between them, similar to the pairing patterns in DNA and RNA. This not only allows the crosslinking agent to accurately recognize the heterocyclic groups on the functional polyurethane, thus binding at specific positions in the functional polyurethane to form a complementary hydrogen bond structure, but also improves the bonding strength between the two. Second, the crosslinking agent contains positively charged groups, while the carboxyl groups in the main binder are negatively charged, resulting in electrostatic adsorption between them, further enhancing the bonding strength. Therefore, these three raw material components can spontaneously assemble, and the crosslinking agent can bind to specific positions in the main binder and functional polyurethane, forming an ordered three-dimensional crosslinked network and significantly improving the bonding strength. This allows the functional polyurethane and the main binder to fully exert their synergistic effect, enhancing the modification effect. Consequently, this functional binder possesses high ion conductivity and / or electronic conductivity, adhesion, flexibility, and elasticity, which can improve the reaction kinetics of the negative electrode, increase the ion conductivity of the SEI film, and reduce the internal resistance of the battery, making it particularly suitable for negative electrode systems containing silicon-based materials.

[0022] Regarding the main adhesive: The carboxyl groups in the primary binder have strong hydrogen bonding effects, resulting in strong adhesion to both the negative electrode active material and the current collector. Optionally, the primary binder includes a carboxyl-containing polymer binder, which also possesses elasticity, flexibility, self-healing properties, and water-processability, making it a commonly used negative electrode binder. In some embodiments, the primary binder may include at least one of polyacrylic acid (PAA) and its salts, and the salts may include at least one of lithium, sodium, potassium, magnesium, zinc, or calcium salts. These binders are suitable for negative electrode material systems, where formulation into salt-based binders can balance solubility, processing performance, and stability in aqueous slurries. In an exemplary example, the primary binder includes not only at least one of polyacrylic acid and its salts, but also at least one of carboxymethyl cellulose and its salts, alginate and its salts, polyacrylamide and its salts, polyacrylonitrile, and guar gum and its salts. Carboxymethyl cellulose and alginate are rich in carboxyl groups, which can synergistically enhance the adhesion and electrostatic adsorption with crosslinking agents in conjunction with polyacrylic acid and its salts. Other materials can also synergistically enhance the adhesion in conjunction with polyacrylic acid and its salts.

[0023] In some embodiments, the mass percentage of carboxyl groups in the main binder is 20% to 80%, and may include, but is not limited to, any value or any two of 20%, 40%, 50%, 60%, and 80%, which can be determined by nuclear magnetic resonance spectroscopy (NMR). In some embodiments, the weight-average molecular weight of the main binder is 100,000 to 3,000,000, and may include, but is not limited to, any value or any two of 100,000, 500,000, 1,000,000, 2,000,000, and 3,000,000. These main binders with varying carboxyl group contents or molecular weights can balance properties such as adhesion, stability of the formulated negative electrode slurry, flexibility, and elasticity.

[0024] Regarding functional polyurethane: Polyurethane often possesses flexibility and elasticity. This functional polyurethane can improve the mechanical properties of functional adhesives, such as better adapting to the volume expansion of silicon-based materials. Furthermore, functional polyurethane contains heterocyclic groups, which can be integrated into the main molecular chain of the functional polyurethane, function as part of a side chain, be directly grafted onto the main chain, or a combination of these. These heterocyclic groups exhibit strong hydrogen bonding interactions and contain hydrogen bond acceptors and donors. They can form at least two pairs of strong complementary hydrogen bonds with the hydrogen bond donors and acceptors in the crosslinking agent, respectively. That is, the functional polyurethane and the crosslinking agent each use their own hydrogen bond donors to correspond to the other's hydrogen bond acceptors, or vice versa, achieving a specific recognition mechanism similar to two-point and three-point hydrogen bond recognition in DNA and RNA base pairing.

[0025] Based on this, crosslinking agents are generally small molecules, and a single crosslinking agent molecule typically only crosslinks in one region of the functional polyurethane molecule. Therefore, by designing the distribution region of heterocyclic groups within the functional polyurethane molecular chain, the region where the crosslinking agent binds within the functional polyurethane molecular chain can be precisely controlled, achieving ordered self-assembly between the functional polyurethane and the crosslinking agent. Furthermore, this complementary interaction of two or more pairs of hydrogen bonds also results in high bonding strength, significantly improving the stability of the formed crosslinked structure.

[0026] In some embodiments, the number of hydrogen bond acceptors in the heterocyclic group is equal to the number of hydrogen bond donors in the crosslinking agent, and the number of hydrogen bond donors in the heterocyclic group is equal to the number of hydrogen bond acceptors in the crosslinking agent. This matching method further facilitates precise hydrogen bond complementarity pairing between the functional polyurethane and the crosslinking agent, improving the specificity and accuracy of recognition. In an exemplary embodiment, the heterocyclic group and the crosslinking agent may each contain one hydrogen bond donor and one acceptor group, forming two pairs of complementary hydrogen bonds, mimicking the two-point hydrogen bond recognition pattern in DNA; in another exemplary embodiment, three pairs of complementary hydrogen bonds may be formed, mimicking the three-point hydrogen bond recognition pattern in DNA. If three or more pairs of complementary hydrogen bonds are formed, the accuracy of matching can be further improved, but the spatial positional relationship between the hydrogen bond acceptors and hydrogen bond donors in the heterocyclic group and the spatial positional relationship between the hydrogen bond donors and hydrogen bond acceptors in the crosslinking agent must be matched, which places higher demands on the types of heterocyclic groups and corresponding crosslinking agents.

[0027] In some embodiments, the heterocyclic groups may include at least one of pyrimidines (characteristic groups such as pyrimidine rings will not be repeated below), pyridines, and purines. Due to the high specificity of group structures and hydrogen bonding modes in DNA and RNA, their base pairing exhibits extremely high recognition accuracy and binding stability. Their complementary pairing follows this pattern: adenine (A) pairs with thymine (T) or uracil (U) through two hydrogen bonds, and guanine (G) pairs with cytosine (C) through three hydrogen bonds. Referring to the above recognition mechanism, when the heterocyclic group includes the aforementioned types of groups, it can mimic the specific hydrogen bond recognition between bases with the crosslinking agent, further precisely anchoring the crosslinking site and improving the binding strength, thereby achieving precise recognition and orderly assembly between the functional polyurethane and the crosslinking agent.

[0028] In some embodiments, the mass percentage of heterocyclic groups in the functional polyurethane can be 2% to 15%, including but not limited to any value or any two values ​​between 2%, 5%, 8%, 12%, and 15%. This content is beneficial for the functional polyurethane to contain more heterocyclic groups, enabling complementary hydrogen bond recognition and bonding with more crosslinking agents; it also avoids excessive crosslinking at too many positions in the molecular chain, which would limit the flexibility and elasticity of the functional polyurethane. Therefore, these contents are beneficial for improving the uniformity and stability of the crosslinked structure formed in the functional adhesive.

[0029] In some embodiments, the heterocyclic group is located between the hard and soft segments of the functional polyurethane. This structure allows the crosslinking sites for hydrogen bond recognition and complementary bonding between the functional polyurethane and the crosslinking agent to be located between the hard and soft segments, reducing the crosslinking of the soft and hard segments with the external environment. This makes them less susceptible to the influence of external molecules, relatively free, and able to fully and completely exert their performance advantages, such as the deformability of the soft segments. Therefore, this structure is beneficial for the introduced functional polyurethane to exert its flexibility and elasticity, further enhancing the synergistic effect between the functional polyurethane and the main binder.

[0030] In some embodiments, the weight-average molecular weight of the functional polyurethane is 20,000 to 200,000, which may include, but is not limited to, any value or any range between two values ​​of 20,000, 50,000, 100,000, 150,000 and 200,000. These molecular weights of functional polyurethane can combine various properties such as flexibility and elasticity.

[0031] Functional polyurethanes also contain functional groups, including ion-conducting and / or electronically conductive groups, which endow them with strong lithium-ion conductivity and / or electronic conductivity. These functional groups can be incorporated into the main molecular chain of the functional polyurethane, function as part of a side chain, be directly grafted onto the main chain, or a combination of these methods.

[0032] In some embodiments, the ion-conducting groups include at least one of fluorinated aromatics, trifluoromethyl aromatics, sulfonic acids, quaternary ammonium compounds, triazoles, and imidazodium compounds. These ion-conducting groups possess high lithium-ion conductivity, significantly improving the overall lithium-ion conductivity of the binder. In the subsequently prepared battery anode, lithium-ion transport occurs not only through the traditional channel formation between the anode active material and the electrolyte impregnated within the anode film, but also through the cross-linking network of the binder forming ion transport channels throughout the entire anode film, significantly improving the kinetic performance during charge and discharge. The functional binder also participates in the formation of the SEI film, giving it high ion transport performance. Therefore, functional binders containing these ion-conducting groups can significantly improve various electrical properties of lithium-ion batteries.

[0033] In some embodiments, the conductive electronic groups include at least one of thiophene, phenol, aniline, pyrrole, furan, and indole groups; these conductive electronic groups have high electronic conductivity and can significantly improve the overall electronic conductivity rate of the binder. In the subsequently prepared battery anode, electron transport can be achieved not only through the traditional channel formation of the anode active material, conductive agent, and current collector, but also through the cross-linking network of the binder forming electron transport channels throughout the entire anode film, significantly improving the kinetic performance during charge and discharge. It also helps to reduce the internal resistance of the entire battery, especially the internal resistance of batteries made with silicon-based anode materials. Therefore, functional binders containing these conductive electronic groups can significantly improve the various electrical properties of lithium-ion batteries.

