A silicon-carbon negative electrode binder and a preparation method thereof, and a silicon-carbon negative electrode

Abstract

This invention discloses a silicon-carbon anode binder and its preparation method, as well as a silicon-carbon anode, belonging to the field of lithium-ion battery technology. The silicon-carbon anode binder and its preparation method include: adding a polyarylene ether resin to a polar aprotic solvent and sulfonating it to obtain a sulfonated polymer; selecting route A or route B according to the type of thermal crosslinking modifier to obtain the binder; when the thermal crosslinking modifier is an amine compound containing benzocyclobutene or a phenolic derivative substituted with maleimide, route A is selected; when the thermal crosslinking modifier is an epoxysilane coupling agent, route B is selected. This invention abandons traditional processes and uses sulfolane as the reaction medium. This solvent has good solubility and stability, can inhibit the degradation of the polymer backbone, and makes the reaction mild and controllable; at the same time, two differentiated grafting paths are designed for different crosslinking groups to ensure the activity of functional groups. During baking, a three-dimensional network structure is formed, buffering the volume expansion of silicon-carbon particles and maintaining the integrity of the electrode structure.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion batteries, and particularly to a silicon-carbon anode binder and its preparation method, as well as a silicon-carbon anode. Background Technology

[0002] Lithium-ion batteries are widely used in portable consumer electronics products such as mobile phones, laptops, and digital cameras due to their advantages such as high energy density, environmental friendliness, and absence of memory effect. In recent years, the rapid development of thinner, lighter, smarter, and more functional consumer electronics has placed higher demands on the energy density of lithium-ion batteries. Using high-capacity active materials can significantly increase battery capacity and is one of the effective ways to improve battery energy density.

[0003] Traditional graphite anodes have low theoretical capacity, while silicon anodes have high theoretical capacity, making them highly promising anode materials for lithium-ion batteries. However, due to the significant volume effect of silicon anodes, they are prone to pulverization during charge and discharge, leading to short battery life and poor performance stability. In response, researchers have adopted silicon-carbon composite materials as anode materials, resulting in improved battery performance. In the use of silicon-carbon composite materials, binders play a crucial role in suppressing the expansion and pulverization of silicon materials and improving battery performance.

[0004] Currently, the traditional binders widely used in the industry mainly include polyvinylidene fluoride (PVDF) and polyacrylic acid (PAA). Among them, PVDF binders rely on the toxic organic solvent N-methylpyrrolidone (NMP) for dissolution, and lack ion conduction sites in the molecular chain, resulting in low ion conduction efficiency. At the same time, it is prone to swelling in the electrolyte, and its mechanical strength is insufficient, which cannot effectively buffer the volume expansion of silicon-carbon anodes, leading to poor electrode cycle performance. Although PAA binders have certain hydrogen bonding and mechanical strength, their ion conductivity is poor, and their electrolyte stability is insufficient during long-term cycling, making it difficult to meet the harsh usage requirements of silicon-carbon anodes.

[0005] To address the shortcomings of traditional adhesives, researchers have turned their attention to sulfonated polymer adhesives. The sulfonic acid groups introduced into their molecular chains provide ion conduction sites, improving the ion migration efficiency of the electrodes. Simultaneously, the sulfonic acid groups form strong interactions with hydroxyl and amino groups on the surface of the active material, enhancing adhesion and interfacial stability. However, existing sulfonated polymer adhesive preparation processes have significant drawbacks: industrial production often uses toxic polar organic solvents such as NMP and dimethylformamide (DMF) as reaction media, employing a dissolution-sulfonation-precipitation route. This not only results in highly toxic organic solvents that easily cause environmental pollution but also presents challenges such as difficult solvent recovery, cumbersome process steps, and high production costs, hindering large-scale, green production.

[0006] Furthermore, some sulfonated polymer binders lack sufficient crosslinking properties and mechanical buffering capacity, making them prone to breakage under repeated volume expansion of the silicon-carbon anode. Additionally, some crosslinking groups introduced in the preparation process exhibit poor stability in acidic sulfonation environments, leading to binder failure. Therefore, developing a silicon-carbon anode binder with a green and environmentally friendly preparation process, low cost, and excellent mechanical buffering capacity, ionic conductivity, and interfacial stability is crucial for promoting the commercial application of silicon-carbon anodes. Summary of the Invention

[0007] This invention provides a silicon-carbon anode binder and its preparation method, as well as a silicon-carbon anode, aiming to develop a silicon-carbon anode binder with a green and environmentally friendly preparation process, low cost, and excellent mechanical buffering capacity, ion conductivity, and interfacial stability.

[0008] The objective of this invention can be achieved through the following technical solutions: In a first aspect, the present invention provides a method for preparing a silicon-carbon anode binder, comprising the following steps: S1. Add polyarylene ether resin to a polar aprotic solvent, heat to dissolve and cool, then add sulfonating agent to carry out sulfonation reaction to obtain sulfonated polymer. S2. Depending on the type of thermal crosslinking modifier, select route A or route B to obtain the binder; When the thermal crosslinking modifier is an amine compound containing benzocyclobutene or a phenolic derivative substituted with maleimide, choose route A; When the thermal crosslinking modifier is an epoxy silane coupling agent, route B should be selected; The A route specifically involves: first introducing a thermal crosslinking modifier into the sulfonated polymer to obtain a functionalized sulfonated polymer, then neutralizing and purifying the precipitate with an alkaline aqueous solution to obtain a binder; The B route specifically involves: first, neutralizing, precipitating, and purifying the sulfonated polymer with an alkaline aqueous solution to obtain a solid sulfonated polymer product, and then introducing a thermal crosslinking modifier to obtain a binder.

[0009] Further, in step S1, the polyarylether resin is any one of polyether ether ketone, polyphenylene ether, and polyarylether ketone.

[0010] Further, in step S1, the mass ratio of the polyarylene ether resin, the polar aprotic solvent, and the sulfonating agent is 100:(1000-1500):(40-80).

[0011] Furthermore, in step S1, the polar aprotic solvent is sulfolane.

[0012] Further, in step S1, the sulfonating agent is any one of chlorosulfonic acid, 98% concentrated sulfuric acid, and fuming sulfuric acid, preferably chlorosulfonic acid.

[0013] Furthermore, in step S1, the heating temperature is 60–80°C.

[0014] Furthermore, in step S1, the cooling temperature is 30–50°C.

[0015] Furthermore, in step S1, the sulfonation reaction temperature is 30–50°C, and the reaction time is 3–6 hours.

