Modified polyacrylic acid silicon negative electrode binder, preparation method thereof and silicon negative electrode plate
By modifying polyacrylic silicon negative electrode adhesive to form a three-dimensional network structure during heating treatment, the problems of silicon negative electrode expansion and SEI film peeling are solved, and the battery cycle performance is improved.
Patent Information
- Application Number
- CN202411967054.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-30
- Publication Date
- 2025-04-04
AI Technical Summary
In the prior art, when preparing silicon negative electrodes, there are problems such as silicon negative electrode expansion, negative electrode active substances and SEI film falling off, which affects the battery circulation performance.
A modified polyacrylic silicon negative electrode adhesive is used, which is liquid at room temperature. During the heating treatment, a three-dimensional network structure is formed through an amidation reaction to inhibit the expansion of the silicon negative electrode and the detachment of the SEI film.
Effectively inhibit the expansion of silicon negative electrode, reduce the fall of negative electrode active substances and SEI film, and improve the battery circulation capacity retention rate.
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Figure CN119752361A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of lithium ion batteries, and in particular relates to a modified polyacrylic acid silicon negative electrode binder and a preparation method thereof, and a silicon negative electrode pole piece. Background Art
[0002] In order to meet the growing energy density requirements of future electrical energy storage and all-electric vehicles, various high-capacity electrode materials are being widely developed. Among them, silicon is considered to be the most promising candidate material for the next generation of lithium-ion batteries (LIBs) due to its high theoretical capacity (4200mAh / g), abundant natural resources and low working potential. However, some technical challenges still limit its commercialization. The silicon anode undergoes a large volume change during the process of lithium insertion and extraction, which usually leads to the pulverization of silicon particles, loss of electrical contact, unstable solid electrolyte interface (SEI), and subsequent poor electrochemical cycling reversibility.
[0003] The main function of the binder is to provide strong adhesion / cohesion between silicon particles, conductive additives and current collectors to maintain the integrity of the electrode matrix during the charge / discharge process to achieve sustainable cycle performance. However, when using current binders to prepare silicon negative electrodes, there are still problems such as silicon negative electrode expansion, negative electrode active materials and SEI film shedding, which affect the battery cycle performance. Summary of the invention
[0004] In order to solve the above technical problems, the present invention provides a modified polyacrylic acid silicon negative electrode binder and a preparation method thereof and a silicon negative electrode plate. The binder of the present invention is liquid at room temperature. During the heating treatment process, as the solvent evaporates, the carboxyl group in the polyacrylic acid and the amino group in the hyperbranched amine modifier undergo an amidation reaction, and a three-dimensional network structure is formed through in-situ cross-linking, which can inhibit the expansion of the silicon negative electrode, reduce the shedding of the negative electrode active material and SEI film, and increase the battery cycle capacity retention rate.
[0005] The present invention is specifically implemented through the following technical solutions.
[0006] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0007] In a first solvent, a multifunctional amine compound and a multifunctional double-bond compound are used as raw materials, and a hyperbranched amine modifier solution is obtained through a Michael addition reaction under the action of a base catalyst.
[0008] In the second solvent, acrylic acid or methacrylic acid is used as a monomer, and under the action of an initiator, a polymerization reaction is carried out, and after neutralization, a polyacrylic acid solution is obtained.
[0009] The polyacrylic acid solution and the hyperbranched amine modifier solution are mixed evenly to obtain a modified polyacrylic acid-based silicon negative electrode binder.
[0010] The modified polyacrylic acid silicon negative electrode binder is liquid at room temperature. When subjected to vacuum heat treatment at 60°C to 180°C, as the first solvent and the second solvent evaporate, the carboxyl groups in the polyacrylic acid and the amino groups in the hyperbranched amine modifier undergo amidation reactions, cross-linking to form a three-dimensional network structure.
[0011] The flexibility of the modified polyacrylic acid binder can be adjusted by changing the composition and ratio of the multifunctional amine and the double bond in synthesizing the hyperbranched amine.
[0012] Preferably, the multifunctional amine compound is at least one of ethylenediamine, diethylenetriamine, hexamethylenediamine, tris(2-aminoethyl)amine, aniline, 1,3-propylenediamine, 1,2-propylenediamine, N,N-dimethyl-1,3-propylenediamine, p-phenylenediamine, butanediamine, pentamethylenediamine and phenylenediamine.