[0034] In some embodiments, the mass percentage of functional groups in polyurethane can be 1% to 15%; it can include, but is not limited to, any value or any two values ​​of 1%, 4%, 7%, 10%, and 15%. The above content is conducive to the functional groups in the functional polyurethane fully exerting their lithium-ion conduction and electronic conduction performance, while at the same time, the content is not too high and crowds out the content of heterocyclic groups, hard segments, and soft segments, so that the functional polyurethane can maintain good crosslinking performance and mechanical properties at the same time.

[0035] Regarding crosslinking agents: Crosslinking agents are used to crosslink the molecular chains of functional polyurethane with those of the main binder, enabling them to self-assemble into an ordered three-dimensional crosslinked network and exert a synergistic effect. The hydrogen bond donors and acceptors in the crosslinking agent form at least two pairs of complementary hydrogen bonds with the heterocyclic groups in the functional polyurethane, allowing for precise identification and binding to specific regions within the functional polyurethane molecule. Simultaneously, the positively charged groups in the crosslinking agent can electrostatically adsorb onto the carboxyl groups in the main binder, increasing the bonding strength. Thus, the crosslinking agent can crosslink the functional polyurethane and the main binder. In some embodiments, some positively charged groups in the crosslinking agent can also act as hydrogen bond donors; the specific role they play depends on the structure of the crosslinking agent and the structure of the heterocyclic groups.

[0036] In some embodiments, the crosslinking agent includes at least one selected from guanidinoacetic acid, guanidinourea, serine, malonamide, barbituric acid, and cyanuric acid, and may be selected from at least one selected from guanidinoacetic acid and guanidinourea. These crosslinking agents contain both hydrogen bond donors and hydrogen bond acceptors, which can recognize and bind to the functional polyurethane through complementary hydrogen bond pairing, and the binding positions are fixed. They also contain positively charged groups, which can bind to the main binder through electrostatic adsorption. While self-assembling into an ordered three-dimensional structure, they significantly improve the degree of crosslinking between the functional polyurethane and the main binder.

[0037] In some embodiments, the mass ratio of the main adhesive, functional polyurethane, and crosslinking agent is (1-30):(1-3):1, which may include, but is not limited to, any ratio or any range between two of the ratios of (1 or 5 or 10 or 20 or 30):(1 or 2 or 3):1. These ratios are conducive to efficient crosslinking between the functional polyurethane and the main adhesive, and while taking into account the processing performance and bonding performance of the adhesive system, they give full play to the advantages of the elasticity, flexibility, ion conduction and / or electronic conduction of the introduced functional polyurethane, thereby improving the overall performance of the functional adhesive.

[0038] In some embodiments, the functional adhesive contains a metal salt. In some embodiments, the metal salt may include at least one of lithium salt, sodium salt, potassium salt, magnesium salt, zinc salt, and calcium salt; in some embodiments, the metal salt may include at least one of sulfate, citrate, maleate, malonate, phytate, arginine salt, and lysine salt.

[0039] On the one hand, the introduction of metal salts can effectively regulate the acid-base environment of the system, promote cross-linking reactions, enhance the stability of hydrogen bonding and electrostatic interactions, and improve the processing performance of the prepared slurry. On the other hand, after the introduction of metal salts, the carboxyl groups in the citrate and maleate salts can interact with the negative electrode active material (such as the silanol groups on the surface of silicon-based materials), such as forming hydrogen bonds to improve the viscosity of the functional binder. Furthermore, at certain temperatures, ester groups and other chemical bonds can be formed, which can improve the bonding strength between the functional binder and the negative electrode active material during subsequent battery fabrication.

[0040] On the other hand, existing binders exert their adhesive effect in a similar way to the previous point. For example, the adhesion between carboxyl-containing polymer binders and silicon-based materials is mainly achieved through the bonding of carboxyl groups with hydroxyl groups on the silicon surface, exhibiting macroscopic adhesion. During subsequent heating, chemical bonding groups such as ester groups can be formed. However, with the introduction of metal salts, while the carboxyl groups in substances such as citrate and maleate remain adsorbed on the surface of the negative electrode active material, they can also undergo electrostatic adsorption through the positive charge of metal ions with the carboxyl groups in the main binder. Of course, metal cations and anions in the metal salt also form electrostatic adsorption. Therefore, in addition to the traditional bonding mode of the carboxyl groups of the main binder bonding to the surface groups of the negative electrode active material, a further bonding pathway can be provided: negative electrode active material - carboxyl groups of metal salts - cations in metal salts - main binder. This further improves the bonding strength between functional binders and negative electrode active materials, such as... Figure 9 , Figure 10 As shown.

[0041] In some embodiments, the functional binder contains water, has a solid content of 5% to 50%, and a pH value of 5 to 8. The functional binder of this application is suitable for aqueous systems. A functional binder solution with the above-mentioned solid content and pH value can be better used for the preparation of negative electrode slurries. It can be used with components such as negative electrode active materials to prepare slurries, exhibiting good processing performance and film-forming properties.

[0042] A second aspect of this application provides a method for preparing the functional adhesive described in the above-described embodiments, comprising the following step S10: S10. The components, including the main adhesive, functional polyurethane and crosslinking agent, are mixed to obtain the functional adhesive.

[0043] The preparation method of this application includes the above-mentioned functional polyurethane containing heterocyclic groups and functional groups, which gives the functional polyurethane lithium-ion conductivity and / or electronic conductivity. This functional polyurethane is then mixed with components including a main binder and a crosslinking agent. Both the heterocyclic groups and the crosslinking agent contain hydrogen bond donors and acceptors, which can form at least two pairs of complementary hydrogen bonds, resulting in precise recognition and high bonding strength. The crosslinking agent also contains positively charged groups, which can electrostatically adsorb with the carboxyl groups in the main binder. This preparation method is process-controllable, and these components can spontaneously assemble to form an ordered three-dimensional crosslinked network. The resulting functional binder has good adhesion, flexibility, and elasticity, as well as high ion conductivity and / or electronic conductivity. It can improve the reaction kinetics of the negative electrode, increase the ion conductivity of the SEI film, and reduce the internal resistance of the battery, making it particularly suitable for negative electrode systems containing silicon-based materials.

[0044] In step S10, a functional polyurethane containing heterocyclic groups can be synthesized first. In some embodiments, the preparation method of the functional polyurethane may include the following steps S11 to S13: S11. The raw materials, including polyols and excess polyisocyanates, are subjected to prepolymerization to obtain a first prepolymer; S12. The raw materials comprising the first prepolymer, the heterocyclic group material, and the functional group material are subjected to a first chain extension treatment to obtain the second prepolymer; S13. The raw materials, including the second prepolymer and the chain transfer agent, are subjected to a second chain extension treatment to obtain a functional polyurethane.

[0045] Step S11 involves prepolymerizing polyols and excess polyisocyanates. Hydroxyl groups and isocyanate groups undergo nucleophilic addition reactions to form urethane bonds, generating a low-molecular-weight first prepolymer containing end-capped NCO groups, providing reaction sites for subsequent steps. In step S12, the excess polyisocyanates further participate in the reaction, introducing heterocyclic and functional groups into the first prepolymer to obtain a second prepolymer. Step S13 further extends the chain segments using a chain transfer agent to obtain a functional polyurethane. Through the above preparation method, heterocyclic groups can be grafted onto the molecular chain of this functional polyurethane.

[0046] Specifically, step S11 involves a nucleophilic addition reaction between a polyol and a polyisocyanate to form a soft segment. The main function of the hydrophilic polyol is to provide multiple hydroxyl groups as reactive groups, and its weight-average molecular weight can range from 400 to 4000, with slightly higher molecular weights offering better flexibility. In some embodiments, the polyol may include hydrophilic polyols and / or hydrophobic polyols. Using hydrophilic polyols as raw materials is beneficial for improving the hydrophilicity of the subsequently prepared functional polyurethane. Hydrophilic polyols may include at least one of polyethylene glycol (PEG), polyethylene glycol monomethyl ether (MPEG), polyethylene oxide-propylene oxide copolymer (PEO-PPO, EO / PO ratio > 2:1 to ensure hydrophilicity), polytrimethylene ether glycol (PO3G), and polycarbonate glycol (PCD). Hydrophobic polyols, used as raw materials, help balance hydrophilicity and hydrophobicity, reducing the risk of swelling or dissolution in functional polyurethanes due to excessive hydrophilicity. These polyols can include at least one of polypropylene glycol (PPG), polytetrahydrofuran (PTMEG), polycaprolactone diol (PCL), polyhexyl carbonate (PCDL), polybutadiene glycol (PBD), castor oil-based polyols, and soybean oil-based polyols. The mass ratio of the hydrophilic to hydrophobic polyol can be (1.5–4):1, including but not limited to any ratio or any range between two of 1.5:1, 2:1, 3:1, and 4:1. These ratios help to produce functional polyurethanes that balance hydrophilicity and structural stability. In an example, various polyols can be mixed and thoroughly stirred before reacting with polyisocyanates.