[0016] Furthermore, when route A is selected and the thermal crosslinking modifier is an amine compound containing benzocyclobutene, the sulfonating agent used in step S1 is chlorosulfonic acid, and step S2 specifically involves: S21. Add an amine compound containing benzocyclobutene to the sulfonated polymer, heat to 60-70℃ and react for 3-5 hours to obtain a functionalized sulfonated polymer. The mass ratio of the sulfonated polymer to the amine compound containing benzocyclobutene is 100:(5-10); The amine compound containing benzocyclobutene is any one of 4-aminobenzocyclobutene, 3-aminobenzocyclobutene, 4-(aminomethyl)benzocyclobutene, 4-(2-aminoethyl)benzocyclobutene, and 3,4-diaminobenzocyclobutene; preferably 4-aminobenzocyclobutene.

[0017] S22. An alkaline aqueous solution is added to the functionalized sulfonated polymer for in-situ neutralization and precipitation. After purification, a silicon-carbon anode binder is obtained.

[0018] Furthermore, when route A is selected and the thermal crosslinking modifier is a maleimide-substituted phenolic derivative, the sulfonating agent used in step S1 is chlorosulfonic acid, and step S2 specifically involves: S21. Add N-(4-hydroxyphenyl)maleimide and triethylamine to the sulfonated polymer and stir at 50°C for 1-5 h to obtain the functionalized sulfonated polymer. The mass ratio of sulfonated polymer, N-(4-hydroxyphenyl)maleimide, and triethylamine is 100:(8-12):(3-5); The maleimide-substituted phenolic derivative is any one of N-(4-hydroxyphenyl)maleimide, N-(2-hydroxyphenyl)maleimide, N-(3-hydroxyphenyl)maleimide, and N-(4-hydroxy-3-methylphenyl)maleimide; preferably N-(4-hydroxyphenyl)maleimide.

[0019] S22. An alkaline aqueous solution is added to the functionalized sulfonated polymer for in-situ neutralization and precipitation. After purification, a silicon-carbon anode binder is obtained.

[0020] Furthermore, when route B is selected and the thermal crosslinking modifier is an epoxy silane coupling agent, step S2 specifically involves: S21. Add an alkaline aqueous solution to the sulfonated polymer, neutralize the precipitate in situ, and obtain the sulfonated polymer solid product after purification. S22. Disperse the sulfonated polymer solid product in an aqueous ethanol solution, add an epoxy silane coupling agent and stir until uniform, then dry to obtain a silicon-carbon anode binder. The mass ratio of the sulfonated polymer solid product, the ethanol aqueous solution, and the epoxy silane coupling agent is 100:(500-1000):(3-6); The volume ratio of anhydrous ethanol to deionized water in an aqueous ethanol solution is (7-9):(1-3); The epoxy silane coupling agent is any one of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-glycidyl etheroxypropylmethyldimethoxysilane, preferably 3-glycidyl etheroxypropyltrimethoxysilane.

[0021] Furthermore, in routes A and B, the alkaline aqueous solution is prepared from any one of alkali metal hydroxides, alkali metal carbonates, and alkali metal acetates.

[0022] Furthermore, the alkali metal hydroxide includes any one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide; the alkali metal carbonate includes any one or more of lithium carbonate, sodium carbonate, and potassium carbonate; and the alkali metal acetate includes any one or more of lithium acetate, sodium acetate, and potassium acetate.

[0023] Furthermore, the concentration of the alkaline aqueous solution is 0.5–1.5 mol / L.

[0024] Furthermore, the pH of the system after treatment with the alkaline aqueous solution is 7.0–9.0.

[0025] Furthermore, the purification process includes filtration, washing with water 3 to 5 times, and finally vacuum drying at 80 to 100°C.

[0026] Secondly, the present invention provides a silicon-carbon anode binder, which is prepared by any one of the preparation methods described above.

[0027] Thirdly, the present invention provides a silicon-carbon anode, prepared using the aforementioned silicon-carbon anode binder, the preparation method comprising the following steps: Silicon-carbon active material, conductive agent and silicon-carbon anode binder are mixed, deionized water slurry is added for 4 hours, coated on the surface of current collector, dried and then vacuum heat treated to obtain silicon-carbon anode. Furthermore, the mass ratio of the silicon-carbon active material, conductive agent, silicon-carbon negative electrode binder, and deionized water is (85-95):(2-4):(3-5):(80-120).

[0028] Furthermore, the drying temperature is 60–100°C.

[0029] Furthermore, the vacuum heat treatment is performed at a temperature of 150–300°C for a duration of 1–3 hours.

[0030] Furthermore, the conductive agent is any one of graphene, carbon nanotubes, conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, and carbon nanofiber.

[0031] Furthermore, the silicon-carbon active material is composed of 10-30 wt% nano-silicon and 70-90 wt% carbon material, and the nano-silicon has a particle size of 10-30 nm.

[0032] Furthermore, the current collector can be either copper foil or copper mesh.

[0033] The beneficial effects of this invention are: 1. In step S1 of this invention, the polyarylene ether resin is dissolved by heating in a polar aprotic solvent, which can achieve uniform dispersion of the resin to provide a stable reaction environment. After cooling, a sulfonating agent is added to carry out the sulfonation reaction, which can precisely control the degree of sulfonation and avoid over-sulfonation or resin degradation caused by high temperature. The sulfonic acid groups and sulfonyl chloride groups introduced into the molecular chain not only endow the polymer with good water solubility / dispersibility and reduce dependence on toxic organic solvents, but also provide active sites for subsequent thermal crosslinking modification. At the same time, the sulfonation modification and the aromatic ring structure of the polyarylene ether resin itself work synergistically to endow the material with excellent intrinsic flame retardant properties. Combined with the high mechanical strength and chemical stability of the polyarylene ether resin, it lays the foundation for the buffering performance, electrolyte resistance and safety performance of the binder; step S2 is based on the chemical properties of the thermal crosslinking modifier. Differentiated selection of routes A and B maximizes the function of the modifier. Route A is chosen for amine compounds containing benzocyclobutene groups and phenolic derivatives substituted with maleimide groups. This strategy of modification followed by neutralization avoids interference from the highly polar environment generated by the dissociation of sulfonic acid groups during neutralization, ensuring precise grafting of thermally crosslinked groups, significantly improving the crosslinking density and interfacial adhesion of the binder, and enhancing the bonding force between the binder and silicon-carbon anode active materials and current collectors. Route B is chosen for epoxy silane coupling agents. This strategy of neutralization followed by modification allows for the removal of residual acidic sulfonating agents in the system through neutralization, precipitation, and purification using alkaline aqueous solutions. This avoids the damage of the epoxy groups by the acidic environment and ensures the complete preservation of the functional groups of the silane coupling agent. During the baking process of battery electrode preparation, these functional groups undergo thermal cross-linking reaction to form a robust three-dimensional network structure. This cross-linking network can inhibit the melting and dripping of polymers at high temperatures and thermal decomposition, promote the formation of a dense carbon layer, and further enhance the flame retardant properties of the binder. At the same time, this structure acts like an "elastic armor" to bind silicon carbon particles, effectively buffering their huge volume expansion during charging and discharging, and maintaining the integrity of the electrode structure.