[0013] Preferably, the multifunctional double bond compound is at least one of divinylbenzene, N,N-methylenebisacrylamide, allyl methacrylate, diallyl phthalate, pentaerythritol triallyl ether and ethylene glycol diacrylate.
[0014] Preferably, the molar ratio of the multifunctional amine compound to the multifunctional double bond compound is 1:0.2-2, the base catalyst accounts for 0.001-0.05 of the total mass of the multifunctional amine compound and the multifunctional double bond compound, and the base catalyst is sodium ethoxide, sodium hydride, sodium amide triethylamine, dimethylphenylphosphine, tributylphosphine or diethylenetriamine.
[0015] Preferably, when preparing the hyperbranched amine modifier solution, the first solvent is one or a mixture of water, ethanol, N,N-methylpyrrolidone, and N,N-dimethylacetamide, the temperature is room temperature, and the reaction time is 6h to 24h.
[0016] Preferably, the mass ratio of polyacrylic acid to hyperbranched amine modifier is 1:0.1-1.5.
[0017] Preferably, the initiator is at least one of potassium persulfate, ammonium persulfate, sodium persulfate, tert-butyl hydroperoxide, bleaching powder, ammonium persulfate and sodium bisulfite.
[0018] Preferably, during neutralization, the neutralizing agent used is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia water. It should be noted that the preparation of polyacrylic acid is a conventional method, and the existing polyacrylic acid silicon negative electrode binder can also be used.
[0019] The present invention provides a modified polyacrylic acid silicon negative electrode binder prepared by the above-mentioned preparation method.
[0020] The present invention provides a method for preparing a silicon negative electrode sheet, comprising the following steps:
[0021] The active material, the conductive additive and the above-mentioned binder are mixed to prepare a negative electrode slurry; in the negative electrode slurry, the mass percentage of the active material is 60% to 90%, the mass percentage of the conductive additive is 5% to 20%, and the balance is the binder, which is 100% in total.
[0022] The negative electrode slurry is coated on a current collector, and after coating, a vacuum heat treatment is performed at 60° C. to 180° C. to obtain a silicon negative electrode sheet.
[0023] The present invention provides a silicon negative electrode sheet prepared by the above preparation method.
[0024] Compared with the prior art, the present invention has the following beneficial effects:
[0025] The invention uses a multifunctional amine compound and a multifunctional double-bond compound as raw materials, obtains a hyperbranched amine modifier solution through a Michael addition reaction under the action of an alkali catalyst, and uses the hyperbranched amine modifier solution to mix with a polyacrylic acid solution to prepare a modified polyacrylic acid silicon negative electrode binder. The binder is liquid at room temperature. When subjected to vacuum heat treatment at 60°C to 180°C, as the solvent evaporates, carboxyl groups in the polyacrylic acid and amino groups in the hyperbranched amine modifier undergo an amidation reaction, and are cross-linked to form a three-dimensional network structure. This property enables the binder to form a three-dimensional network structure in situ during the preparation process when preparing a silicon negative electrode, thereby inhibiting the expansion of the silicon negative electrode, reducing the shedding of negative electrode active materials and SEI films, and increasing the battery cycle capacity retention rate.
[0026] The invention can adjust the flexibility of the modified polyacrylic acid binder by changing the composition and ratio of the multifunctional amine and the double bond for synthesizing the hyperbranched amine.
[0027] The binder of the present invention has a simple preparation method. When used for preparing silicon negative electrodes, the performance of the electrode pieces can be improved without changing the pulping process, and the binder is suitable for large-scale industrial applications. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] Figure 1 It is a possible structure of a hyperbranched amine modifier.
[0029] Figure 2 Schematic diagram of in-situ cross-linking of polyacrylic acid and hyperbranched amine modifier.
[0030] Figure 3 The silicon negative electrode sheet is prepared using the modified polyacrylic acid binder prepared in Example 3.
[0031] Figure 4This is a peeling test diagram of the silicon negative electrode sheet prepared with the modified polyacrylic acid binder prepared in Example 3. DETAILED DESCRIPTION
[0032] In order to enable those skilled in the art to better understand the technical solution of the present invention and implement it, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention. The experimental methods and detection methods described in the following embodiments are conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified.
[0033] The present invention provides a method for preparing a modified polyacrylic acid silicon negative electrode binder, comprising the following steps:
[0034] In a first solvent, a multifunctional amine compound and a multifunctional double bond compound are used as raw materials, and a hyperbranched amine modifier solution (such as Figure 1 Shown is a possible structure of a hyperbranched amine).