[0047] The main function of polyisocyanates is to provide multiple isocyanate groups as reactive groups, which may include at least one of hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), butyl diisocyanate (BDI, 1,4-butanediisocyanate), pentyl diisocyanate (PDI, 1,5-pentanediisocyanate), dicyclohexylmethane 4,4'-diisocyanate (H12MDI), cyclohexane 1,3-diisocyanate (CHDI), norbornane diisocyanate (NBDI), cyclohexane 1,4-diisocyanate (1,4-CHDI), diphenylmethane 4,4'-diisocyanate (MDI), toluene diisocyanate (TDI, 2,4- / 2,6-isomer), lysine diisocyanate (LDI), and isocyanurate ring (HDI trimer). These polyisocyanate raw materials can provide multiple isocyanate groups, which can undergo addition reactions with hydroxyl groups to form the desired first prepolymer of end-capped NCO with polyols. Meanwhile, excess polyisocyanates can continue to participate in the reaction during subsequent first and second chain extension treatments.

[0048] In some embodiments, the molar ratio of polyols to polyisocyanates is 1:(0.6–2.4), and may include, but is not limited to, any ratio or any range between two of 1:0.6, 1:1, 1:1.2, 1:1.5, 1:1.8, 1:2.0, and 1:2.4. When the polyols contain both hydrophilic and hydrophobic polyols, they can be formulated at a molar ratio of 1:(1–3) for both hydrophilic and polyisocyanates. These molar ratios of polyols reacting with polyisocyanates can control the degree of prepolymerization and the length of the soft segments formed.

[0049] In some embodiments, the prepolymerization temperature can be 65°C to 85°C. In some embodiments, the raw materials for prepolymerization also include carboxyl-containing polyols and / or catalysts. The multiple hydroxyl groups in the carboxyl-containing polyol can undergo addition reactions with polyisocyanates, thereby introducing carboxyl groups into the main chain of the first prepolymer. If a neutralization treatment is subsequently performed, the carboxyl groups can generate carboxylate salts. The resulting ionic groups can improve the hydrophilicity of the subsequently produced functional polyurethane and facilitate the formation of stable micelles in water, improving its dispersion stability in water while preventing excessive hydrophilicity that could lead to swelling or dissolution. In exemplary cases, the carboxyl-containing polyol can include, but is not limited to, materials such as dimethylolpropionic acid (DMPA). The amount of carboxyl-containing polyol can be proportioned according to a mass ratio of hydrophilic polyol to carboxyl-containing polyol of (10–20):1. It can be added simultaneously and mixed evenly when various polyols are mixed to ensure uniform distribution of carboxyl groups in the prepolymer.

[0050] Catalysts can lower the activation energy of the reaction, catalyze the addition reaction of polyols and polyisocyanates, improve reaction efficiency and selectivity, reduce side reactions, and facilitate the preparation of a first prepolymer with a uniform molecular weight distribution. Catalysts can include organotin catalysts, such as dibutyltin dilaurate (DBTDL) and stannous octoate. The amount of catalyst can be formulated according to a mass ratio of polyisocyanate to catalyst of (50–200):1. This range effectively promotes the reaction to form the first prepolymer without causing the reaction to be too rapid and difficult to control due to excessive dosage. These catalysts will continue to play a catalytic role in subsequent steps S12 and S13.

[0051] The prepolymerization process in step S11 can be achieved by first thoroughly mixing polyols and carboxyl-containing polyols, then adding polyisocyanates dropwise, adding the catalyst all at once, and stirring at 400 rpm to 800 rpm for 1 to 4 hours to ensure thorough mixing and the addition reaction. Referring to step S11 above, the weight-average molecular weight of the prepolymer can be 5000 to 10000, with a uniform molecular weight distribution among the prepolymer molecules.

[0052] Step S12 is a further step of performing a second chain extension treatment on the first prepolymer and the materials containing heterocyclic groups and functional groups, so as to combine the heterocyclic groups and functional groups on the first prepolymer to achieve functional modification. In some embodiments, the materials containing heterocyclic groups may include 5-(hydroxymethyl)uracil, 6-amino-1,3-dimethyluracil, 5,6-diamino-2,4-dihydroxypyrimidine, 4,5-diamino-6-hydroxy-2-mercaptopyrimidine, 5-aminouracil, 5-hydroxyuracil, 5-(hydroxymethyl)thymidine, 5-aminothymidine, 5-aminocytosine, 5-(hydroxymethyl)cytosine, 1,3,5- At least one of the following: tris(hydroxymethyl)isocyanuric acid, 5,5-dimethylisocyanuric acid, 2-amino-4,6-dihydroxypyrimidine, 4-amino-2,6-dichloropyrimidine, 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 3,5-dichloro-2-hydroxypyridine, 5-amino-2-methylpyridine, 2,6-dihydroxypyridine, and 2,6-diaminopyridine. These heterocyclic materials contain groups, such as hydroxyl and amino groups, that can undergo nucleophilic addition reactions with polyisocyanates, forming urethane (-NHCOO-) or urea bonds (-NHCONH-), which are then bonded to the first prepolymer. Furthermore, the selected functionalized organic compounds possess unique structures that allow hydroxyl and amino groups to preferentially react with isocyanate groups during nucleophilic addition reactions, as these groups are more reactive than those on heterocyclic groups, thus minimizing their impact on the heterocyclic groups. These heterocyclic groups contain hydrogen bond donors and acceptors, and some groups (such as uracil and thymine) share a base pairing with a complementary base in DNA or RNA, enabling the final functionalized polyurethane to form precise recognition and strong bonds with the crosslinking agent.

[0053] In some embodiments, the material containing functional groups includes 3-fluoro-1,2-phenylenediamine, 5-fluoro-2,3-pyridinediamine, 3-(trifluoromethyl)-1,2-phenylenediamine, 2-amino-5-sulfonic acid phenol, N-(2-aminoethyl)-N-methylimidazolium, 4-amino-3-fluorobenzoic acid, 2,6-diaminopyridine-3-sulfonic acid, 3-amino-1-propanol sulfonic acid, N,N-dimethyl-1,3-propanediamine, 5-amino At least one of the following: 2-fluorophenol, 3-amino-1,2,4-triazole-5-carboxylic acid (the above are materials containing ion-conducting groups; the following are materials containing electron-conducting groups), 2-aminothiophene, 3-aminothiophene, 4-aminophenol, 2,5-diaminothiophene, 4-hydroxyaniline, 3-hydroxyaniline, 3-aminopyrrole, 3-aminofuran, 3,4-diaminothiophene, N-(2-aminoethyl)pyrrole, and 5-aminoindole. Referring to the bonding methods of the above-mentioned heterocyclic group-containing materials, the hydroxyl and amino groups in these functional materials can participate in nucleophilic addition reactions, thereby binding the functional groups to the first prepolymer, resulting in a functional polyurethane with lithium-ion and / or electronic conductivity. It should be noted that some of the above-mentioned functional groups are tertiary amines, which require subsequent quaternization treatment to acquire ion-conducting properties.

[0054] In some embodiments, the heterocyclic material can be added at a molar ratio of (2-10):1 between the polyisocyanate in step S11 and the heterocyclic material in step S12, including but not limited to any value or any two of 2:1, 4:1, 6:1, 8:1, and 10:1; the functional material can be added at a molar ratio of (2-15):1 between the polyisocyanate and the functional material, including but not limited to any value or any two of 2:1, 4:1, 6:1, 8:1, 10:1, 12:1, and 15:1. This ratio allows the heterocyclic and functional groups to combine as much as possible on the first prepolymer to obtain the desired second prepolymer. In the example, these materials containing heterocyclic groups and functional groups can first be dissolved in a solvent, such as N,N-dimethylformamide (DMF). This solvent has good compatibility with aqueous systems, effectively promoting uniform reaction and reducing side reactions. Then, the solution of the heterocyclic and functional group materials is added to the first prepolymer, and the mixture is stirred at a stirring rate of 400 rpm to 800 rpm for 1 to 3 hours to ensure thorough homogenization. A first chain extension treatment is then performed at a certain temperature. In some embodiments, the reaction temperature for the first chain extension treatment can be 50°C to 65°C. After the reaction is complete, a second prepolymer is obtained.

[0055] Step S13 involves adding a chain transfer agent to perform a second chain extension treatment to obtain a functional polyurethane. In some embodiments, prior to the second chain extension treatment in step S13, at least one of the following steps is included: neutralization treatment, quaternization treatment, and water dispersion treatment of the second prepolymer.

[0056] The neutralization treatment mainly neutralizes the carboxyl groups in the carboxyl-containing polyols added during the prepolymerization process in step S11, generating carboxylates. On one hand, carboxylates are ionic groups, which facilitates the formation of an aqueous dispersion. On the other hand, the pH of the reaction system can be adjusted to neutral, and the electrostatic repulsion and hydrogen bonding of the carboxylates stabilize the entire reaction system, reducing side reactions during the subsequent second-chain elongation process. Furthermore, it improves the swelling resistance of the resulting functional polyurethane, allowing it to fully utilize its flexibility and resilience. In the example, the neutralizing agent used in the neutralization treatment may include, but is not limited to, at least one of triethylamine (TEA), trimethylamine (TMA), N,N-dimethylethylamine (DMEA), tripropylamine (TPA), N-methyldiethanolamine (MDEA), diethylamine (DEA), ammonia (NH3·H2O), hydroxides (lithium, sodium, potassium, and calcium hydroxides), 2-amino-2-methyl-1-propanol (AMP), and N,N-dimethylethanolamine (DMAE). During neutralization, the neutralizing agent can be directly added to the second prepolymer mentioned above. The amount added can be adjusted according to the mass ratio of carboxyl polyol to neutralizing agent as (1-3):1, and the pH value of the entire solution system can be adjusted to 6-8.