[0034] 2. This invention abandons the traditional concentrated sulfuric acid / fuming sulfuric acid-water precipitation method or NMP solvent method, and innovatively uses sulfolane as the reaction medium. Sulfolane has excellent solubility for polyarylene ether resins and is chemically stable, effectively inhibiting polymer backbone degradation during sulfonation and maintaining the high molecular weight and mechanical strength of the material. At the same time, the high boiling point and stability of sulfolane make the reaction process more mild and controllable.

[0035] 3. The binder prepared by this invention integrates the triple advantages of lithium sulfonate groups (ionic conductivity / assisted flame retardancy), rigid molecular skeleton (mechanical support / heat resistance / flame retardancy) and cross-linking network (anti-swelling / buffering / flame retardant reinforcement). The lithium sulfonate group provides a highly efficient lithium-ion transport channel, reducing the internal resistance of the electrode. The sulfonate group can further enhance the flame retardant effect through dehydration and char formation, as well as by blocking oxygen. The rigid molecular framework originates from the aromatic ring structure of the polyarylene ether resin matrix. The high bond energy of the aromatic ring endows the electrode with excellent heat resistance. Combined with the synergistic effect of sulfonation modification, a dual flame retardant guarantee is constructed. Even if the epoxy silane coupling agent introduced via route B does not contain aromatic groups, it can still maintain the rigid support effect and flame retardant performance of the framework through cross-linking with the polyarylene ether matrix. The cross-linking network is formed by the chemical bonding between the modifier and the polyarylene ether resin. On the one hand, it can effectively inhibit the swelling and deformation of the electrode during cycling, significantly improving the cycle life of the silicon-carbon anode. On the other hand, it can enhance the thermal stability of the material, inhibiting high-temperature decomposition and flame spread, forming a triple flame retardant synergistic system with the sulfonate group and the rigid framework. Experiments show that this binder exhibits excellent peel strength, electrochemical stability, and flame retardant safety performance in silicon-carbon anodes. Detailed Implementation

[0036] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0037] In a first aspect, the present invention provides a method for preparing a silicon-carbon anode binder, comprising the following steps: S1. Add polyarylene ether resin to a polar aprotic solvent, heat to dissolve and cool, then add sulfonating agent to carry out sulfonation reaction to obtain sulfonated polymer. Heating polyarylene ether resins into a polar aprotic solvent can achieve uniform resin dispersion and provide a stable reaction environment. After cooling, a sulfonating agent is added to carry out the sulfonation reaction, which can precisely control the degree of sulfonation and avoid over-sulfonation or resin degradation caused by high temperature. The sulfonic acid groups and sulfonyl chloride groups introduced into the molecular chain not only endow the polymer with good water solubility / dispersibility and reduce dependence on toxic organic solvents, but also provide active sites for subsequent thermal crosslinking modification. At the same time, the sulfonation modification and the aromatic ring structure of the polyarylene ether resin itself work synergistically to endow the material with excellent intrinsic flame retardant properties. Combined with the high mechanical strength and chemical stability of polyarylene ether resin, it lays the foundation for the buffering performance, electrolyte resistance and safety performance of the binder. S2. Depending on the type of thermal crosslinking modifier, select route A or route B to obtain the binder; When the thermal crosslinking modifier is an amine compound containing benzocyclobutene or a phenolic derivative substituted with maleimide, choose route A; When the thermal crosslinking modifier is an epoxy silane coupling agent, route B should be selected; The A route specifically involves: first introducing a thermal crosslinking modifier into the sulfonated polymer to obtain a functionalized sulfonated polymer, then neutralizing and purifying the precipitate with an alkaline aqueous solution to obtain a binder; The B route specifically involves: first, neutralizing, precipitating, and purifying the sulfonated polymer with an alkaline aqueous solution to obtain a solid sulfonated polymer product, and then introducing a thermal crosslinking modifier to obtain a binder.

[0038] Choosing routes A and B based on the differentiated chemical properties of the thermal crosslinking modifiers maximizes their functionality. Route A employs a pre-modification followed by neutralization strategy for amine compounds containing benzocyclobutene groups and phenolic derivatives substituted with maleimide groups, achieving precise grafting to enhance the crosslinking density and interfacial adhesion of the binder. Route B employs a pre-neutralization followed by modification strategy for epoxy silane coupling agents, avoiding the damage of the epoxy groups by the acidic environment and ensuring the retention of functional groups. During the baking process of battery electrode preparation, these functional groups undergo thermal crosslinking reactions, forming a robust three-dimensional network structure. This crosslinking network can inhibit the melting and dripping of polymers at high temperatures and thermal decomposition, promote the formation of a dense carbon layer, and further enhance the flame retardant properties of the binder. At the same time, this structure acts like an "elastic armor" to bind silicon carbon particles, effectively buffering their huge volume expansion during charging and discharging, and maintaining the integrity of the electrode structure. The two differentiated processes, A and B, can be flexibly selected according to the chemical properties of the thermal crosslinking modifier, maximizing the preservation of the activity of crosslinking groups, avoiding group deactivation or impurity interference, and ensuring that the subsequent thermal crosslinking reaction proceeds fully to form a stable and dense three-dimensional crosslinking network.

[0039] In some embodiments, in step S1, the polyarylether resin is any one of polyetheretherketone, polyphenylene ether, and polyaryletherketone. These resins all possess a rigid aromatic skeleton, which not only imparts excellent mechanical strength and electrolyte stability to the binder but also achieves intrinsic flame retardancy through the aromatic ring structure, thereby improving the overall performance of the binder at the matrix level and meeting the application requirements of silicon-carbon anodes.