[0035] In the second solvent, acrylic acid or methacrylic acid is used as a monomer, and under the action of an initiator, a polymerization reaction is carried out, and after neutralization, a polyacrylic acid solution is obtained.
[0036] The polyacrylic acid solution and the hyperbranched amine modifier solution are mixed evenly to obtain a modified polyacrylic acid silicon negative electrode binder. The binder is in an uncrosslinked state during homogenization. After coating, it is heated in a vacuum oven to cause in-situ crosslinking (the in-situ crosslinking mechanism is as follows Figure 2 As shown, the carboxyl groups in the polyacrylic acid react with the amino groups in the hyperbranched amine modifier solution to undergo an amidation reaction, and cross-link to form a three-dimensional network structure), thereby preparing a silicon negative electrode plate, which can inhibit the expansion of the silicon negative electrode, reduce the shedding of the negative electrode active material and SEI film, and increase the battery cycle capacity retention rate. In addition, the present invention can adjust the cross-linking degree and flexibility of the polymer by changing the molecular structure and addition amount of the hyperbranched amine to achieve compatibility with existing plate processing requirements, and the cross-linking method of the present invention is simple and safe.
[0037] Preferably, the multifunctional amine compound is at least one of ethylenediamine, diethylenetriamine, hexamethylenediamine, tris(2-aminoethyl)amine, aniline, 1,3-propylenediamine, 1,2-propylenediamine, N,N-dimethyl-1,3-propylenediamine, p-phenylenediamine, butanediamine, pentamethylenediamine and phenylenediamine.
[0038] Preferably, the multifunctional double bond compound is at least one of divinylbenzene, N,N-methylenebisacrylamide, allyl methacrylate, diallyl phthalate, pentaerythritol triallyl ether and ethylene glycol diacrylate.
[0039] Preferably, the molar ratio of the multifunctional amine compound to the multifunctional double bond compound is 1:0.2-2, the base catalyst accounts for 0.001-0.05 of the total raw material mass, and the base catalyst is sodium ethoxide, sodium hydride, sodium amide triethylamine, dimethylphenylphosphine, tributylphosphine or diethylenetriamine.
[0040] Preferably, when preparing the hyperbranched amine modifier solution, the first solvent is one or a mixture of water, ethanol, N,N-methylpyrrolidone, and N,N-dimethylacetamide, the temperature is room temperature, and the reaction time is 6h to 24h.
[0041] Preferably, the mass ratio of polyacrylic acid to hyperbranched amine modifier is 1:0.1-1.5.
[0042] Preferably, the initiator is at least one of potassium persulfate, ammonium persulfate, sodium persulfate, tert-butyl hydroperoxide, bleaching powder, ammonium persulfate and sodium bisulfite.
[0043] Preferably, during neutralization, the neutralizing agent used is one or more of sodium hydroxide, potassium hydroxide, lithium hydroxide, and ammonia water.
[0044] The adhesive of the present invention can be used to prepare a lithium ion battery negative electrode and a corresponding lithium ion battery. The preparation process of the lithium ion battery includes the following steps:
[0045] The negative electrode active material, the conductive additive and the binder are mixed in proportion, and are evenly dispersed in deionized water by ball milling to obtain a uniformly mixed negative electrode slurry, wherein the mass percentage of the active material in the negative electrode slurry is 60% to 90%, the mass percentage of the conductive additive is 5% to 20%, and the remainder is the binder, which is 100% in total; the active material is silicon nanoparticles, the conductive additive is acetylene black, and the binder is the binder of the present invention.
[0046] The negative electrode slurry is evenly coated on a 12-micron thick copper foil with an automatic coating machine, with a coating thickness of 50 microns, and then placed in a vacuum drying oven to dry and remove the solvent, and then heated to 60°C to 180°C and cross-linked for 2 hours. After drying, it is cut into negative electrode sheets with a diameter of 12 mm.
[0047] The prepared electrode sheet was transferred to a glove box filled with argon and assembled into a 2032 button half-cell. A lithium sheet was used as the counter electrode and a Celgard 2325 polypropylene-polyethylene-polypropylene (PP-PE-PP) membrane was used as the separator. The electrolyte was a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1) containing 1M lithium hexafluorophosphate (LiPF6), and 10% volume fraction of fluoroethylene carbonate (FEC) was added.