[0057] Quaternization mainly involves a nucleophilic substitution reaction between the aforementioned tertiary amine groups and a quaternizing reagent to generate a quaternary ammonium salt, thereby imparting lithium-ion conductivity. In some embodiments, the quaternizing reagent may include at least one selected from methyl iodine, methyl chloride, methyl bromide, dimethyl carbonate, dimethyl sulfate, diethyl sulfate, iodoethane, benzyl chloride, iodomethylbenzene, diethyl carbonate, and 2-chloroethanol. The reaction temperature can be between 50°C and 85°C. In some embodiments, if the quaternized product has good water solubility, the above neutralization treatment may be omitted as appropriate.

[0058] After neutralization, an appropriate amount of deionized water can be added for water dispersion treatment, followed by stirring at 800 rpm to 1500 rpm for 1 to 2 hours to ensure uniform dispersion. This water dispersion treatment forms an aqueous dispersion, which facilitates the formation of the -COO- generated during neutralization. - The ionic groups impart good hydrophilicity to the second prepolymer, and deionized water disperses the ionized prepolymer into stable micelles, giving the subsequently prepared functional polyurethane water-based properties. Furthermore, adding water after neutralization helps reduce side reactions between the remaining polyisocyanates and water. Additionally, the combination of -COO groups... -The hydrophilic / hydrophobic balance of the ionic groups and the raw materials selected in step S11 ensures that the dispersion of the second prepolymer remains stable and has high film anti-swelling properties. On the other hand, water dispersion treatment can also improve dispersion efficiency and prevent particle aggregation, which meets the standards for industrial production of functional polyurethane.

[0059] The second chain extension process is then carried out. The main step is to add a chain transfer agent to the second prepolymer, which continues to undergo an addition reaction with the remaining polyisocyanates to increase the molecular weight of the resulting functional polyurethane and introduce hard segments to increase the chain length. The chain transfer agent can be added according to the remaining -NCO content (determined by di-n-butylamine titration) at a molar ratio of n(chain transfer agent):n(remaining -NCO) of (0.90–0.98):1.

[0060] In some embodiments, the chain transfer agent may include at least one of ethylenediamine (EDA), 1,4-butanediol (BDO), 1,6-ethylenediol (HDO), 1,3-propanediamine (PDA), 1,6-hexanediamine (HDA), isophorone diamine (IPDA), diethylenetriamine (DETA), ethylene glycol (EG), 1,3-propanediol (PDO), 1,5-pentanediol (PeDO), diethylene glycol (DEG), trimethylolpropane (TMP), 1,4-cyclohexanediol (CHDM), m-phenylenediamine (MXDA), and polyetheramine (weight average molecular weight of 200-400). On the one hand, these chain transfer agents contain hydroxyl and amino groups that can react with polyisocyanates, and each contains more than two reactive groups, which can effectively extend the molecular chain of the functional polyurethane and increase its molecular weight. On the other hand, they can also increase the proportion of hard segments (urethane, urea bonds), balance the flexibility of soft segments, regulate the ratio of the two, and improve the tensile strength, toughness, and resilience of the functional polyurethane. Furthermore, they are also beneficial to improving the chemical stability of the system. Since the remaining -NCO groups will react with water to generate amines and release carbon dioxide, and will continue to generate urea bonds, they are prone to uncontrolled crosslinking or bubble generation. The timely consumption of the remaining -NCO groups by the chain transfer agent helps to reduce the occurrence of side reactions and obtain functional polyurethane with suitable viscosity.

[0061] Steps S11 to S13 above also help to combine heterocyclic groups and functional groups between the soft and hard segments of the functional polyurethane, so that each segment can give full play to its own performance advantages, thereby improving the various properties of the functional adhesive.

[0062] Finally, the product after reaction can be dialyzed in pure water for at least 96 hours. Then, it can be rotary evaporated for 1 to 3 hours at 40℃ to 50℃ and a vacuum of 5 mbar to 10 mbar to remove some of the solvent water, resulting in a concentrated functional polyurethane dispersion with a solid content of 20% to 55%, which is convenient for storage, transportation and subsequent application.

[0063] Step S10 involves mixing the raw materials, including the main binder, functional polyurethane, and crosslinking agent. The crosslinking agent spontaneously and precisely identifies and binds to the heterocyclic groups in the functional polyurethane, allowing the crosslinking agent to bind to a predetermined position in the functional polyurethane molecule. The positively charged groups in the crosslinking agent also electrostatically adsorb to the carboxyl groups in the main binder, thereby spontaneously assembling the main binder and the functional polyurethane to form a stable and ordered three-dimensional network structure. The functional polyurethane then continuously exerts its lithium-ion conduction and / or electronic conduction properties.

[0064] In the example, the mixing process can involve first dispersing the main adhesive in water, then adding the crosslinking agent, and finally adding the functional polyurethane synthesized in steps S11 to S13. In some embodiments, the mass ratio of the main adhesive, functional polyurethane, and crosslinking agent used in the mixing process can be (1-30):(1-3):1, where the ratio includes only the effective components and excludes the solvent.

[0065] In some embodiments, the mixing process may further include the following steps S14 to S16: S14. Prepare a first solution by mixing the main binder, metal hydroxide, and water, wherein the pH value of the first solution is 5 to 8.5; S15. Prepare a second solution by mixing the first solution, crosslinking agent, and acidic raw materials. The pH value of the second solution is 5 to 7.5. S16. The second solution is formulated with functional polyurethane to form a solution containing a functional adhesive.

[0066] The addition of metal hydroxides in step S14 is primarily to neutralize the main binder and improve its solubility. When subsequently used in the anode material system, the metal ions can also form electrostatic adsorption interactions with acidic raw materials and the main binder, further enhancing the bonding strength between the functional binder and the anode active material, especially the silicon-based material, and fully utilizing the adhesiveness, elasticity, and flexibility of the functional binder. These hydroxides may include at least one of lithium, sodium, potassium, magnesium, zinc, or calcium hydroxides.

[0067] Step S15 involves adding a crosslinking agent and acidic raw materials. The types of crosslinking agents can be referenced from the relevant descriptions in the first aspect of functional binders mentioned above. The added crosslinking agent combines with the main binder through electrostatic adsorption. Acidic raw materials can include sulfuric acid, citric acid, maleic acid, malonic acid, phytic acid, arginine, and lysine. On one hand, they can further adjust the pH value of the system; on the other hand, they also form electrostatic adsorption with metal ions, helping to establish an electrostatic adsorption network in the solution system (corresponding to the relevant descriptions of metal salts in the first aspect of functional binders mentioned above, where metal ions and acidic raw materials form the aforementioned metal salts); furthermore, they can undergo esterification reactions with the hydroxyl groups on the surface of the negative electrode active material, such as silicon-based materials, during the subsequent preparation of the negative electrode. Based on the combination of the main binder and the silicon-based material, this adds another binding pathway: negative electrode active material - acidic raw material - metal cation - main binder, further improving the bonding strength between the functional binder and the negative electrode active material.

[0068] In step S16, functional polyurethane is added, allowing the crosslinking agent and functional polyurethane to accurately identify and bind through complementary hydrogen bonding. The crosslinking agent facilitates the spontaneous assembly of the functional polyurethane and the main binder, forming an ordered three-dimensional crosslinked network structure. The resulting functional binder exhibits high viscosity, flexibility, elasticity, lithium-ion conductivity, and / or electronic conductivity, which can improve the reaction kinetics of the negative electrode, increase the ionic conductivity of the SEI film, and reduce the internal resistance of the battery, making it particularly suitable for negative electrode systems containing silicon-based materials. The resulting solution can be directly used for subsequent preparation of negative electrode slurries, or, as needed, a suitable amount of water can be removed for storage and transportation.

[0069] A third aspect of this application provides a lithium-ion battery, wherein the raw material components of the negative electrode film of the lithium-ion battery include the functional binder described in the embodiments of this application, or include the functional binder prepared by the preparation method described in the embodiments of this application.

[0070] Because the aforementioned functional binders possess high viscosity, elasticity, flexibility, lithium-ion conductivity, and / or electronic conductivity, they can improve the reaction kinetics of the negative electrode, increase the ionic conductivity of the SEI film, and reduce the internal resistance of the battery. They are also suitable for various negative electrode active materials, especially silicon-based materials, and can buffer the stress impact caused by the volume expansion of silicon-based materials, stabilizing the capacity performance and charge-discharge life of the negative electrode made of silicon-based materials during battery cycling. Therefore, the negative electrode film layer of the lithium-ion battery in this application embodiment has good structural stability and is not prone to cracking or detachment, resulting in high cycle stability, rate performance, and lifespan for the lithium-ion battery.