[0040] In some embodiments, in step S1, the mass ratio of the polyarylene ether resin, the polar aprotic solvent, and the sulfonating agent is 100:(1000-1500):(40-80). This ratio range ensures that the polyarylene ether resin is fully dissolved while allowing the sulfonating agent to be uniformly dispersed in the reaction system. This avoids insufficient resin dissolution due to insufficient solvent and prevents polymer backbone degradation caused by excessive sulfonating agent, thus achieving precise control over the degree of sulfonation.

[0041] In some embodiments, in step S1, the polar aprotic solvent is sulfolane. Sulfolane is chemically stable and will not undergo side reactions with the sulfonating reagent during the sulfonation process. It can effectively inhibit the degradation of the polymer backbone and maintain the high molecular weight and mechanical strength of the material. At the same time, sulfolane has no obvious toxicity and is easy to recycle, which is more in line with the green and environmentally friendly production trend compared with traditional NMP solvents.

[0042] In some embodiments, in step S1, the sulfonating agent is any one of chlorosulfonic acid, 98% concentrated sulfuric acid, and fuming sulfuric acid, preferably chlorosulfonic acid. These agents can all efficiently achieve sulfonation modification of polyarylene ether resins, introducing sulfonic acid groups to improve the ionic conductivity and water solubility of the binder. Chlorosulfonic acid is preferred because it has higher selectivity in the sulfonation reaction, fewer side reactions, and can introduce a controllable number of sulfonic acid groups and sulfonyl chloride groups onto the polymer molecular chain, which is more conducive to subsequent crosslinking modification.

[0043] In some embodiments, the heating temperature in step S1 is 60–80°C. This temperature range matches the solubility characteristics of polyarylether resins in sulfolane, enabling rapid dissolution of the resin to form a homogeneous solution system, laying the foundation for the uniformity of the subsequent sulfonation reaction, while avoiding solvent evaporation or thermal degradation of the resin due to high-temperature heating.

[0044] In some embodiments, in step S1, the cooling temperature is 30–50°C. Cooling the reaction system to this range can adjust the system to the suitable temperature range for the sulfonation reaction, avoiding excessive sulfonation or side reactions caused by high temperatures, while providing stable initial conditions for the addition of the sulfonating agent and the reaction, ensuring the controllability of the sulfonation reaction.

[0045] In some embodiments, in step S1, the sulfonation reaction temperature is 30–50°C, and the reaction time is 3–6 hours. This combination of temperature and time can precisely control the rate and progress of the sulfonation reaction, ensuring that an appropriate amount of sulfonic acid groups are introduced into the polymer molecular chain. This satisfies the requirements of subsequent crosslinking modification for active sites, while preventing excessive sulfonic acid groups from causing excessive water solubility and decreased mechanical strength of the polymer, thus ensuring a balance in the overall performance of the binder.

[0046] In some embodiments, when route A is selected and the thermal crosslinking modifier is an amine compound containing benzocyclobutene, the sulfonating agent used in step S1 is chlorosulfonic acid, and step S2 specifically involves: S21. Add an amine compound containing benzocyclobutene to the sulfonated polymer, heat to 60-70℃ and react for 3-5 hours to obtain a functionalized sulfonated polymer. To achieve efficient grafting with crosslinking agents containing amine or phenolic hydroxyl groups, chlorosulfonic acid must be selected as the sulfonating agent to introduce highly reactive sulfonyl chloride groups onto the polymer chain. Using concentrated sulfuric acid or fuming sulfuric acid would prevent effective grafting under subsequent mild conditions. This temperature and time range matches the reactivity of benzocyclobutenylamine compounds with sulfonated polymers, promoting efficient covalent bonding between amine and sulfonyl chloride groups for functionalization modification; simultaneously, it avoids excessively high temperatures leading to self-polymerization or excessively low temperatures causing incomplete reactions, ensuring the structural uniformity of the functionalized sulfonated polymer.

[0047] The mass ratio of sulfonated polymer to amine compound containing benzocyclobutene group is 100:(5-10). This ratio range can ensure that a sufficient amount of crosslinking groups are grafted onto the polymer molecular chain, providing sufficient active sites for the subsequent formation of a dense three-dimensional crosslinking network, while avoiding group aggregation caused by excessive modifier, preventing fluctuations in binder performance, and achieving precise control of crosslinking density.

[0048] The amine compounds containing benzocyclobutene groups are any one of 4-aminobenzocyclobutene, 3-aminobenzocyclobutene, 4-(aminomethyl)benzocyclobutene, 4-(2-aminoethyl)benzocyclobutene, and 3,4-diaminobenzocyclobutene; preferably 4-aminobenzocyclobutene. These compounds contain both reactive amine groups and rigid benzocyclobutene groups in their molecular structure. The amine groups enable efficient grafting, while the benzocyclobutene groups enhance the rigidity and thermal stability of the adhesive. 4-aminobenzocyclobutene is preferred because it has moderate reactivity, is widely available, and, after grafting, maximizes the interfacial adhesion and flame retardant properties of the adhesive.

[0049] S22. An alkaline aqueous solution is added to the functionalized sulfonated polymer for in-situ neutralization and precipitation. After purification, a silicon-carbon anode binder is obtained. In-situ neutralization allows the functionalized sulfonated polymer to precipitate rapidly, reducing product loss and simplifying the separation process. Subsequent purification effectively removes residual salts and unreacted monomers from the reaction system, improving the purity of the binder and ensuring the interfacial compatibility between the binder and the silicon-carbon active material, thus optimizing the electrochemical performance of the electrode.

[0050] In some embodiments, when route A is selected and the thermal crosslinking modifier is a maleimide-substituted phenolic derivative, the sulfonating agent used in step S1 is chlorosulfonic acid, and step S2 specifically involves: S21. Add N-(4-hydroxyphenyl)maleimide and triethylamine to the sulfonated polymer and stir at 50°C for 1-5 h to obtain the functionalized sulfonated polymer. Triethylamine can act as a reaction catalyst to promote the efficient binding of the phenolic hydroxyl groups of maleimide-substituted phenolic derivatives with the sulfonyl chloride groups of sulfonated polymers. The mild reaction temperature of 50°C and the time range of 1 to 5 hours can ensure that the grafting reaction proceeds fully and avoid the self-polymerization side reaction of maleimide groups caused by high temperature, thus ensuring the structural stability of the functionalized sulfonated polymer.