[0048] The assembled button cell was left to stand for 10 h, then cycled at a rate of 0.1C within a voltage range of 0.01V-2.00V for one week, and then charged and discharged at a rate of 0.3C.
[0049] The technical solution of the present invention is further described below in conjunction with the embodiments and the attached tables.
[0050] Example 1
[0051] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0052] 4 g (25.9 mmol) of N,N-methylenebisacrylamide, 6 g (51.63 mmol) of hexamethylenediamine, 0.1 g of sodium ethoxide and 90 g of water were added to a single-necked flask, and the mixture was stirred under magnetic stirring at room temperature for 8 h to obtain a hyperbranched amine solution.
[0053] In a three-necked flask, add 10 g of acrylic acid, 90 g of water, and 0.1 g of APS, mix and stir, react at 80° C. for 6 h, and then neutralize with ammonia water to obtain a neutralized polyacrylic acid solution.
[0054] 10 g of the hyperbranched amine solution and 10 g of the polyacrylic acid solution were mixed evenly under magnetic stirring. The resulting binder was marked as A1.
[0055] Example 2
[0056] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0057] 4 g (25.9 mmol) of N,N-methylenebisacrylamide, 6 g (51.63 mmol) of hexamethylenediamine, 0.1 g of sodium ethoxide and 90 g of water were added to a single-necked flask, and the mixture was stirred under magnetic stirring at room temperature for 8 h to obtain a hyperbranched amine solution.
[0058] In a three-necked flask, add 10 g of acrylic acid, 90 g of water, and 0.1 g of APS, mix and stir, react at 80° C. for 6 h, and then neutralize with ammonia water to obtain a neutralized polyacrylic acid solution.
[0059] 5 g of the hyperbranched amine solution and 10 g of the polyacrylic acid solution were mixed evenly under magnetic stirring. The resulting adhesive was marked as A2.
[0060] Example 3
[0061] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0062] 4 g (25.9 mmol) of N,N-methylenebisacrylamide, 6 g (51.63 mmol) of hexamethylenediamine, 0.1 g of sodium ethoxide and 90 g of water were added to a single-necked flask, and the mixture was stirred under magnetic stirring at room temperature for 8 h to obtain a hyperbranched amine solution.
[0063] In a three-necked flask, add 10 g of acrylic acid, 90 g of water, and 0.1 g of APS, mix and stir, react at 80° C. for 6 h, and then neutralize with ammonia water to obtain a neutralized polyacrylic acid solution.
[0064] 1 g of the hyperbranched amine solution and 10 g of the polyacrylic acid solution were mixed evenly under magnetic stirring. The resulting adhesive was marked as A3.
[0065] Example 4
[0066] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0067] 4 g (23.5 mmol) of ethylene glycol diacrylate, 6 g (41.03 mmol) of tris(2-aminoethyl)amine, 0.1 g of sodium ethoxide and 90 g of water were added to a single-necked flask, and the mixture was stirred under magnetic stirring at room temperature for 8 h to obtain a hyperbranched amine solution.
[0068] In a three-necked flask, add 10 g of acrylic acid, 90 g of water, and 0.1 g of APS, mix and stir, react at 80° C. for 6 h, and then neutralize with ammonia water to obtain a neutralized polyacrylic acid solution.
[0069] 5 g of the hyperbranched amine solution and 10 g of the polyacrylic acid solution were mixed evenly under magnetic stirring. The resulting adhesive was marked as A4.
[0070] Example 5
[0071] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0072] 4 g (25.9 mmol) of N,N-methylenebisacrylamide, 0.62 g (5.3 mmol) of hexamethylenediamine, 0.04 g of triethylamine and 41.58 g of water were added to a single-necked flask, and the mixture was stirred under magnetic stirring at room temperature for 8 h to obtain a hyperbranched amine solution.
[0073] In a three-necked flask, add 10 g of acrylic acid, 90 g of water, and 0.1 g of APS, mix and stir, react at 80° C. for 6 h, and then neutralize with ammonia water to obtain a neutralized polyacrylic acid solution.
[0074] 3 g of the hyperbranched amine solution and 10 g of the polyacrylic acid solution were mixed evenly under magnetic stirring. The resulting adhesive was labeled A6.
[0075] Example 6
[0076] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0077] 4 g (31.7 mmol) of allyl methacrylate, 3.428 g (31.7 mmol) of p-phenylenediamine, 0.07 g of sodium ethoxide and 66.85 g of water were added to a single-necked flask, and the mixture was stirred under magnetic stirring at room temperature for 8 h to obtain a hyperbranched amine solution.