[0071] In this embodiment, the negative electrode preparation process can be as follows: mixing the negative electrode active material, conductive agent, functional binder, and solvent to obtain a negative electrode slurry; coating the negative electrode slurry onto a current collector; and preparing the negative electrode sheet through steps such as drying, rolling, and die-cutting. Specific material types and amounts can refer to commonly used parameters for existing negative electrode sheets. The relationship between the functional binder and the silicon-based negative electrode active material can be as follows: Figure 9 , Figure 10 As shown, Figure 9 , Figure 10 X in n+ It is a metal cation. Figure 9 The image shows the state before high-temperature heating, revealing that the functional polyurethane contains functional groups with ionic and / or electronic conductivity. The crosslinking agent forms complementary hydrogen bonds with the heterocyclic groups in the functional polyurethane and also forms electrostatic adsorption with the main binder. In addition to direct bonding, the main binder can also bond to the silicon surface through an electrostatic adsorption network of carboxyl-metal cation-acid raw materials-silicon surface, further enhancing adhesion. Therefore, the various raw material components in the entire system can spontaneously assemble. Figure 10 The display shows the state after high-temperature heating, where the functional binder forms chemical bonds such as ester groups with the silicon surface, resulting in high bonding strength. Figure 9 , Figure 10 The diagram illustrates the mechanism of functional adhesives during application. The functional groups shown are for illustrative purposes only, reflecting the relationships between the components.

[0072] The following description is based on specific examples. The abbreviations of the substances in each example are detailed in the above specification. For example, PEG-2000, where PEG stands for polyethylene glycol, as mentioned above, refers to PEG products with an average molecular weight of around 2000. Such expressions in the following text can be used as a reference.

[0073] Functional polyurethane Example A1.

[0074] This embodiment provides a functional polyurethane and its preparation method. The functional polyurethane has extremely high lithium-ion conductivity. The preparation method includes the following steps S1 to S7: S1. Polyol Mixing: At 80°C, PEG-2000 (10 g), PTMEG-1000 (5 g), and DMPA (0.5 g) were added to a container at one time and stirred at 550 rpm for 1 h.

[0075] S2. Prepolymer formation: At 80°C, IPDI (4.5 g) was added dropwise at a uniform rate over 30 min, followed by DBTDL (0.05 g) in one go, and the mixture was stirred at 600 rpm for 2 h.

[0076] S3. Chain Extension: At 80°C, add 3-fluoro-1,2-phenylenediamine (containing functional groups, 1 g, dissolved in 5 mL DMF) and 5,6-diamino-2,4-dihydroxypyrimidine (containing heterocyclic groups, 1 g, dissolved in 5 mL DMF), and stir at 450 rpm for 1 h. The -F group in the functional group significantly improves lithium-ion conductivity. Due to the low reactivity of the -OH (phenolic hydroxyl group) group in the heterocyclic group, the -NH2 group preferentially reacts, with its nitrogen atom attacking the carbon atom of the -NCO group to form a urea bond, reducing the influence on the pyrimidine ring. The double-NH2 structure allows the pyrimidine to act as a bridging unit, connecting the two prepolymer chains.

[0077] S4. Neutralization: Keep at 80°C, add TEA (0.7 g) all at once, and stir at 300 rpm for 30 min until the pH is 7.0.

[0078] S5. Water dispersion: At room temperature, add 50 mL of deionized water and disperse at 1000 rpm for 1 h.

[0079] S6. Secondary chain extension: Add EDA (0.5 g) all at once at room temperature and stir at 400 rpm for 30 min.

[0080] S7. Removal and Concentration: After dialyzing in pure water for 96 h, the solution is rotary evaporated for 1 h at 40 °C and a vacuum of 10 mbar to remove some of the solvent water, resulting in a functional polyurethane aqueous solution concentrated to a solid content of 30%.

[0081] Ion conductivity test: The functional polyurethane aqueous solution prepared in step S7 was poured into a Teflon mold, then dried under vacuum at 65℃ for 12 hours, and then cured at 105℃ for 2 hours to obtain a functional polyurethane film. This film was cut into circular pieces with a diameter of 12 mm, and each piece was impregnated with 30 mL of electrolyte on both sides. These pieces were then placed in the CR2032 battery casing and gasket for potentiostatic electrochemical impedance spectroscopy (PEIS) testing. The parameters were set as follows: amplitude 10 mV, frequency 1 MHz to 100 mHz, from high frequency to low frequency. The test results are as follows. Figure 1 As shown, the ionic conductivity is calculated using the formula:

[0082] Its lithium-ion conductivity reaches 10 -3 The S / cm level demonstrates that the functional polyurethane synthesized in Example A1 has extremely high ion conductivity.

[0083] Example A2 of functional polyurethane.

[0084] This embodiment provides a functional polyurethane and its preparation method. The functional polyurethane has extremely high lithium-ion conductivity. The preparation method includes the following steps S1 to S7: S1. Polyol Mixing: At 80°C, PEG-2000 (9 g) and DMPA (1 g) were added to the container at one time and stirred at 600 rpm for 1 h.

[0085] S2. Prepolymer formation: HDI (4 g) was added dropwise at a constant rate over 40 min at 80°C, followed by DBTDL (0.05 g) in one go, and stirred at 800 rpm for 2.5 h.

[0086] S3. Chain extension: Maintaining 80°C, add 5-fluoro-2,3-pyridinediamine (containing functional group material, 1 g, dissolved in 5 mL DMF) and 4,5-diamino-6-hydroxy-2-mercaptopyrimidine (containing heterocyclic group material, 1 g, dissolved in 5 mL DMF), and stir at 500 rpm for 1 h. The -NH2 group in the heterocyclic group material reacts preferentially over -OH / -SH, reducing its influence on the pyrimidine ring. Its nitrogen atom attacks the -NCO carbon atom to form a urea bond, and the bis-NH2 introduces the pyrimidine group as a bridging unit.

[0087] S4. Quaternization: Cool to 60℃, add dimethyl sulfate (0.5 g) all at once, and stir at 500 rpm for 30 minutes. The product after reaction has good water solubility, so the neutralization step can be omitted.

[0088] S5. Water dispersion: At room temperature, add 50 mL of deionized water and disperse at 1100 rpm for 1 h.

[0089] S6. Secondary chain extension: At room temperature, add HDO (0.6 g) all at once and stir at 400 rpm for 30 min.

[0090] S7. Removal and Concentration: After dialyzing in pure water for 100 h, the solution is rotary evaporated for 1.5 h at 40 °C and a vacuum of 10 mbar to remove some of the solvent water, resulting in a functional polyurethane aqueous solution concentrated to a solid content of 35%.

[0091] Ion conductivity test: The functional polyurethane aqueous solution prepared in step S7 was poured into a Teflon mold, then dried under vacuum at 65℃ for 12 hours, and then cured at 105℃ for 2 hours to obtain a functional polyurethane membrane. This membrane was cut into 12 mm diameter circular pieces, each impregnated with 30 mL of electrolyte on both sides, and placed in a CR2032 battery casing and gasket for potentiostatic electrochemical impedance spectroscopy (PEIS) testing. The parameters were set as follows: amplitude 10 mV, frequency 1 MHz~100 mHz. The test results are shown in the figure below. Figure 2 As shown, the ionic conductivity is calculated using the formula:

[0092] Its lithium-ion conductivity reaches 10 -3 The S / cm level demonstrates that the functional polyurethane synthesized in Example A1 has extremely high ion conductivity.

[0093] Example A3 of functional polyurethane.

[0094] This embodiment provides a functional polyurethane and its preparation method. The functional polyurethane has extremely high electronic conductivity. The preparation method includes the following steps S1 to S7: S1. Polyol Mixing: At 80°C, PEG-1000 (10 g), PTMEG-1000 (5 g), and DMPA (0.5 g) were added to a container at one time and stirred at 600 rpm for 1 h.

[0095] S2. Prepolymer formation: IPDI (4.44 g) was added dropwise at a constant rate for 30 min while maintaining 80 °C. DBTDL (0.05 g) was then added in one go, and the mixture was stirred at 500 rpm for 2 h.

[0096] S3. Chain Extension: Cool to 60°C, add 3-aminothiophene (containing functional group material, 1 g, dissolved in 5 mL DMF) and 5-(hydroxymethyl)uracil (containing heterocyclic group material, 1 g, dissolved in 5 mL DMF), and stir at 450 rpm for 1.5 h. Due to the low reactivity of the -NH group (amide group of uracil) in the heterocyclic group material due to its conjugation effect, the -OH group preferentially reacts with the -NCO group, reducing the impact on the pyrimidine ring and thus binding the pyrimidine ring into the prepolymer.

[0097] S4. Neutralization: Heat to 80°C, add TEA (0.35 g) all at once, and stir at 300 rpm for 30 min until the pH is 7.0.

[0098] S5. Water dispersion: At room temperature, add 50 mL of deionized water dropwise and stir at 1000 rpm for 1 h.

[0099] S6. Secondary chain extension: Add EDA (0.5 g) all at once at room temperature and stir at 400 rpm for 30 min.

[0100] S7. Removal and Concentration: After dialyzing in pure water for 120 h, the solution is rotary evaporated for 1.5 h at 40 °C and a vacuum of 10 mbar to remove some of the solvent water, resulting in a functional polyurethane aqueous solution concentrated to a solid content of 50%.

[0101] Infrared spectroscopy test: The sample obtained in step S7 after thorough drying was subjected to infrared spectroscopy test, and the test results are as follows: Figure 3 As shown. From Figure 3 It can be seen from this that 3300 cm -1 ~3400 cm -1 : NH, OH stretching, corresponding to NH of carbamate / urea bond (IPDI +PTMEG / 3-aminothiophene / 5-(hydroxymethyl)uracil / EDA); pyrimidine cycloamide NH (5-(hydroxymethyl)uracil).