[0051] The mass ratio of sulfonated polymer, N-(4-hydroxyphenyl)maleimide, and triethylamine is 100:(8-12):(3-5). This ratio range allows for precise grafting of maleimide-substituted phenolic derivatives, ensuring sufficient crosslinking active sites while avoiding group aggregation caused by excessive modifier. At the same time, the amount of triethylamine used can precisely catalyze the reaction to be complete, reducing the negative impact of catalyst residue on the binder performance.

[0052] The maleimide-substituted phenolic derivatives are any one of N-(4-hydroxyphenyl)maleimide, N-(2-hydroxyphenyl)maleimide, N-(3-hydroxyphenyl)maleimide, and N-(4-hydroxy-3-methylphenyl)maleimide; preferably N-(4-hydroxyphenyl)maleimide. These derivatives contain both a reactive phenolic hydroxyl group and a rigid maleimide ring in their molecular structure. The phenolic hydroxyl group enables efficient grafting with sulfonated polymers, while the maleimide ring enhances the thermal stability and mechanical strength of the adhesive. N-(4-hydroxyphenyl)maleimide is preferred because its phenolic hydroxyl group is in the para position, resulting in less steric hindrance, higher grafting efficiency, and maximizing the crosslinking density and interfacial adhesion of the adhesive.

[0053] S22. An alkaline aqueous solution is added to the functionalized sulfonated polymer for in-situ neutralization and precipitation. After purification, a silicon-carbon anode binder is obtained. In-situ neutralization promotes the rapid precipitation of the functionalized sulfonated polymer, simplifies the separation process, and reduces product loss. Subsequent purification effectively removes residual salts, unreacted monomers, and catalysts from the system, improving the purity of the binder. This optimizes the interfacial compatibility between the binder and the silicon-carbon active material and current collector, ensuring the stability of the electrode's electrochemical performance.

[0054] In some embodiments, when route B is selected and the thermal crosslinking modifier is an epoxy silane coupling agent, step S2 specifically involves: S21. Add an alkaline aqueous solution to the sulfonated polymer, neutralize the precipitate in situ, and obtain the sulfonated polymer solid product after purification. The sulfonated polymer molecular chain contains acidic sulfonic acid groups. When an alkaline aqueous solution is added, the alkali metal cations dissociated from the alkaline substance undergo a neutralization reaction with the sulfonic acid groups to generate sulfonate groups with weaker water solubility. This causes the water solubility of the sulfonated polymer to drop sharply and precipitate in situ. Subsequent purification operations can remove residual salts, alkaline substances, and solvent impurities to obtain a high-purity sulfonated polymer solid product, laying the foundation for subsequent crosslinking reactions.

[0055] S22. Disperse the sulfonated polymer solid product in an aqueous ethanol solution, add an epoxy silane coupling agent and stir until uniform, then dry to obtain a silicon-carbon anode binder. After the sulfonated polymer solid product is dispersed in an ethanol aqueous solution, the residual active groups such as hydroxyl groups on the molecular chain are exposed. The epoxy groups of the epoxy silane coupling agent undergo ring-opening addition reactions with these active groups to achieve covalent grafting between the coupling agent and the polymer. At the same time, the siloxane groups of the coupling agent are slightly hydrolyzed in the mixed solvent to generate silanol groups. The silanol groups further undergo dehydration condensation to form -Si-O-Si- bonds, and finally a three-dimensional cross-linked network is constructed. After drying to remove the solvent, a stable silicon-carbon anode binder is obtained.

[0056] The mass ratio of the sulfonated polymer solid product, the ethanol aqueous solution, and the epoxy silane coupling agent is 100:(500-1000):(3-6). This ratio range can ensure that the sulfonated polymer is fully dispersed in the ethanol aqueous solution, and can provide sufficient but not excessive coupling agent for the crosslinking reaction. This avoids group aggregation caused by excessive coupling agent or insufficient crosslinking caused by insufficient amount, thus achieving precise control of the adhesive performance.

[0057] The volume ratio of anhydrous ethanol to deionized water in the ethanol-water solution is (7-9):(1-3). This mixed solvent has both lipophilic and hydrophilic properties, which can not only effectively disperse the sulfonated polymer solid product, but also promote the dissolution and reaction of the epoxy silane coupling agent, while avoiding the problems of poor dispersibility and low reaction efficiency caused by a single solvent.

[0058] The epoxy silane coupling agent is any one of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-glycidyl etheroxypropylmethyldimethoxysilane, preferably 3-glycidyl etheroxypropyltrimethoxysilane. This type of coupling agent molecule contains both epoxy groups and siloxane groups. The epoxy groups can react with the active groups of the sulfonated polymer to achieve grafting, while the siloxane groups can enhance the interfacial interaction between the binder and the silicon-carbon active material and current collector. 3-glycidyl etheroxypropyltrimethoxysilane is preferred because of its high reactivity and wide availability, and grafting can maximize the overall performance of the binder.

[0059] In some embodiments, in routes A and B, the alkaline aqueous solution is prepared from any one of alkali metal hydroxides, alkali metal carbonates, and alkali metal acetates. These alkaline substances can all achieve the neutralization and precipitation of sulfonated polymers without introducing harmful impurities, and can be flexibly selected according to actual process requirements to adapt to different reaction systems.

[0060] In some embodiments, the alkali metal hydroxide includes any one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide; the alkali metal carbonate includes any one or more of lithium carbonate, sodium carbonate, and potassium carbonate; and the alkali metal acetate includes any one or more of lithium acetate, sodium acetate, and potassium acetate. A clearly defined range of substances improves the repeatability of the process, facilitates direct implementation by those skilled in the art, and these substances all possess advantages such as high neutralization efficiency, easy removal, and environmental friendliness, meeting the requirements of green production.

[0061] In some embodiments, the concentration of the alkaline aqueous solution is 0.5–1.5 mol / L. This concentration range ensures both rapid and complete neutralization reaction, achieving efficient precipitation of the sulfonated polymer, while avoiding problems such as excessive alkalinity and polymer chain degradation due to excessively high concentrations, or incomplete neutralization and low precipitation efficiency due to excessively low concentrations.

[0062] In some embodiments, the pH of the system after alkaline aqueous solution treatment is 7.0–9.0. This pH range is neutral to weakly alkaline, which ensures complete precipitation of the sulfonated polymer while avoiding damage to the polymer structure from a strongly alkaline environment, ensuring the smooth progress of subsequent crosslinking reactions, and maintaining the mechanical strength and electrochemical properties of the binder.