[0078] In a three-necked flask, add 10 g of acrylic acid, 90 g of water, and 0.1 g of APS, mix and stir, react at 80° C. for 6 h, and then neutralize with ammonia water to obtain a neutralized polyacrylic acid solution.
[0079] 1 g of the hyperbranched amine solution and 10 g of the polyacrylic acid solution were mixed evenly under magnetic stirring. The resulting adhesive was labeled A6.
[0080] Example 7
[0081] A method for preparing a modified polyacrylic acid silicon negative electrode binder comprises the following steps:
[0082] 7.81 g (31.7 mmol) of diallyl phthalate, 1.40 g (31.7 mmol) of dibutylene diamine, 0.092 g of sodium ethoxide and 82.89 g of water were added to a single-necked flask, and the mixture was stirred under magnetic stirring at room temperature for 8 h to obtain a hyperbranched amine solution.
[0083] In a three-necked flask, add 10 g of acrylic acid, 90 g of water, and 0.1 g of APS, mix and stir, react at 80° C. for 6 h, and then neutralize with ammonia water to obtain a neutralized polyacrylic acid solution.
[0084] 2 g of the hyperbranched amine solution and 10 g of the polyacrylic acid solution were mixed evenly under magnetic stirring. The resulting adhesive was labeled A6.
[0085] Comparative Example 1
[0086] A method for preparing a polyacrylic acid silicon negative electrode binder comprises the following steps:
[0087] In a three-necked flask, 10 g of acrylic acid, 90 g of water, and 0.1 g of APS were added, mixed, and stirred, reacted at 80° C. for 6 h, and then neutralized with ammonia water to obtain a neutralized polyacrylic acid solution. The obtained adhesive was marked as A5.
[0088] The binders prepared in Examples 1 to 7 and Comparative Example 1 are used to prepare lithium ion batteries, which specifically includes the following steps:
[0089] (1) A negative electrode active material, a conductive additive and a binder are mixed in proportion and uniformly dispersed in deionized water by ball milling to obtain a uniformly mixed negative electrode slurry, wherein the mass percentage of the active material in the negative electrode slurry is 80%, the mass percentage of the conductive additive is 10%, and the remainder is a binder, which is 100% in total; the active material is silicon nanoparticles, the conductive additive is acetylene black, and the binder is the binder prepared in Examples 1 to 7 and Comparative Example 1.
[0090] (2) The slurry in step (1) is evenly coated on a 12 μm thick copper foil using an automatic coating machine to a coating thickness of 50 μm, and then placed in a vacuum drying oven to dry to remove the solvent, and then heated to 150° C. and cross-linked for 2 hours. After drying, it is cut into negative electrode sheets with a diameter of 12 mm. Figure 3 The silicon negative electrode sheet is prepared using the modified polyacrylic acid binder prepared in Example 3.
[0091] (3) The electrode sheet prepared in step (2) was transferred to a glove box filled with argon and assembled into a 2032 button half-cell. A lithium sheet was used as the counter electrode and a Celgard 2325 polypropylene-polyethylene-polypropylene (PP-PE-PP) membrane was used as the separator. The electrolyte was a mixed solution of ethylene carbonate (EC) and diethyl carbonate (DEC) (volume ratio of 1:1) containing 1M lithium hexafluorophosphate (LiPF6), and 10% volume fraction of fluoroethylene carbonate (FEC) was added.
[0092] (4) The button cell assembled in step (3) was left to stand for 10 h, and then cycled for one week at a rate of 0.1C within a voltage range of 0.01 V to 2.00 V, and then charged and discharged at a rate of 0.3C. The specific data are shown in Table 1.