[0102] 2971 cm -1 CH stretching vibration, -CH3 asymmetric / symmetric stretching (DMPA, TEA residue); -CH2- stretching (PTMEG, IPDI cyclohexane, 5-(hydroxymethyl)uracil-CH2OH).

[0103] 2864 cm -1 :-CH2- Symmetrical stretching, corresponding to PTMEG, IPDI, BDO, and 5-(hydroxymethyl)uracil.

[0104] 1726 cm -1 : C=O (carbamate), corresponding to the -NHCOO- formed by the reaction of IPDI + PTMEG / BDO / 5-(hydroxymethyl)uracil-CH2OH.

[0105] 1677 cm -1 C=O stretching (pyrimidinamide), corresponding to C2 / C4-CONH- within the 5-(hydroxymethyl)uracil ring. 1603 cm -1 : C=N / C=C stretching (pyrimidine / thiophene ring), corresponding to 5-(hydroxymethyl)uracil pyrimidine ring C=N / C=C; 3-aminothiophene thiophene ring C=C.

[0106] 1097 cm -1 COC stretching (ether bond), corresponding to the PTMEG polyether chain -COC-.

[0107] 768 cm -1 : CS stretching (thiophene ring), corresponding to 3-aminothiophene ring CS.

[0108] This demonstrates that the synthesized functional polyurethane successfully incorporates the desired heterocyclic groups and conductive electronic groups.

[0109] Functional polyurethane Example A4.

[0110] This embodiment provides a functional polyurethane and its preparation method. This functional adhesive has extremely high electronic conductivity. The preparation method includes the following steps S1 to S7: S1. Polyol Mixing: At 85°C, PEG-2000 (8 g), PPG-1000 (7 g), and DMPA (0.6 g) were added to a container at one time and stirred at 600 rpm for 1.5 h.

[0111] S2. Prepolymer formation: HDI (5 g) was added dropwise at a constant rate for 40 min while maintaining 85℃. DBTDL (0.06 g) was then added in one go, and the mixture was stirred at 800 rpm for 2 h.

[0112] S3. Chain Extension: After cooling to 65°C, add 4-aminophenol (containing functional group material, 1.2 g, dissolved in 6 mL DMF) and 6-amino-1,3-dimethyluracil (containing heterocyclic group material, 1.2 g, dissolved in 6 mL DMF), and stir at 500 rpm for 1 h. The -N(CH3) group (amide nitrogen) in the heterocyclic group material is inactive, so -NH2 will preferentially react with -NCO, reducing the influence on the pyrimidine ring and binding the pyrimidine ring in the prepolymer.

[0113] S4. Neutralization: Maintain 60°C, add TEA (0.35 g), and stir at 400 rpm for 30 min until pH is reached.

[0114] S5. Water dispersion: At room temperature, add 50 mL of water dropwise and stir at 1000 rpm for 1 h.

[0115] S6. Secondary chain extension: At room temperature, add HDO (0.8 g) all at once and stir at 400 rpm for 40 minutes.

[0116] S7. Removal and Concentration: After dialyzing in pure water for 120 h, the solution is rotary evaporated for 1.5 h at 40 °C and a vacuum of 10 mbar to remove some of the solvent water, resulting in a functional polyurethane aqueous solution concentrated to a solid content of 40%.

[0117] Conductivity test: The functional polyurethane aqueous solution obtained in step S7 was poured into a Teflon mold, then dried under vacuum at 70°C for 10 hours, and then cured at 110°C for 3 hours to obtain functional polyurethane. After film laying, a four-probe test was performed, and the resistivity was 8.34 mΩ·cm and the conductivity was 119.9 S / cm, proving that the synthesized polyurethane has high electronic conductivity.

[0118] Example B1 (Sodium alginate-polyacrylic acid-barbituric acid-maleic acid-functional polyurethane functional binder and the battery made therefrom).

[0119] This embodiment provides a button cell battery, further comprising the functional polyurethane of embodiment A1 described above being formulated into a functional binder, and a lithium-ion battery being prepared, including the following steps G1 to G3: G1. Preparation of the functional adhesive: At 50°C, with a stirring speed of 600 rpm, 0.25 g of sodium alginate and 0.25 g of polyacrylic acid were dissolved in 9.5 g of deionized water over 4 h, and the pH was adjusted to 7.3 with 0.12 g of sodium hydroxide to obtain a polymer aqueous solution. 0.05 g of barbituric acid and 0.1 g of maleic acid were added to the polymer aqueous solution, and the pH was adjusted to 6.0. The solution was stirred at 50°C with a stirring speed of 400 rpm for 60 min until homogeneous. 1.67 g of the functional polyurethane aqueous solution prepared in step S7 of Example A1 was added, and the solution was stirred at 50°C with a stirring speed of 400 rpm for 60 min until homogeneous, obtaining an aqueous solution containing the functional adhesive.

[0120] G2. Preparation of negative electrode sheet: 30 nm silicon (120 mg), the above-mentioned aqueous solution containing functional binder (150 mg), conductive agent (300 mg, 5% concentration of multi-walled carbon nanotube aqueous solution) and 300 μL water are mixed and homogenized in a homogenizer at a speed of 400 r / min for 180 s to obtain a mixture slurry. The mixture slurry is coated on copper foil, dried at 60℃ for 60 min, and then cured at 120℃ for 12 h. The negative electrode sheet is then cut into sheets.

[0121] G3. Preparation of lithium-ion batteries: The above negative electrode sheet is transferred to a glove box, and a 2016 coin cell is assembled using a lithium sheet as the counter electrode.

[0122] Blank group A1 and button cell blank group B1.

[0123] Compared to Example A1, blank group A1 does not contain functional polyurethane. It consists only of a solution obtained by dissolving 0.25 g of sodium alginate and 0.25 g of polyacrylic acid in 9.5 g of deionized water, after undergoing the same sodium hydroxide pH adjustment step. Step S7 is replaced with drying at 120°C for 12 h, while the remaining steps remain unchanged. This solution serves as the binder. Compared to coin cell Example B1, coin cell blank group B1 uses the binder from blank group A1, while the remaining steps remain unchanged.

[0124] The performance of the above-mentioned batteries was tested, including constant current charge-discharge tests on the coin cells assembled in the third step. The current density during activation was 178.95 mA / g, and the current densities during various rate tests ranged from 357.9 mA / g to 17895 mA / g, with a voltage window of 0.01 V to 1.5 V. All current densities mentioned in this application refer to the current per unit mass of the film layer on the current collector in the electrode. The test results for Example B1 and Blank Group B1 are as follows: Figure 4 As shown, when sodium alginate-polyacrylic acid-barbituric acid-maleic acid-functionalized polyurethane is used as the functional binder and 30 nm silicon is used as the active material, the battery can be stabilized at approximately 900 mAh g at a current density of 17895 mA / g (5C). -1 The battery can cycle at its capacity. In contrast, lithium-ion batteries using sodium alginate-polyacrylic acid as a binder only achieve about 20 mAh g⁻¹ at the same rate. -1 The results are far inferior to those of Example B1, indicating that the functional polyurethane introduces more ion transport channels, and that barbituric acid and maleic acid introduce electrostatic adsorption and multiple hydrogen bonding, improving crosslinking and bonding strength. The functional binder also helps form a high-ionic-conductivity SEI film, significantly improving the cycle performance, conductivity, and rate performance of batteries made from nano-silicon-based anode materials.

[0125] Example B2 (Polyacrylic acid-guanidinium urea-sulfuric acid-functional polyurethane functional binder and the battery made therefrom).

[0126] This embodiment provides a button cell battery, further comprising the functional polyurethane of embodiment A2 described above being formulated into a functional binder, and a lithium-ion battery being prepared, including the following steps G1 to G3: G1. Preparation of the functional adhesive: At 50°C and with a stirring speed of 400 rpm, 0.5 g of polyacrylic acid was dissolved in 9.5 g of deionized water over 4 h, and the pH was adjusted to 8.0 with 0.17 g of lithium hydroxide to obtain a polymer aqueous solution. 0.03 g of guanidinium urea and 0.01 g of sulfuric acid were added to the polymer aqueous solution to adjust the pH to 6.5. The solution was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to ensure homogeneity. 1.42 g of the functional polyurethane aqueous solution prepared in step S7 of Example A2 was added, and the solution was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to ensure homogeneity, resulting in an aqueous solution containing the functional adhesive.

[0127] G2. Preparation of negative electrode sheet: BTR silicon carbon (120 mg), the above-mentioned aqueous solution containing functional binder (150 mg), conductive agent (300 mg, 5% concentration of multi-walled carbon nanotube aqueous solution) and 300 μL of water are mixed and homogenized in a homogenizer at a speed of 400 r / min for 180 s to obtain a mixture slurry. The mixture slurry is coated on copper foil, dried at 60℃ for 60 min, and then cured at 130℃ for 12 h. The negative electrode sheet is then cut into sheets.

[0128] G3. Preparation of lithium-ion batteries: The above negative electrode sheet is transferred to a glove box, and a 2016 coin cell is assembled using a lithium sheet as the counter electrode.

[0129] Blank group A2 and button cell blank group B2.