[0063] In some embodiments, the purification process includes filtration, washing with water 3 to 5 times, and finally vacuum drying at 80 to 100°C. Filtration and multiple water washing can effectively remove salts produced by the neutralization reaction and residual alkaline substances, while vacuum drying can quickly remove moisture from the product and avoid polymer structure damage caused by high-temperature drying, ultimately obtaining a high-purity, stable binder product.

[0064] Secondly, the present invention provides a silicon-carbon anode binder, which is prepared by any one of the preparation methods described above.

[0065] Thirdly, the present invention provides a silicon-carbon anode, prepared using the aforementioned silicon-carbon anode binder, the preparation method comprising the following steps: The silicon-carbon active material, conductive agent, and silicon-carbon anode binder are mixed, and a deionized hydrate slurry is added for 4 hours. The mixture is then coated onto the surface of the current collector, dried, and subjected to vacuum heat treatment to obtain the silicon-carbon anode. The process of using deionized hydrate slurry, segmented drying, and vacuum heat treatment can ensure uniform dispersion of the electrode slurry, remove residual moisture and air bubbles from the slurry, improve the density and structural stability of the electrode sheet, and enhance the interfacial bonding force between the active material, conductive agent, and current collector.

[0066] In some embodiments, the mass ratio of the silicon-carbon active material, conductive agent, silicon-carbon anode binder, and deionized water is (85-95):(2-4):(3-5):(80-120); this balances the energy density and conductivity of the electrode, avoids excessive binder reducing capacity or insufficient binder causing electrode collapse, and ensures that the slurry has suitable viscosity and coating performance.

[0067] In some embodiments, the drying temperature is 60–100°C. This temperature range allows for rapid evaporation of deionized water in the electrode slurry while preventing premature cross-linking of the binder or damage to the active material structure caused by high temperatures, ensuring a smooth and crack-free electrode surface.

[0068] In some embodiments, the vacuum heat treatment is performed at a temperature of 150–300°C for 1–3 hours. These process conditions effectively remove residual trace amounts of moisture and air bubbles from the electrode sheet, promoting the formation of a dense cross-linked network between the binder, active material, conductive agent, and current collector, significantly improving the structural stability and interfacial bonding of the electrode.

[0069] In some embodiments, the conductive agent is any one of graphene, carbon nanotubes, conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, and carbon nanofibers. It can be flexibly selected according to actual production needs and electrode performance targets. Different conductive agents can construct complementary conductive networks, improving the electronic conduction efficiency of the electrode.

[0070] In some embodiments, the silicon-carbon active material is composed of 10-30 wt% nano-silicon and 70-90 wt% carbon material, with the nano-silicon having a particle size of 10-30 nm. This not only leverages the high capacity advantage of nano-silicon but also allows the carbon material to buffer the volume expansion of silicon. The small particle size of silicon can also shorten the lithium-ion diffusion path and improve the rate performance of the electrode.

[0071] In some embodiments, the current collector is either copper foil or copper mesh. Both possess excellent conductivity and mechanical strength, and copper mesh can further increase the contact area between the electrode and the current collector, enhancing the cycling stability of the electrode.

[0072] The specific embodiments of the present invention will be described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments.

[0073] Example 1

[0074] A method for preparing a silicon-carbon anode binder includes the following steps: S1. Add 100g of polyether ether ketone to 1200g of sulfolane, heat to 80℃ to dissolve, cool to 40℃, add 50g of chlorosulfonic acid, and react at 40℃ for 4h to obtain sulfonated polymer. S2. Add 6g of 4-aminobenzocyclobutene to 100g of sulfonated polymer, heat to 65℃ and react for 4h to obtain functionalized sulfonated polymer; slowly add 1.0mol / L lithium hydroxide aqueous solution to functionalized sulfonated polymer, adjust pH to 8.0, polymer precipitates in situ, filter, wash with water 4 times, and finally vacuum dry at 90℃ to obtain binder.

[0075] The preparation method of silicon-carbon anode includes the following steps: 90g of silicon-carbon active material (composed of 20wt% nano-silicon and 80wt% carbon material, with a nano-silicon particle size of 20nm), 3g of conductive graphite, and 4g of silicon-carbon anode binder were mixed, and 100g of deionized water slurry was added for 4 hours. The mixture was then coated onto the surface of copper foil, dried at 80℃, and vacuum heat-treated at 200℃ for 2 hours to obtain the silicon-carbon anode.

[0076] Example 2

[0077] A method for preparing a silicon-carbon anode binder includes the following steps: S1. Add 100g of polyphenylene ether to 1000g of sulfolane, heat to 60℃ to dissolve, cool to 30℃, add 45g of chlorosulfonic acid, and react at 30℃ for 5h to obtain sulfonated polymer. S2. Add 10g of N-(4-hydroxyphenyl)maleimide and 4g of triethylamine to 100g of sulfonated polymer and react at 50℃ for 3h to obtain functionalized sulfonated polymer; slowly add 1.0mol / L lithium hydroxide aqueous solution to functionalized sulfonated polymer to adjust pH to 7.5, polymer precipitates in situ, filters, washes with water 4 times, and finally dries under vacuum at 90℃ to obtain binder.

[0078] The preparation method of silicon-carbon anode includes the following steps: 90g of silicon-carbon active material (composed of 20wt% nano-silicon and 80wt% carbon material, with a nano-silicon particle size of 20nm), 3g of conductive graphite, and 4g of silicon-carbon anode binder were mixed, and 100g of deionized water slurry was added for 4 hours. The mixture was then coated onto the surface of copper foil, dried at 80℃, and vacuum heat-treated at 180℃ for 2 hours to obtain the silicon-carbon anode.

[0079] Example 3

[0080] A method for preparing a silicon-carbon anode binder includes the following steps: S1. Add 100g of polyaryletherketone to 1500g of sulfolane, heat to 60℃ to dissolve, cool to 30℃, add 70g of 98% concentrated sulfuric acid, and react at 50℃ for 6h to obtain sulfonated polymer. S2. Add 1.5 mol / L potassium hydroxide aqueous solution to the sulfonated polymer, adjust the pH to 8.5, precipitate, filter, wash with water 4 times, and finally dry under vacuum at 90℃ to obtain the sulfonated polymer solid product; disperse 100g of the sulfonated polymer solid product in 800g of ethanol aqueous solution, the volume ratio of anhydrous ethanol to deionized water in the ethanol aqueous solution is 8:2, add 5g of 3-glycidyl etheroxypropyltrimethoxysilane, stir evenly, and dry to obtain silicon-carbon anode binder; The preparation method of silicon-carbon anode includes the following steps: 90g of silicon-carbon active material (composed of 20wt% nano-silicon and 80wt% carbon material, with a particle size of 20nm for nano-silicon), 3g of conductive graphite, and 4g of silicon-carbon anode binder were mixed, and 100g of deionized water slurry was added for 4 hours. The mixture was then coated onto the surface of copper foil, dried at 80℃, and vacuum heat-treated at 160℃ for 2 hours to obtain the silicon-carbon anode.