[0093] Table 1 Electrochemical performance data of the binder of Examples 1 to 7 and Comparative Example 1
[0094] serial number Capacity maintenance rate after 100 weeks (%) First week efficiency (%) Example 1 75.3 89.9 Example 2 77.6 89.5 Example 3 91.4 90.2 Example 4 86.2 88.7 Example 5 65.6 87.7 Example 6 81.4 88.9 Example 7 79.5 88.3 Comparative Example 1 65.4 88.5
[0095] It can be seen from the results in Table 1 that, compared with the polyacrylic acid binder prepared in Comparative Example 1, the binder prepared in the present invention can inhibit the expansion of the silicon negative electrode, reduce the shedding of the negative electrode active material and SEI film, and increase the battery cycle capacity retention rate. Figure 4The figure is a peeling test diagram of the silicon negative electrode sheet prepared by the modified polyacrylic acid binder prepared in Example 3. The present invention provides a new binder, which modifies the polyacrylic acid binder by a hyperbranched amine modifier to adjust the flexibility of the polyacrylic acid binder. In addition, the binder of the present invention is in an uncrosslinked state (liquid state) when homogenized. After coating, it is heated in a vacuum oven to crosslink in situ, and a three-dimensional network structure is formed in situ in the silicon negative electrode, which can inhibit the expansion of the silicon negative electrode, reduce the shedding of the negative electrode active material and SEI film, and increase the battery cycle capacity retention rate.
[0096] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, they are also intended to be included.
Claims
1. A method for preparing a modified polyacrylic acid silicon negative electrode binder, characterized in that: The following steps are involved: In a first solvent, a multifunctional amine compound and a multifunctional double bond compound are used as raw materials, and a hyperbranched amine modifier solution is obtained through a Michael addition reaction under the action of a base catalyst; In a second solvent, acrylic acid or methacrylic acid is used as a monomer, and under the action of an initiator, a polymerization reaction is carried out, and after neutralization, a polyacrylic acid solution is obtained; The polyacrylic acid solution and the hyperbranched amine modifier solution are uniformly mixed to obtain a modified polyacrylic acid-based silicon negative electrode binder; The modified polyacrylic acid silicon negative electrode binder is liquid at room temperature. When subjected to vacuum heat treatment at 60°C to 180°C, as the first solvent and the second solvent evaporate, the carboxyl groups in the polyacrylic acid and the amino groups in the hyperbranched amine modifier undergo amidation reactions, cross-linking to form a three-dimensional network structure.
2. The method for preparing the modified polyacrylic acid silicon negative electrode binder according to claim 1, characterized in that: The polyfunctional amine compound is at least one of ethylenediamine, diethylenetriamine, hexamethylenediamine, tris(2-aminoethyl)amine, aniline, 1,3-propylenediamine, 1,2-propylenediamine, N,N-dimethyl-1,3-propylenediamine, p-phenylenediamine, butanediamine, pentamethylenediamine and phenylenediamine.
3. The method for preparing the modified polyacrylic acid silicon negative electrode binder according to claim 1, characterized in that: The multifunctional double bond compound is at least one of divinylbenzene, N,N-methylenebisacrylamide, allyl methacrylate, diallyl phthalate, pentaerythritol triallyl ether and ethylene glycol diacrylate.
4. The method for preparing the modified polyacrylic acid silicon negative electrode binder according to claim 1, characterized in that: The molar ratio of the multifunctional amine compound to the multifunctional double bond compound is 1:0.2-2, the base catalyst accounts for 0.001-0.05 of the total mass of the multifunctional amine compound and the multifunctional double bond compound, and the base catalyst is sodium ethoxide, sodium hydride, sodium amide triethylamine, dimethylphenylphosphine, tributylphosphine or diethylenetriamine.
5. The method for preparing the modified polyacrylic acid silicon negative electrode binder according to claim 1, characterized in that: When preparing the hyperbranched amine modifier solution, the first solvent is one or a mixture of water, ethanol, N,N-methylpyrrolidone, and N,N-dimethylacetamide, the temperature is room temperature, and the reaction time is 6 hours to 24 hours.
6. The method for preparing the modified polyacrylic acid silicon negative electrode binder according to claim 1, characterized in that: The mass ratio of polyacrylic acid to the hyperbranched amine modifier is 1:0.1-1.
5.
7. The modified polyacrylic acid silicon negative electrode binder prepared according to the preparation method according to any one of claims 1 to 6.
8. A method for preparing a silicon negative electrode sheet, characterized in that: The following steps are involved: The active material, the conductive additive and the binder according to claim 7 are mixed to prepare a negative electrode slurry; in the negative electrode slurry, the mass percentage of the active material is 60% to 90%, the mass percentage of the conductive additive is 5% to 20%, and the balance is the binder, which is 100% in total; The negative electrode slurry is coated on a current collector, and after coating, a vacuum heat treatment is performed at 60° C. to 180° C. to obtain a silicon negative electrode sheet.
9. The silicon negative electrode sheet prepared by the preparation method according to claim 8.