[0130] Compared to Example A2, blank group A2 does not contain functional polyurethane, but only a solution obtained by dissolving 0.5 g of polyacrylic acid in 9.5 g of deionized water after undergoing the same sodium hydroxide pH adjustment step, with step S7 changed to drying at 130°C for 12 h, while the other steps remain unchanged, serving as the binder. Compared to coin cell Example B2, coin cell blank group B2 uses the binder of blank group A2, while the other steps remain unchanged.

[0131] A constant potential electrochemical impedance spectroscopy test was performed on the negative electrode of the above battery. The frequency range was 100 MHz to 100 kHz, and the voltage perturbation was 10 mV. The test results are as follows: Figure 5As shown, the negative electrode sheet using polyacrylic acid-guanidinium urea-sulfuric acid-functional polyurethane as the functional binder exhibits significantly lower internal resistance and SEI film resistance after cycling compared to the battery using polyacrylic acid as the binder. This indicates that the functional polyurethane introduces more ion transport channels, and that guanidinium urea and sulfuric acid, as crosslinking agents and acidic raw materials, significantly enhance the reaction kinetics of BTR's silicon-carbon negative electrode during the lithium insertion / extraction stage, forming a uniform SEI film with high ionic conductivity. Macroscopically, this results in lower internal resistance and SEI film resistance under the same constant potential impedance test conditions.

[0132] Example B3 (Polyacrylic acid-guanidinoacetic acid-phytic acid-functional polyurethane functional binder and the battery made therefrom).

[0133] This embodiment provides a button cell battery, further comprising the functional polyurethane of embodiment A3 described above being formulated into a functional binder, and a lithium-ion battery being prepared, including the following steps G1 to G3: G1. Preparation of the functional adhesive: At 50°C and with a stirring speed of 400 rpm, 0.5 g of polyacrylic acid was dissolved in 9.5 g of deionized water over 4 h, and the pH was adjusted to 6.5 with 0.26 g of sodium hydroxide to obtain a polymer aqueous solution. 0.03 g of guanidinoacetic acid and 0.05 g of phytic acid were added to the polymer aqueous solution, and the pH was adjusted to 6.3. The mixture was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to ensure homogeneity. 1 g of the functional polyurethane aqueous solution prepared in step S7 of Example A3 was added, and the mixture was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to ensure homogeneity, resulting in an aqueous solution containing the functional adhesive.

[0134] G2. Preparation of negative electrode sheet: BTR silicon carbon (120 mg), the above-mentioned aqueous solution containing functional binder (150 mg), conductive agent (300 mg, 5% concentration of multi-walled carbon nanotube aqueous solution) and 300 μL of water are mixed and homogenized in a homogenizer at a speed of 400 r / min for 180 s to obtain a mixture slurry. The mixture slurry is coated on copper foil, dried at 60℃ for 60 min, and then cured at 110℃ for 16 h. The negative electrode sheet is then cut into sheets.

[0135] G3. Preparation of lithium-ion batteries: The above negative electrode sheet is transferred to a glove box, and a 2016 coin cell is assembled using a lithium sheet as the counter electrode.

[0136] Blank group A3 and button cell blank group B3.

[0137] Compared to Example A3, blank group A3 does not contain functional polyurethane, but only a solution obtained by dissolving 0.5g of polyacrylic acid in 9.5g of deionized water after undergoing the same sodium hydroxide pH adjustment step, with step S7 changed to drying at 110°C for 16h, while the other steps remain unchanged, serving as the binder. Compared to coin cell Example B3, coin cell blank group B3 uses the binder of blank group A3, while the other steps remain unchanged.

[0138] The above-mentioned batteries underwent performance testing, including constant current charge-discharge testing of the coin cells assembled in step three. The activation current density was 5000 mA / g to 1000 mA / g, activated from high to low rate. The long-cycle current density was 500 mA / g, and the voltage window was 0.01 V to 1.5 V. The test results for Example B3 and Blank Group B3 are as follows: Figure 6 As shown in the figure, it can be seen that when polyacrylic acid-guanidinoacetic acid-phytic acid-functionalized polyurethane is used as the functional binder and BTR silicon carbide is used as the active material, it can achieve 500 mA g -1 (5C) Maintains approximately 587 mAh g at a high current density. -1 The specific capacity is higher, while lithium-ion batteries using polyacrylic acid as a binder have only about 200 mAh g at the same rate. -1 The specific capacity of the sample was far lower than that of Example B3, indicating that the functional polyurethane introduced more electron transport channels, improved reaction kinetics, and reduced internal resistance. Furthermore, guanidinoacetic acid and phytic acid, as crosslinking agents and acidic raw materials, improved crosslinking properties and bonding strength. The functional binder significantly improved the cycle performance and rate performance of the battery fabricated from BTR's silicon-carbon anode.

[0139] Example B4 (Sodium carboxymethyl cellulose-polyacrylic acid-guanidinium urea-citric acid-functional polyurethane functional binder and the battery made therefrom).

[0140] This embodiment provides a button cell battery, further comprising the functional polyurethane of embodiment A4 described above being formulated into a functional binder, and a lithium-ion battery being prepared, including the following steps G1 to G3: G1. Preparation of the functional adhesive: At 50°C and with a stirring speed of 600 rpm, 0.25 g of sodium carboxymethyl cellulose and 0.25 g of polyacrylic acid were dissolved in 9.5 g of deionized water over 4 h, and the pH was adjusted to 8.0 with 0.14 g of sodium hydroxide to obtain a polymer aqueous solution. 0.05 g of guanidinium urea and 0.1 g of citric acid were added to the polymer aqueous solution, and the pH was adjusted to 6.0. The solution was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to achieve homogeneity. 1.25 g of the functional polyurethane aqueous solution prepared in step S7 of Example A4 was added, and the solution was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to achieve homogeneity, resulting in an aqueous solution containing the functional adhesive.

[0141] G2. Preparation of negative electrode sheet: G14 CVD silicon carbon (120 mg), the above-mentioned aqueous solution containing functional binder (150 mg), conductive agent (300 mg, 5% concentration of multi-walled carbon nanotube aqueous solution) and 300 μL of water are mixed and homogenized in a homogenizer at a speed of 400 r / min for 180 s to obtain a mixture slurry. The mixture slurry is coated on copper foil, dried at 60℃ for 60 min, and then cured at 150℃ for 24 h. The negative electrode sheet is then cut into sheets.

[0142] G3. Preparation of lithium-ion batteries: The above negative electrode sheet is transferred to a glove box, and a 2016 coin cell is assembled using a lithium sheet as the counter electrode.

[0143] Blank group A4 and button cell blank group B4.

[0144] Compared to Example A4, blank group A4 does not contain functional polyurethane. It consists only of a solution obtained by dissolving 0.25 g of sodium carboxymethyl cellulose and 0.25 g of polyacrylic acid in 9.5 g of deionized water, after undergoing the same sodium hydroxide pH adjustment step. Step S7 is replaced with drying at 150°C for 24 h, while the remaining steps remain unchanged. This solution serves as the binder. Compared to coin cell Example B4, coin cell blank group B4 uses the binder from blank group A4, while the remaining steps remain unchanged.

[0145] The above-mentioned batteries underwent performance testing, including constant current charge-discharge testing of the coin cells assembled in step three. The activation current density was 90 mA / g, and the current density for each rate test ranged from 180 mA / g to 9000 mA / g, with a voltage window of 0.01 V to 1.5 V. The test results for Example B4 and the blank group B4 are as follows: Figure 7 As shown in the figure. It can be seen that sodium carboxymethyl cellulose-polyacrylic acid... When guanidinyl urea-citric acid-functionalized polyurethane is used as a functional binder and G14 CVD silicon carbide is used as the active material, it can achieve a g-resin uptake of 5000 mA. 1 (5C) maintains approximately 600 mAh g at a high current density. 1 Its specific capacity far exceeds that of lithium-ion batteries using sodium carboxymethyl cellulose-polyacrylic acid as a binder, which only have about 20 mAh g⁻¹ at the same rate. 1 The specific capacity of the sample was far lower than that of Example B3, indicating that the functional polyurethane introduced more electron transport channels, improved reaction kinetics, and reduced internal resistance. Furthermore, guanidinoacetic acid and citric acid, as crosslinking agents and acidic raw materials, improved crosslinking properties and bonding strength. The functional binder significantly improved the cycle performance and rate performance of the battery fabricated from BTR's silicon-carbon anode.

[0146] Example B5 (Polyacrylic acid-tricyanate-arginine-functional polyurethane functional binder and the battery made therefrom).

[0147] This embodiment provides a button cell battery, further comprising the functional polyurethane of embodiment A4 described above being formulated into a functional binder, and a lithium-ion battery being prepared, including the following steps G1 to G3: G1. Preparation of the functional adhesive: At 50°C and with a stirring speed of 400 rpm, 0.5 g of polyacrylic acid was dissolved in 9.5 g of deionized water over 4 h, and the pH was adjusted to 8.0 with 0.38 g of potassium hydroxide to obtain a polymer aqueous solution. 0.03 g of tricyanic acid and 0.03 g of arginine were added to the polymer aqueous solution, and the pH was adjusted to 6.3. The solution was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to ensure homogeneity. 1.25 g of the resilient functional polyurethane aqueous solution prepared in step S7 of Example A4 was added, and the solution was stirred at 50°C and with a stirring speed of 400 rpm for 60 min to ensure homogeneity, resulting in an aqueous solution containing the functional adhesive.