[0081] Example 4

[0082] The only difference between this embodiment and Example 1 is that "50g chlorosulfonic acid" in S1 is changed to "75g chlorosulfonic acid"; "react at 40°C for 4h" in S1 is changed to "react at 40°C for 6h"; and "6g 4-aminobenzocyclobutene" in S2 is changed to "8g 4-aminobenzocyclobutene".

[0083] Example 5

[0084] The only difference between this embodiment and Example 2 is that "10g N-(4-hydroxyphenyl)maleimide" is changed to "12g N-(4-hydroxyphenyl)maleimide".

[0085] Example 6

[0086] The only difference between this embodiment and Example 1 is that "1.0 mol / L lithium hydroxide aqueous solution" is changed to "a mixed solution of 0.5 mol / L lithium hydroxide and 0.5 mol / L sodium hydroxide".

[0087] Comparative Example 1

[0088] The only difference between this comparative example and Example 1 is that 4-aminobenzocyclobutene is omitted. The specific steps are as follows: S1. Add 100g of polyether ether ketone to 1200g of sulfolane, heat to 80℃ to dissolve, cool to 40℃, add 50g of chlorosulfonic acid, react at 40℃ for 4h to obtain sulfonated polymer, dry to obtain adhesive.

[0089] The preparation method of silicon-carbon anode includes the following steps: 90g of silicon-carbon active material (composed of 20wt% nano-silicon and 80wt% carbon material, with a nano-silicon particle size of 20nm), 3g of conductive graphite, and 4g of silicon-carbon anode binder were mixed, and 100g of deionized water slurry was added for 4 hours. The mixture was then coated onto the surface of copper foil, dried at 80℃, and vacuum heat-treated at 250℃ for 2 hours to obtain the silicon-carbon anode.

[0090] Comparative Example 2

[0091] The only difference between this comparative example and Example 1 is that the binder was modified to commercially available SBR (styrene-butadiene rubber) and CMC (sodium carboxymethyl cellulose) with a mass ratio of SBR:CMC = 1.5:1.5.

[0092] Comparative Example 3

[0093] The only difference between this comparative example and Example 1 is that "sulfolane" is replaced with "NMP".

[0094] Test case

[0095] The binders and silicon-carbon anodes prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were subjected to performance tests, and the test items are as follows: (1) The flame retardant properties of the adhesives prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were tested according to the UL 94 vertical burning test method; (2) The silicon-carbon anodes prepared in Examples 1 to 6 and Comparative Examples 1 to 3 were cut into strips of 20cm × 2.5cm. A steel plate with a thickness of 1mm was glued to the current collector side with double-sided adhesive tape, and transparent tape was pasted on the coating side. The strips were peeled in the 180° direction at a speed of 100mm / min using a tensile testing machine, and the peel strength was measured. (3) The silicon-carbon negative electrodes obtained in Examples 1 to 6 and Comparative Examples 1 to 3 were cut into 12mm electrode sheets. The electrode sheets were transferred to a glove box filled with argon gas and assembled into 2032 coin cells. Pure lithium sheets were used as counter electrodes and Celgard 2325 polypropylene-polyethylene-polypropylene (PP-PE-PP) membranes were used as separators. The electrolyte was a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) containing 1M lithium hexafluorophosphate (LiPF6) (volume ratio 1:1). The obtained coin cells were left to stand at 25±2℃ for 12h, and then charge and discharge tests were performed on a charge and discharge tester (NEWAREBTS-5V / 10mA type manufactured by Shenzhen Newwell Electronics Co., Ltd.). The charge and discharge voltage range was 0.005-2.0V, and the current density was 0.1C. The coulombic efficiency of the first cycle and the capacity retention rate after 500 cycles were tested respectively. The test results are shown in Table 1.

[0096] Table 1

[0097] As shown in Table 1, the overall performance of the binders and silicon-carbon anodes prepared in Examples 1 to 6 is superior to that in Comparative Examples 1 to 3. Compared with Example 1, Comparative Example 1, by omitting the crosslinking agent and lacking a dense three-dimensional crosslinking network support, not only fails to effectively promote high-temperature char formation, resulting in a decrease in the flame retardant rating from V-0 to V-1, but also weakens the interfacial adhesion between the binder and the active material and current collector. Furthermore, it is difficult to restrain the volume expansion of silicon-carbon particles, leading to a significant decrease in peel strength, first-cycle coulombic efficiency, and 500-cycle capacity retention. Compared with Example 1, Comparative Example 2 uses a traditional SBR / CMC binder instead of the crosslinking binder of this invention. This type of binder lacks a rigid aromatic skeleton and flame-retardant groups, and does not possess an anti-swelling crosslinking structure; therefore, all performance aspects are comprehensively degraded. The flame retardant rating was only HB, and the peel strength and electrochemical performance were the lowest among all tested samples. Compared with Example 1, Comparative Example 3 only changed the solvent to NMP. Since NMP is less chemically stable than sulfolane, it is prone to slight side reactions with chlorosulfonic acid during the sulfonation process, which interferes with the sulfonation uniformity of the polyether ether ketone molecular chain. At the same time, NMP residue is difficult to completely remove, which will damage the interfacial compatibility between the binder and silicon carbon particles and copper foil. This not only weakens the char-forming flame retardant effect of the binder, reducing the flame retardant rating from V-0 to V-1, but also reduces the stability of the electrode interface, resulting in a significantly lower first-cycle coulombic efficiency and 500-cycle capacity retention rate than Example 1.

[0098] The above-disclosed embodiments are merely a few specific examples of the present invention. However, the embodiments of the present invention are not limited thereto, and any variations that can be conceived by those skilled in the art should fall within the protection scope of the present invention.