[0148] G2. Preparation of negative electrode sheet: BTR silicon carbon (120 mg), the above-mentioned aqueous solution containing functional binder (125 mg), conductive agent (300 mg, 5% concentration of multi-walled carbon nanotube aqueous solution) and 300 μL of water are mixed and homogenized in a homogenizer at a speed of 400 r / min for 180 s to obtain a mixture slurry. The mixture slurry is coated on copper foil, dried at 60℃ for 60 min, and then cured at 150℃ for 20 h. The negative electrode sheet is then cut into sheets.

[0149] G3. Preparation of lithium-ion batteries: The above negative electrode sheet is transferred to a glove box, and a 2016 coin cell is assembled using a lithium sheet as the counter electrode.

[0150] Blank group A5 and button cell blank group B5.

[0151] Compared to Example A4, blank group A5 does not contain functional polyurethane, but only a solution obtained by dissolving 0.5 g of polyacrylic acid in 9.5 g of deionized water after undergoing the same potassium hydroxide pH adjustment step, with step S7 changed to drying at 150°C for 20 h, while the other steps remain unchanged, serving as the binder. Compared to coin cell Example B5, coin cell blank group B5 uses the binder of blank group A5, while the other steps remain unchanged.

[0152] Cyclic voltammetry tests were performed on the above-mentioned battery at a scan rate of 0.05 mV / s. -1 The voltage window is 0.01 V to 1.5 V, and the test results are as follows: Figure 8 As shown in the figure, when polyacrylic acid-tricyanate-arginine-polyurethane is used as the binder, the graphite redox peak and silicon redox peak shown in the CV curve of the battery are more obvious than the corresponding peaks of the battery using polyacrylic acid as the binder. This indicates that the introduction of tricyanate, arginine, and functional polyurethane significantly improves the reaction kinetics of BTR silicon-carbon anode in different lithium insertion / extraction stages, increases electronic conductivity, and forms a uniform SEI film with high ionic conductivity, reducing electrolyte loss. Macroscopically, this is reflected in the battery having a larger corresponding current and corresponding redox peaks at the same scan rate.

[0153] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A functional adhesive, characterized in that, The functional adhesive has a three-dimensional network structure and includes the following raw material components: a main adhesive, a functional polyurethane, and a crosslinking agent; The main adhesive contains carboxyl groups; The functional polyurethane contains heterocyclic groups and functional groups, wherein the heterocyclic groups contain hydrogen bond acceptors and hydrogen bond donors, and the functional groups include ion-conducting groups and / or electron-conducting groups. The crosslinking agent contains hydrogen bond donors, hydrogen bond acceptors, and positively charged groups.

2. The functional adhesive according to claim 1, characterized in that: The functional polyurethane satisfies at least one of the following (1) to (8): (1) The number of hydrogen bond acceptors in the heterocyclic group is equal to the number of hydrogen bond donors in the crosslinking agent, and the number of hydrogen bond donors in the heterocyclic group is equal to the number of hydrogen bond acceptors in the crosslinking agent; (2) The heterocyclic groups include at least one of pyrimidine, pyridine, and purine groups; (3) The heterocyclic group in the polyurethane has a mass percentage content of 2% to 15%; (4) The types of ion-conducting groups include at least one of fluoroaromatics, trifluoromethylaromatics, sulfonic acids, quaternary ammonium compounds, triazoles, and imidazoline compounds; (5) The types of conductive electronic groups include at least one of thiophene, phenol, aniline, pyrrole, furan, and indole; (6) The functional groups in the polyurethane have a mass percentage content of 1% to 15%; (7) The heterocyclic group and the functional group are located between the hard segment and the soft segment in the functional polyurethane; (8) The crosslinking agent includes at least one of guanidinoacetic acid, guanidinourea, serine, malondiamide, barbituric acid, and cyanuric acid.

3. The functional adhesive according to claim 1 or 2, characterized in that: The main adhesive satisfies at least one of the following (1) to (4): (1) The mass percentage of carboxyl groups in the main adhesive is 20% to 80%; (2) The main adhesive includes at least one of polyacrylic acid and its salts; (3) The weight-average molecular weight of the main adhesive is 100,000 to 3,000,000; (4) The mass ratio of the main adhesive, the functional polyurethane, and the crosslinking agent is (1-30):(1-3):

1.

4. The functional adhesive according to claim 1 or 2, characterized in that: The functional adhesive is an aqueous solution with a solid content of 5%–50% and a pH value of 5–8; and / or, The functional adhesive contains a metal salt, which includes at least one selected from lithium, sodium, potassium, magnesium, zinc, calcium, sulfate, citrate, maleate, malonate, phytate, arginine, and lysine; and / or, The primary binder includes at least one of polyacrylic acid and its salts, and at least one of carboxymethyl cellulose and its salts, alginate and its salts, polyacrylamide and its salts, polyacrylonitrile, guar gum and its salts.

5. A method for preparing a functional adhesive as described in any one of claims 1 to 4, characterized in that, Includes the following steps: The functional adhesive is obtained by mixing the components including the main adhesive, the functional polyurethane, and the crosslinking agent.

6. The preparation method according to claim 5, characterized in that, The preparation method of the functional polyurethane includes the following steps: The raw materials, including polyols and excess polyisocyanates, are subjected to prepolymerization to obtain the first prepolymer. The raw materials comprising the first prepolymer, the material containing the heterocyclic group, and the material containing the functional group are subjected to a first chain extension treatment to obtain a second prepolymer. The raw materials, including the second prepolymer and the chain transfer agent, are subjected to a second chain extension treatment to obtain the functional polyurethane.

7. The preparation method according to claim 6, characterized in that: Materials containing the aforementioned heterocyclic groups include 5-(hydroxymethyl)uracil, 6-amino-1,3-dimethyluracil, 5,6-diamino-2,4-dihydroxypyrimidine, 4,5-diamino-6-hydroxy-2-mercaptopyrimidine, 5-aminouracil, 5-hydroxyuracil, 5-(hydroxymethyl)thymine, 5-aminothymine, 5-aminocytosine, 5-(hydroxymethyl)cytosine, and 1,3,5-tris(hydroxymethyl) At least one of isocyanuric acid, 5,5-dimethylisocyanuric acid, 2-amino-4,6-dihydroxypyrimidine, 4-amino-2,6-dichloropyrimidine, 2-hydroxypyridine, 3-hydroxypyridine, 4-hydroxypyridine, 2-aminopyridine, 3-aminopyridine, 4-aminopyridine, 3,5-dichloro-2-hydroxypyridine, 5-amino-2-methylpyridine, 2,6-dihydroxypyridine, and 2,6-diaminopyridine; and / or, Materials containing the aforementioned functional groups include at least one of 3-fluoro-1,2-phenylenediamine, 5-fluoro-2,3-pyridinediamine, 3-(trifluoromethyl)-1,2-phenylenediamine, 2-amino-5-sulfonic acid phenol, N-(2-aminoethyl)-N-methylimidazolium, 4-amino-3-fluorobenzoic acid, 2,6-diaminopyridine-3-sulfonic acid, 3-amino-1-propanol sulfonic acid, N,N-dimethyl-1,3-propanediamine, 5-amino-2-fluorophenol, 3-amino-1,2,4-triazol-5-carboxylic acid, 2-aminothiophene, 3-aminothiophene, 4-aminophenol, 2,5-diaminothiophene, 4-hydroxyaniline, 3-hydroxyaniline, 3-aminopyrrole, 3-aminofuran, 3,4-diaminothiophene, N-(2-aminoethyl)pyrrole, and 5-aminoindole; and / or, The molar ratio of the polyisocyanate to the material containing the heterocyclic group is (2-10):1; and / or, The molar ratio of the polyisocyanate to the material containing the functional group is (2-15):

1.

8. The preparation method according to claim 6 or 7, characterized in that: The polyols include hydrophilic polyols and hydrophobic polyols, wherein the mass ratio of the hydrophilic polyol to the hydrophobic polyol is (1.5–4):1; and / or, The molar ratio of the polyol to the polyisocyanate is 1:(0.6–2.4); and / or, The raw materials for the prepolymer treatment include carboxyl-containing polyols and / or catalysts; and / or, The chain transfer agent comprises at least one selected from ethylenediamine, 1,4-butanediol, 1,3-propanediamine, 1,6-hexanediamine, isophorone diamine, diethylenetriamine, ethylene glycol, 1,3-propanediol, 1,5-pentanediol, diethylene glycol, trimethylolpropane, 1,4-cyclohexanediol, m-phenylenediamine, and polyetheramine; and / or, Prior to the second chain extension treatment, at least one of the following steps is included: neutralization treatment, quaternization treatment, and water dispersion treatment of the second prepolymer.

9. The preparation method according to any one of claims 5 to 7, characterized in that: The mass ratio of the main adhesive, the functional polyurethane, and the crosslinking agent is (1-30):(1-3):1; and / or, The mixing process includes the following steps: The main binder, metal hydroxide, and water are formulated into a first solution, the pH of which is 5 to 8.5; The first solution, the crosslinking agent, and the acidic raw materials are used to prepare a second solution, the pH value of which is 5 to 7.

5. The second solution is formulated with the functional polyurethane to form a solution containing the functional adhesive.

10. A lithium-ion battery, characterized in that: The raw material components of the negative electrode film of the lithium-ion battery include the functional binder as described in any one of claims 1 to 4, or the functional binder prepared by the preparation method as described in any one of claims 5 to 9.

Images