Claims

1. A method for preparing a silicon-carbon anode binder, characterized in that, Includes the following steps: S1. Add polyarylene ether resin to a polar aprotic solvent, heat to dissolve and cool, then add sulfonating agent to carry out sulfonation reaction to obtain sulfonated polymer. S2. Depending on the type of thermal crosslinking modifier, select route A or route B to obtain the binder; When the thermal crosslinking modifier is an amine compound containing benzocyclobutene or a phenolic derivative substituted with maleimide, choose route A; When the thermal crosslinking modifier is an epoxy silane coupling agent, route B should be selected; The A route specifically involves: first introducing a thermal crosslinking modifier into the sulfonated polymer to obtain a functionalized sulfonated polymer, then neutralizing and purifying the precipitate with an alkaline aqueous solution to obtain a binder; The B route specifically involves: first, neutralizing, precipitating, and purifying the sulfonated polymer with an alkaline aqueous solution to obtain a solid sulfonated polymer product, and then introducing a thermal crosslinking modifier to obtain a binder.

2. The method for preparing the silicon-carbon anode binder according to claim 1, characterized in that, In step S1, the polyarylether resin is any one of polyetheretherketone, polyphenylene ether, and polyaryletherketone; The mass ratio of the polyarylene ether resin, the polar aprotic solvent, and the sulfonating agent is 100:(1000-1500):(40-80); The polar aprotic solvent is sulfolane.

3. The method for preparing the silicon-carbon anode binder according to claim 1, characterized in that, In step S1, the sulfonating agent is any one of chlorosulfonic acid, 98% concentrated sulfuric acid, and fuming sulfuric acid; The heating temperature is 60–80℃; The temperature for cooling is 30–50°C; The sulfonation reaction temperature is 30–50℃, and the reaction time is 3–6 hours.

4. The method for preparing the silicon-carbon anode binder according to claim 1, characterized in that, When route A is selected and the thermal crosslinking modifier is an amine compound containing benzocyclobutene, the sulfonating agent used in step S1 is chlorosulfonic acid, and step S2 specifically involves: S21. Add an amine compound containing benzocyclobutene to the sulfonated polymer, heat to 60-70℃ and react for 3-5 hours to obtain a functionalized sulfonated polymer. The mass ratio of the sulfonated polymer to the amine compound containing benzocyclobutene is 100:(5-10); The amine compound containing benzocyclobutene is any one of 4-aminobenzocyclobutene, 3-aminobenzocyclobutene, 4-(aminomethyl)benzocyclobutene, 4-(2-aminoethyl)benzocyclobutene, and 3,4-diaminobenzocyclobutene; S22. An alkaline aqueous solution is added to the functionalized sulfonated polymer for in-situ neutralization and precipitation. After purification, a silicon-carbon anode binder is obtained.

5. The method for preparing the silicon-carbon anode binder according to claim 1, characterized in that, When route A is selected and the thermal crosslinking modifier is a maleimide-substituted phenolic derivative, the sulfonating agent used in step S1 is chlorosulfonic acid, and step S2 specifically involves: S21. Add N-(4-hydroxyphenyl)maleimide and triethylamine to the sulfonated polymer and stir at 50°C for 1-5 h to obtain the functionalized sulfonated polymer. The mass ratio of the sulfonated polymer, N-(4-hydroxyphenyl)maleimide, and triethylamine is 100:(8-12):(3-5); The maleimide-substituted phenolic derivative is any one of N-(4-hydroxyphenyl)maleimide, N-(2-hydroxyphenyl)maleimide, N-(3-hydroxyphenyl)maleimide, and N-(4-hydroxy-3-methylphenyl)maleimide; S22. An alkaline aqueous solution is added to the functionalized sulfonated polymer for in-situ neutralization and precipitation. After purification, a silicon-carbon anode binder is obtained.

6. The method for preparing the silicon-carbon anode binder according to claim 1, characterized in that, When route B is selected and the thermal crosslinking modifier is an epoxy silane coupling agent, step S2 specifically involves: S21. Add an alkaline aqueous solution to the sulfonated polymer, neutralize the precipitate in situ, and obtain the sulfonated polymer solid product after purification. S22. Disperse the sulfonated polymer solid product in an aqueous ethanol solution, add an epoxy silane coupling agent and stir until uniform, then dry to obtain a silicon-carbon anode binder. The mass ratio of the sulfonated polymer solid product, the ethanol aqueous solution, and the epoxy silane coupling agent is 100:(500-1000):(3-6); The volume ratio of anhydrous ethanol to deionized water in the ethanol-water solution is (7-9):(1-3); The epoxy silane coupling agent is any one of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, 2-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and 3-glycidyl etheroxypropylmethyldimethoxysilane.

7. The method for preparing the silicon-carbon anode binder according to claim 1, characterized in that, In routes A and B, the alkaline aqueous solution is prepared from any one of alkali metal hydroxide, alkali metal carbonate, and alkali metal acetate. The alkali metal hydroxides include any one or more of lithium hydroxide, sodium hydroxide, and potassium hydroxide; the alkali metal carbonates include any one or more of lithium carbonate, sodium carbonate, and potassium carbonate; and the alkali metal acetates include any one or more of lithium acetate, sodium acetate, and potassium acetate. The concentration of the alkaline aqueous solution is 0.5–1.5 mol / L; The pH of the system after treatment with the alkaline aqueous solution is 7.0–9.0; The purification process includes filtration, washing with water 3 to 5 times, and finally vacuum drying at 80 to 100°C.

8. A silicon-carbon anode binder, characterized in that, It is prepared by the method described in any one of claims 1-7.

9. A silicon-carbon anode, characterized in that, The anode material is prepared using the silicon-carbon anode binder as described in claim 8, and the preparation method includes the following steps: Silicon-carbon active material, conductive agent and silicon-carbon anode binder are mixed, deionized water slurry is added for 4 hours, coated on the surface of current collector, dried and then vacuum heat treated to obtain silicon-carbon anode.

10. The silicon-carbon anode according to claim 9, characterized in that, The mass ratio of the silicon-carbon active material, conductive agent, silicon-carbon negative electrode binder, and deionized water is (85-95):(2-4):(3-5):(80-120); The drying temperature is 60–100°C; The vacuum heat treatment is performed at a temperature of 150–300°C for 1–3 hours. The conductive agent is any one of graphene, carbon nanotubes, conductive carbon black, conductive graphite, Ketjen black, acetylene black, carbon fiber, and carbon nanofiber. The silicon-carbon active material is composed of 10-30 wt% nano-silicon and 70-90 wt% carbon material, and the particle size of the nano-silicon is 10-30 nm. The current collector can be either copper foil or copper mesh.

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